MARCO AND LOUISE MITRANIDEPARTMENT OF DESERT ECOLOGY2Clockwise from upper left:

The ibex (Capra ibexnubiana) lives in themountains of the Negev,in the Rift Valley andJudean desert.

Black widow spiders(Latrodectus revivensis)are a dominantcomponent of web-building spiders in theNegev highlands.

Bacteria that usepolyethylene as their solecarbon source mayprovide a solution todisposing of polyethylenewaste used in AravaValley protectedagriculture shown above.

The poplar (Populuseuphratica) is found nearwater sourcesthroughout Israel and ina few places in the Negevhighlands, including EinAvdat in Nahal Zin.

desertecology 25

MARCO AND LOUISE MITRANIDEPARTMENT OFDESERT ECOLOGY

Prof.Yael Lubin, Chair

Researchers in the Mitrani Department of Desert Ecology use deserts as model ecosystemsfor advancing the study of ecology in general, and the ecology of Israeli deserts in particular.Our findings can aid the conservation of desert ecosystems and can be applied to theprudent and sustainable development of desert regions.

A major departmental project deals with the conservation and maintenance of biodiversityin arid lands.This research includes studies to assess environmental heterogeneity (bothphysical and biological), ecological transformations (natural and man-caused), and bioticinteractions (such as predation, parasitism, and competition for resources).The roles of scaleand the mechanisms involved in creating and maintaining the diverse patterns of variousdesert plants and animals are also major topics of investigation.

The range of subjects covered by departmental staff and students includes: investigations inphysiological ecology, behavioral ecology and life histories, population ecology and genetics,and community and landscape ecology. Studies in applied ecology, in collaboration with theJewish National Fund (JNF) and other organizations, investigate the implications of regionaldevelopment projects, methods of arresting desertification, and the rehabilitation oflandscapes degraded by human activity.

The Mitrani Department facilities include animal rooms and outdoor cages, a referenceherbarium, areas for garden experiments in loess and sandy desert soils, outdoor insecthouses, and research sites representing a variety of desert habitats.Three peripheral researchcenters are affiliated with the Department:The Ramon Science Center (Mitzpe Ramon), theHazeva Research and Development Center (Hazeva,Arava Valley), and the Desertification andRestoration Ecology Research Center (Sede-Boqer Campus), established jointly with the JNF.

Phone: 972-8-659-6771 • Fax: 972-8-659-6772 • E-mail: mitrani@bgumail.bgu.ac.il

Academic StaffAbramsky, Zvika1

Ayal,YoramBouskila,Amos2

Kotler, Burt P.Lubin,Yael D.Novoplansky,ArielPinshow, Berry1

Safriel, Uriel N.Saltz, DavidShachak, Moshe Ward, David3

Ziv,Yaron2

ASsociate StaffYarom, Ilan Zaady, Eli

1 Joint appt. with BGU’s Dept. of Life Sciences2 Home department – BGU’s Dept. of Life Sciences3 Now at Stellenbosch University, South Africa

Palestine sunbird (Nectariniaosea), a common nectar feeder in

Israel. It has a very frugalnitrogen balance and has been the

subject of several behavioral andphysiological studies by faculty

and students.

desertecology 26

DIETARY ENERGETICS AND

COMMUNITY ECOLOGY OF

DESERT INSECTIVOROUS BATS

PINSHOW

AMMONOTELY: THE

COMPOSITION OF AVIAN

URINE CHANGES IN

RESPONSE TO BOTH

TEMPERATURE AND

NITROGEN INTAKE

PINSHOW

Research Activities

Physiological Ecology

Desert organisms often have specialized physiological responses not observed in speciesresiding in temperate climates. Departmental researchers investigate the influence ofenvironment on the respiratory physiology, water loss and energy budgets of desert birdsand small mammals – and how these traits influence the community structures of organisms.

The energetic requirements of organisms influence the composition and diversity of speciesin the community. Desert bats are likely to be severely restricted by food availability.We havecharacterized the foraging habitats of insectivorous bats in the Negev in order to select twocommon species with different life history characteristics for a comparative study of theirenergy requirements.We surveyed bats in the central Negev highland using mist-nets tocapture individuals and acoustic monitoring for vocal identification.Altogether, we capturedor vocally identified 10 bats species during foraging and found that insectivorous bats foragein all the habitats except for sandy landscapes. Four species (Rhinolophus hipposideros,Rhinolophus clivosus, Plecotus austriacus, Otonycteris hemprichii) were found at sites with densevegetation cover and three species (Pipistrellus kuhlii, Pipistrellus bodenheimeri, Eptesicus bottae)at sites with less-dense vegetation. P. kuhlii and E. bottae also forage around light poles and P.kuhlii, around artificial water sources. Tadarida teniotis and Taphozous nudiventris forage aroundlight poles. T. teniotis forage in all the sites, but mainly around artificial lights. Rhinopomamicrophyllum was found in the research area, but we do not yet know where it forages.Theseobservations suggest that the selection of foraging habitats by the different species iscorrelated with their maneuverability in flight as well as their echolocation call patterns.Based on our results,we chose Otonycteris hemprichii, the most common gleaning species, andTadarida teniotis, the most common aerial feeder, for further studies of ecological energetics.With: C. Korine

Uricotely (excretion of uric acid comprising more than 50% of urinary nitrogen) in birds wasonce considered ubiquitous. However, Anna’s hummingbirds (Calypte anna) were recentlyshown to be an exception to this rule: under conditions of low ambient temperature and ona nitrogen-free diet, they increased their water intake and often became ammonotelic(excreting largely ammonia).We studied the effects of nitrogen intake, water intake andambient temperature (Ta) on ammonotely in birds.We also wished to determine whetherammonotely was restricted to small nectar-feeding birds such as Palestine sunbirds (Nectariniaosea) or whether it is a more general phenomenon.Therefore, we assayed ureteral urinecomposition in eight yellow-vented bulbuls (Pycnonotus xanthopygos), each randomly allocateda diet of 20% (0.6 M) sucrose solution supplemented by either 1.03 g/l or 7.23 g/l soy protein,and held at a Ta of either 28ºC or 10ºC. Food- and thus water-intake rates varied withnitrogen intake but not with ambient temperature. Food intake increased significantly withdecreased nitrogen intake.While concentrations of all the excretory compounds in the urinedecreased, the relative proportions of ammonia, urea and uric acid in the urine did not changesignificantly. The lower ambient temperature had no effect on food intake or on theconcentration of uric acid.However, at 10ºC the urea and uric acid concentrations in the urineincreased and led to a significant increase in the relative proportions of ammonia and urea.Our results suggest that, whenever birds with high metabolic and water turnover rates areexposed to low ambient temperature, ammonotely or a shift towards ammonotely will occur.With: I.G. van Tets, C. Korine, L. Roxburgh

desertecology 27

EFFECTS OF FASTING ON IN-

FLIGHT FUEL CATABOLISM

OF PIGEONS

Pinshow

INFORMATION PROCESSING

AND DEVELOPMENTAL

INTEGRATION IN PLANTS

Novoplansky

Some birds regularly undergo extended fasts and many maintain high-metabolic activity, suchas migratory flight, while fasting.We investigated the effects of fasting on the metabolism ofenergy substrates in flight by depriving trained tippler pigeons (Columba livia) of food for2 - 48 hours preceding flights of 4 hours. Immediately after flight, blood concentrations of uricacid and β-hydroxybutyrate were increased, indicating elevated protein and lipid catabolismduring flight. Lighter birds and birds that fasted for longer periods before a flight, lost lessmass during a 4-hour flight than heavier ones and those that fasted for shorter periods. Birdsthat lost more body mass during flight had lower blood b-hydroxybutyrate concentrations,suggesting lower in-flight lipid oxidation. Flying pigeons apparently did not compensate forlower lipid catabolism by increasing proteolysis. Changes in in-flight protein catabolism werenot correlated with either fast duration or preflight body mass.We reasoned that pigeonslost more mass in-flight after feeding than after fasting because recently fed birds catabolizedmore glycogen.Thus, the preflight fast duration is an important determinant of the fuels usedin flight.With: L.Z. Gannes, K.A. Hatch, BIDR

BEHAVIORAL ECOLOGY AND LIFE HISTORIES

Organisms have different means of coping with marked seasonal changes in resourceabundance and the very low abundance typical of many desert ecosystems.They may modifytheir behavior or their life history and demographic strategies – namely, by adjusting aspectsof growth, reproduction and dispersal.Mitrani researchers examine the growth “decisions” ofplants under different environmental regimes and the ways that various animals makedecisions about foraging and development – and the life-history consequences of thesedecisions.

PLANT DEVELOPMENTAL DECISIONS

Developmental plasticity can be defined as the ability to execute developmental decisionsbased on perceived information.Developmental plasticity plays a major role in the adaptationof plants to heterogeneous environments because of their limited motility and lack ofcognition.This research fills the gaps separating the physiological, ecological and evolutionaryapproaches. While we emphasize adaptations and behaviors of individual plants,developmental plasticity also has consequences at higher organizational levels. Ourinterdisciplinary and multihierarchical approach can advance the understanding of plantadaptation to changing environments.

Plants constantly perceive and integrate external information regarding present andexpected resource levels with internal information regarding the function and relativesuccess of different organs that grow on the plant. By integrating this information plants areable to allocate limited resources to more successful organs – organs that develop in morepromising patches or those that are more vigorous and are expected to contribute more tothe plant’s long-term success. In addition, if the growth of different organs is correlated, theplant may avoid competition with its own organs and thus increase its performance by, forexample, allocating more resources to organs that compete with neighboring plants.Thus, thesame mechanisms provide the plant with efficient self-organization as well as with betterperformance in the presence of competitors. Since developmental processes take time,plantsmay adjust to expected environmental changes through the utilization of signals (for example,the ratio of light in the red and far-red wavelengths) that are correlated with conditions thatinfluence development long before these conditions are actually experienced. But inagricultural systems, early perception and reaction could result in inefficiencies.To overcomesuch problems, the altering of spectral signals in horticultural systems could be used totrigger sun-loving crop plants to change their growth pattern, thereby enhancing theproduction of leaves, flowers and fruits at the expense of organs of lesser horticultural value.

In the ecological growth facility,Mitrani researchers investigatethe growth ‘decisions’ of plantsunder different environmental

regimes.

desertecology 28

PLASTICITY OF

DEVELOPMENTAL

HIERARCHIES IN PLANTS

Novoplansky,

CONSEQUENCES OF

DEVELOPMENTAL PLASTICITY

AT HIGHER

ORGANIZATIONAL LEVELS

Novoplansky

SQUIRRELS AS FUTURES

TRADERS: CACHING

BEHAVIOR, STATE-

DEPENDENT FORAGING AND

LIFE EXPECTANCY

Kotler

The most common and ecologically important expression of developmental plasticity inplants is size variation. Not only do size differences result from differences in organ numberand/or size but also from their “telescopic hierarchy”: larger organs not only consist of moremodular units of the same size, but they provide the infrastructure for additional modules oflower hierarchies.Thus plants possess a plasticity that influences both the size and number ofa wide variety of organs that are hierarchically constructed, e.g., leaves on branches withinlarger branches or shoot systems, and flowers within inflorescence units within a largeinflorescence. The hypothesis underlying this theory is that the hierarchical nature ofdevelopment provides plants with the ability to respond to environmental signals or changesthrough formation of organs of a different size, a major kind of developmental plasticity thatis expressed by size relationships among different parts of the same plant rather than that ofthe plant as a whole.

Very little is known about the consequences of plant developmental plasticity for population-and community-level interactions. Even when developmental plasticity is significant for theperformance of individual plants, it will be meaningful for population- and community-levelprocesses only if different members of the population (e.g., plants of various ages) or of thecommunity utilize different levels or types of plasticity. Developmental plasticity may be ofgreat consequence for community-level interactions when resources are supplied in pulsesrather than continuously. In many unproductive environments, plants experience two phasesof resource availability: “pulse periods” in which resources are high and most growth andresource accumulation occur and “interpulse periods” in which resources are too low formost plants to take up and mortality due to resource deficits increases. According to the“two-phase resource dynamics hypothesis,” the effects of competition on growth shouldoccur during pulses at both high and low productivity. In productive environments, interpulseintervals should be relatively mild and infrequent and therefore competitive effects duringpulses will usually be important for individual and population persistence. However, asproductivity in an environment decreases, the frequency and magnitude of pulses oftendecrease and the duration of interpulse periods increases. In this situation, it is suggested,processes occurring during interpulse intervals become increasingly important for individualand population persistence.

FORAGING DECISIONS

Animals that cache food have a personal futures market. This fact can connect threeimportant, largely independent lines of ecological knowledge: caching behavior, state-dependent foraging and life expectancy.When a food item can be cached, it has present valueif consumed immediately and future value if cached in anticipation of future needs.The stateof a forager (young versus old, well off versus desperate, high- versus low-survivorshipprospects) should influence present value, future value and, hence, caching behavior. Futurevalue should improve with the likelihood of future need – that the cached food item will beavailable in the future (subject to decay, pilferage and loss), and that the animal will be alive touse it.This research continues the theoretical modeling of the connection between cachingbehavior, the animal state and survivorship. Caching animals can reveal life expectancy by theway they balance present and future value. Using fox squirrels (Sciurus niger), we tested theoccurrence of different foraging strategies with cacheable versus noncacheable foods.All elsebeing equal, foraging should concentrate on cacheable rather than noncacheable foods.Animals in a low-quality state should be less sensitive to predation risk.Animals with low-survivorship expectation should place relatively more value on the present than on the futurewhen compared with those with high-survivorship expectations. Finally, cacheable foodsshould have their highest value relative to noncacheable foods during the season just prior toimminent needs. Squirrels ate more cacheable food (hazelnuts in their shells) thannoncacheable food (hazelnuts with shells removed).This result cannot be explained solely byhigher encounter rates of hazelnuts with shells.These results demonstrate that such food ismore valuable and that squirrels respond to the future value of their food.With: J.S. Brown, M. van de Merve, University of Illinois, Chicago

desertecology 29

FORAGING GAMES BETWEEN

GERBILS AND THEIR

PREDATORS: TEMPORAL

DYNAMICS OF RESOURCE

DEPLETION AND

APPREHENSION IN GERBILS

KOTLER, BOUSKILA

SHORT- AND LONG-TERM

EFFECTS OF SIMULATED FULL

MOONLIGHT ON THE

FORAGING ACTIVITY OF

GERBILS

KOTLER, BOUSKILA

THE COSTS OF APPREHENSIVE

FORAGING

ABRAMSKY

Predator-prey interactions constitute a foraging game when prey individuals manage riskfrom predators and predator individuals manage fear in their prey.As tools for managing risk,clever prey can use apprehension and redirect attention from foraging to predator detection.One such foraging game occurs between gerbils and their predators on the sand dunes of theNegev Desert. Here, interacting species of gerbils compete for patches of seeds that renewdaily by afternoon winds. In such a situation, gerbils are expected to deplete resource patchesover the course of the night, the predators are expected to hunt when gerbil activity ishighest, and gerbils are expected to be most apprehensive when predators are most activeand most lethal.We tested these predictions for gerbils in two field experiments using seedtrays to measure patch depletion and apprehension over the course of the night, between thebush and open microhabitats, and at four moon phases (new, half-waxing, full, and half-waning). Gerbils depleted seed resources more quickly in the bush than in the openmicrohabitat, and more quickly at the new moon than at other moon phases. Gerbil activityat new moon was high throughout most of the night, but decreased towards dawn. Incontrast, activity at full moon was generally low, but increased towards dawn.The two gerbilspecies, Gerbillus andersoni allenbyi and G. pyramidum, partitioned the night, with G. pyramidumvisiting resource patches earlier in the night and encountering a richer, but more riskyenvironment, and G. a. allenbyi foraging later in an environment characterized by fewer seedresources but lower risk.The same pattern extended over moon phases, with G. pyramidumforaging relatively more at full and waning half moon. Apprehension by gerbils was higherearly in the night than later and higher at full moon than new moon. Schedules ofapprehension changed according to moon phase and may have differed between the twogerbils. Finally, apprehension was higher in the open microhabitat, although the opposite wastrue at the beginning of the night.This foraging game affects three trophic levels, including theeffect of the gerbils on the availability and distribution of seeds, the competitive interactionbetween the two gerbil species, and the predator-prey interaction between gerbils and owls.With: J.S. Brown, University of Illinois, Chicago.

We tested experimentally, in the field, the response of two gerbil species (Gerbillus allenbyi andG. pyramidum) to long-term (three-month) simulated illumination of full moon light.Thegerbils responded by leaving food patches earlier, by lowering their activity in the experimentrelative to the control subplots and by biasing their activity to the bush microhabitat.Themagnitude of the response did not diminish with time.Total activity declined, shifted towardthe bush microhabitat, and GUD rose with proximity to the light source.These results arevery similar to those obtained in short-term studies.The cumulative effect of the treatmentchanged the relative use of the subplots by the two species.While the relative use of theexperimental subplots by G. pyramidum decreased, it stayed constant for G. allenbyi.

We used a behavioral bioassay in the form of the foraging behavior of Gerbillus allenbyi and theideal free distribution to estimate the costs associated with risk of predation. Experimentsinvolved two pairs of 2-ha field enclosures. Risk of predation was introduced to one 1-hasubplot of each pair of enclosures either by simulating the light of a full moon or by causingtrained owls to fly over the subplots.We used a titration method to estimate the energeticcosts associated with risk of predation.We added seeds to the 1-ha subplot of each enclosureunder risk of predation.The adjacent subplot served as the control.Without seed addition, thesubplot without risk of predation had more foraging activity than the subplot with risk: theforagers were avoiding the risk of predation. As the amount of seeds in the treatmentincreased, the gerbils responded smoothly and quantitatively, shifting their foraging activity tothe subplot with seeds (and risk).At addition rates of 4.24 - 8.47 g seeds/individual/ha/nightand 4.24 - 5.64 g seeds/individual/ha/night, the seed addition compensated for the extra riskin the simulated moonlight and owl-flights treatments, respectively.At these rates the foragingactivity on the two subplots of each enclosure were the same. Our results suggested thatwhen challenged by the threat of predation, G. allenbyi spent at least 25% of their foragingtime being vigilant.With: M. Rosenzweig, University of Arizona,Tucson;A. Subach, Ben-Gurion University

In the aviary, researchersinvestigate predator behavior of

barn owls (Tyto alba).

desertecology 30

MEASURING BENEFITS OF

HABITAT SELECTION

ABRAMSKY

THE ENERGETIC COST OF

COMPETITION: GERBILS AS

MONEYCHANGERS

ABRAMSKY

THE COST OF INTERFERENCE

COMPETITION IN TWO

GERBIL SPECIES

ABRAMSKY

POPULATIONS, COMMUNITIES AND ECOSYSTEMS

Populations, communities and ecosystems are the three levels of ecologic organization inwhich individual organisms must operate. In deserts, processes controlling and affecting theselevels are often considered to be simpler than in more mesic regions. However, Mitraniresearchers investigating patterns and processes operating at these scales find that desertsare more complex than expected.

HABITAT SELECTION AND COMPETITON

We used a behavioral assay to estimate the advantages to two gerbil species (Gerbillus allenbyiand G. pyramidum) of preferring forging in a semistabilized dune habitat over a stabilized sandhabitat.We used the magnitude of foraging by the gerbils to monitor the difference betweenthe two habitats.When the burrowing rodents foraged as much in stabilized sand as insemistabilized dune, we inferred that these habitats were providing equivalent rewards.Weperformed a series of experiments in two 1-ha field enclosures, each containing similarproportions of stabilized sand and semistabilized dune. Each enclosure contained apopulation of only one of the species. By varying the amount of seeds added (either 0.5, 1, 2or 3 g of seeds in 18 seed-trays) to each habitat and following gerbil behavior, we were ableto fit a curve that reflected the change in habitat preference as a function of seed-additionrate.We could determine the quantity of seed addition required to bring the two habitatsinto equal use. Each species required only 13 g/ha/night to offset entirely the advantage of thesemistabilized dune.With: M. Rosenzweig, University of Arizona,Tucson;A. Subach, Ben-Gurion University

Using behavioral bioassays, we measured the costs of both inter- and intraspecificcompetition to a foraging gerbil, Gerbillus allenbyi. The bioassay is the amount of foragingactivity in field enclosures of 2 ha, and the difference between foraging activity in anexperimentally manipulated 1-ha subplot compared to the nearby, matched, unmanipulatedtwin 1-ha plot.Application of this bioassay assumes that natural selection has fitted gerbils toassess the comparative values of feeding opportunities and competitive pressures, despitetheir presentation in different currencies.The gerbils were found to perform quantitativelyand consistently, smoothly adjusting their foraging effort to the combination of disparateopportunities and costs. Measuring their responses as behavior allowed us to estimate thecosts of competition in the currency of energy flow, that is, the rate at which we added seedsto the subplots.With: M. Rosenzweig, University of Arizona,Tucson;A. Subach, Ben-Gurion University

In 1993, Ziv et al. and Kotler et al. reported that the two common granivorous gerbil speciesGerbillus allenbyi and G. pyramidum, which coexist in the sand dunes of the Israeli Negev,exhibit temporal partitioning in their foraging activity.The bigger species, G. pyramidum,aggressively displaces the smaller species during the early hours of the night.We examinedthe change in the activity pattern of G. allenbyi in pure and mixed populations in two 1-ha fieldenclosures.We confirmed the temporal pattern reported previously and also measured howmuch energy it takes (in g of millet seeds) to compensate for the costs associated withinterference, by adding millet seeds to 18 seed trays in the enclosure.We added 1, 3, 5, 7 or9 g of seeds to the seed-tray, mixing the seeds in each tray with 2 l of sand. It took 3 - 5 g ofseeds/seed-tray (1.8 - 3 g seeds/day/ha/individual) to completely overcome the interferenceby G.pyramidum; this is a measure of the costs of interference by G.pyramidum in the currencyof millet seeds.The result suggests that there is a trade-off between interference competitionand food to which gerbils respond behaviorally. It seems that the cost of interferencecompetition is much lower than the cost reported for risk of predation.With: M. Rosenzweig, University of Arizona,Tucson;A. Subach, Ben-Gurion University

desertecology 31

TENEBRIONID BEETLE

ABUNDANCE

AYAL

ABUNDANCE OF SPIDERS

LUBIN

META-POPULATION

DYNAMICS OF THE MED-FLY

IN THE JUDEAN DESERT AND

CENTRAL NEGEV HIGHLANDS

Ayal

CONSEQUENCES OF

FORAGING BEHAVIOR ON

THE DYNAMICS OF HOST-

PARASITOID INTERACTIONS

AYAl

LONG-TERM STUDIES OF ARTHROPOD POPULATIONS AND PRECIPITATION

Tenebrionid (darkling) beetles are members of a well-known group of desert-dwellingarthropods.They are both abundant and species-rich in all desert habitats and can be easilycaptured by simple pitfall traps.They are thus an ideal family of insects for the long-term studyof population abundance.The current project was started in 1989 and – except for a two-year break (1994-6) – it has been running continuously for the last 12 years. In 1994,Ayalsuggested that in the univoltine, herbivorous mirid bug, there is a yearlong time lag betweenprecipitation fluctuations and the response of the bug population. However, longer time lagsare expected for a herbivore with a longer life cycle.As the tenebrionid life cycle is between1 and 3 years, depending on species, we would expect that different time lags wouldcharacterize the various species. Having gathered population data over 10 yrs, which werehighly variable in the amount of precipitation,we are now analyzing the data to determine theexpected time lags.With:V. Subba Rao

We monitored populations of two species of web-building spiders commonly found in thecentral Negev desert: a species of desert widow spider (Latrodectus revivensis) (for 7 years)and the eresid family-spider, Stegodyphus lineatus (for 4 years).The former arachnid is apredator of ground-dwelling arthropods (tenebrionid beetles, scorpions, solifuges, desertisopods and ants), while the latter preys on flying insects (for example, cicadas, flies, wasps).Thus, these two species provide data on the response of predators to two different kinds ofprey, both of which are influenced by changes in primary productivity and habitat structure.Widow spider populations suffered greatly in the recent 3-year drought.Winter rains in2000/2001 did not result in an immediate increase in population.We predict that thesespiders will exhibit a population lag of one or more years, similar to that of their main preyspecies. Unlike the widow spiders, the eresid spider responded immediately to increasedprecipitation.The likely reason is that the juveniles of Stegodyphus are protected and fed bythe mother during the period of food shortage and have low mortality during this period.With: O. Eitan

POPULATION PROCESSES

The Mediterranean fruitfly is one of the most destructive pests in Israel and other warmtemperate regions. It attacks many kinds of fruits in all regions of the country, but in thehighlands it is found mainly in the summer. We did not find any support for the traditionaltheory that the fruitfly has permanent populations throughout Israel but that in cold areas,i.e. the central highland region, winter population is very low. We strongly argue that thehighlands are inhabited by a sink population that originates each summer from sourcepopulations in the warm valleys and on the coastal plain.Accordingly, the population in Israelforms one metapopulation with a year-round source and surrounding summer seasonal sinks.If this is true, efforts to eradicate and control the med-fly populations should be altered.With: N.Yisraeli

Parasitic insects are important natural enemies of other insects and play a central role inbiological control. Parasitoid-host interactions are also used as models for exploring thedynamics of predator-prey interactions. I use the parasitic wasp Diaeretiella rapea and its host,the cabbage aphid Brevicoryne brassicae, to explore how foraging decisions affect predator-prey interactions. In the past, I demonstrated how Diaeretiella uses honeydew secreted by theaphid as a mean of 1) finding the aphid on the host plant and 2) making foraging “decisions”as to how many aphids to attack on a plant and how long to stay on it. These studiessuggested that the wasp has adopted a “count-down” process, using honeydew to assess howmany aphids are present in the colony it has encountered.As more aphids are attacked, itstendency to exploit that colony decreases. It is as if the wasp counts down the number ofremaining aphids, while the engaging in his attack of the colony.With: E. Summer

Female black widow spider(Latrodectus revivensis) with her egg

sac.These spiders feed on a widerange of surface-dwelling

arthropods, including scorpions,many times their size.

desertecology 32

POPULATION STRUCTURE

AND THE POTENTIAL FOR

COOPERATION IN A

SUBSOCIAL SPIDER

LUBIN

HABITAT STRUCTURE VERSUS

PRODUCTIVITY AS

DETERMINANTS OF DESERT

COMMUNITY STRUCTURE

AYAL

HABITAT STRUCTURE AND

SPIDER COMMUNITIES

LUBIN

Subsocial spiders exhibit extended maternal care of their offspring, with the young spidersexhibiting a group-living stage inside the mother’s nest before dispersing to establish theirown nests. Social spiders, by contrast, do not disperse, and they remain together during theirentire life cycle, cooperating in nest and web building and in capturing prey.The Negev deserteresid spider Stegodyphus lineatus provides a model of subsocial organization for investigatingthe conditions that may have led to the evolution of permanent sociality. In this species, nestsof siblings are found in distinct neighborhoods that are often widely separated from oneanother. Males that leave their neighborhood to search for females are largely responsible forgene flow between patches. Nonetheless, we still found considerable genetic differentiationdue to the sedentary behavior of females that remain in their natal patch.Although thespiders are annual, individual neighborhoods may persist for several generations, leading toincreased population differentiation. Social interactions among related individuals occurringin dense clusters in the same neighborhood could provide the preconditions for theevolution of permanent social living. Indeed, we found that juvenile spiders distinguishbetween siblings and unrelated individuals even after dispersal: under conditions of foodshortage, siblings were less prone to cannibalize one another than they were to attackunrelated juveniles.With: J. Johannesen, University of Mainz, Germany;T. Bilde-Kofoed,Aarhus University, Denmark

THE STRUCTURE OF DESERT COMMUNITIES

It is commonly believed that the low productivity in deserts results in a simple community inwhich abiotic factors determine organism abundances. However, my studies on tenebrionid(darkling) beetle distribution in the central Negev demonstrated that predation is the keyfactor for understanding habitat segregation among the 20 common species in this area.Predators are either birds, which prefer large tenebrionid species, thereby forcing them intoplant-cover habitats or scorpions, which prefer small species and remove them from habitatswith plant cover.These observations led me to two main hypotheses regarding the factorsthat structure desert communities. Firstly, the habitat segregation of macrodetritivores isbest explained by the existence of two additional trophic levels above them, namely, small(primary) predators mainly scorpions reptiles and large (secondary) predators mainly birdsand small mammals.And secondly, productivity in deserts affects community structure moreas a trait-mediated structural effect then as an energy-trophic effect.The main effect of greaterplant cover in more productive desert habitats is the refuge they provide for large soil-surfacearthropods (e.g., large tenebrionids, scorpions, reptiles, etc.) from large predators (e.g., birds).With: M. Leibold, University of Chicago, Illinois

We examined how the patchy distribution of perennial shrubs in a semi-arid Negev scrublandaffects the species diversity, distribution and abundance of spiders.The spider communityreflects the patchy distribution of shrubs and open ground. Different types of habitat (bareground, large woody shrubs, grass) have spider communities composed of different species.Although the dominant species differed, they played fixed roles in each habitat, i.e., there wasalways one ambush-hunter, one web-builder, one active nocturnal hunter and one diurnalhunter. One shrub, Thymelaea hirsuta, influenced spider communities more than any otherpatch type. Species richness was significantly greater in patches containing this shrub.

desertecology 33

ORGANISMS ACTING AS

ECOSYSTEM ENGINEERS IN

THE NEGEV

SHACHAK

THE DYNAMICS OF PATCH

FORMATION IN SEMI-ARID

SYSTEMS

SHACHAK

THE EFFECTS OF GRAZING ON

PATCHINESS, RESOURCES,

AND ORGANISMS IN A

SEMI-ARID LANDSCAPE

SHACHAK

THE STRUCTURE AND

FUNCTION OF SINK-LIMITED

SYSTEMS

SHACHAK

HUMAN-INDUCED CHANGES

affecting BIOLOGICAL

PRODUCTIVITY AND

DIVERSITY in desertified

landscapes

SHACHAK

THE DECLINE OF THE

MOUNTAIN GAZELLE

(GAZELLA GAZELLA)

POPULATION IN THE GOLAN

HEIGHTS

SALTZ

FUNCTION OF DESERT ECOSYSTEMS

Our studies showed that the productivity and diversity of annual plants in the Negev desertare due to the engineering of the environment by the microphytic soil-crust community,shrubs, porcupines, isopods and snails.With: C. Jones, Institute for Ecosystem Studies (IES), Millbrook, New York

Our results demonstrated that small patch formation, i.e., the formation of soil crust andshrub patches is a combined effect of dust deposition and redistribution of the dust by runoff.Redistribution of the dust creates soil mounds under the shrubs that trap water and seeds.Therefore, most of the productivity and diversity of annual plants is concentrated under theshrubs.With: G Lovett, IES

We found that the effect of grazing in semi-arid landscapes is mainly due to modification ofpatches in the landscape.The grazers decrease the shrub patches by feeding and trampling,and they disturb the crust patches mainly by trampling.The net effect is the decrease ofproductivity in the shrub patches and its increase in the crust patches.With:A. Perevelotsky,Volcani Institute, Bet Dagan, Israel

We found that productivity and diversity of the landscape is lower than what would beexpected from rainfall levels.This is due to the leakage of soil, water and nutrients from thesystem: there are not enough shrub patches capable of acting as sinks for soil, water andnutrients.With: S. Pickett, P. Groffman, IES;A. Karnieli, B. Boeken, E. Zaady, BIDR

Human-made sinks in the landscape, in the form of pits, can decrease the leakage from thesystem. Pits created by man function as sinks, which form water- and nutrient-enrichedpatches providing resources that increase the productivity and diversity of desertifiedlandscapes.With: S. Pickett, IES

CONSERVATION ECOLOGY

The spreading desertification in many areas of the world, including the south of Israel, hasbeen well documented.This phenomenon, along with man-induced disturbances, can lead topopulation extinctions and to the reduction of genetic variation in the populations thatremain. Conservation research in the Mitrani Department concentrated this year on studiesof the impact of human activities on populations of gazelles and on the reintroduction ofendangered mammalian species.

From 1985 to 1993, the gazelle population in the Golan Heights was reduced by hunting from5000 to 2500 animals.This reduction was carried out to prevent foot-and-mouth diseaseoutbreaks.After hunting ceased in 1993, the population continued to decline steadily, and in2000 only 500 individuals were left.We sought to identify the possible causes for this declineand provide management recommendations. Our research showed that the decline isprobably due to low reproductive success due to the predation of jackals on gazelle fawns.Jackal population density is primarily determined by human waste, and it cycles regularly as afunction of rabies outbreaks. In 1993, when almost 30% of the gazelles were removed byhunting, the jackals were entering a fast-growth phase following the last rabies outbreak.Thiscombination of events upset the predator-prey relationship. Because jackals are notdependent on gazelles as their sole source of food, the gazelle decline did not bring about anassociated decline in jackals. Under these conditions, jackals were able to severely curtail thegazelle population. Careful handling of human waste is needed to resolve the problem.

desertecology 34

THE IMPACT OF HUMAN

ACTIVITY ON GAZELLES

ALONG THE SOUTHERN

COASTAL PLAIN OF ISRAEL

AND IBEX IN THE ERETZ

HAMAKHTESHIM REGION

SALTZ

REINTRODUCTIONS: PERSIAN

FALLOW DEER (DAMA

MESOPOTAMICA) AND

ARABIAN ORYX (ORYX

LEUCORYX)

SALTZ

The continued growth of the human population in Israel has brought about increasedpressure by hikers and tourists on previously relatively undisturbed regions.The increasedcontact between man and wildlife in these areas may bring about changes in wildlife behavior,which may ultimately impact their social structure.We evaluated the behavioral responses ofgazelle and ibex to increased human presence. In both species, levels of vigilance increasewith human disturbance, however the response is stronger in the larger groups (suggestingthat small groups are already exhibiting the maximum levels of vigilance possible).Consequently, the advantage of being in larger groups should be reduced and in fact in areaswith greater human disturbance, gazelle groups are smaller.

The high rates of species extinction and loss of biodiversity worldwide has madereintroductions an attractive technique for restoring damaged ecosystems. In Israel, manyspecies have been extirpated by uncontrolled hunting and habitat loss during the Ottomanregime.Two of these species, the Persian fallow deer and the Arabian oryx – both listed bythe World Conservation Union (IUCN) as critically endangered, are currently beingreintroduced in Israel.We are studying the behavior of these species in the wild, investigatingtheir dynamics and habitat preferences and projecting future performance. Results haveshown that both species have adapted to the wild and exhibit “normal” wildlife behaviorpatterns and positive growth rates. Computer models project that by the year 2005 therewill be nearly 250 Persian fallow deer and 100 Arabian oryx in the wild in Israel.

The ibex (Capra ibex nubiana) lives in the mountains of the Negev, the Rift Valley and the Judean desert.

desertecology 35

The Ramon Science CenterDr. Boris Krasnov, Head

The Ramon Science Center conducts long-term research on the ecology and geology of theMakhtesh Ramon and its surrounding environment in the central Negev desert.The Centeris situated in the town of Mizpeh Ramon, about 35 km south of the Jacob Blaustein Institutefor Desert Research in Sede-Boqer and is affiliated with the Mitrani Department of DesertEcology. Makhtesh Ramon is a large erosion crater some 40 km long and about 8 km wide,surrounded by 400 meter-high natural walls. Initially established as a geological park becauseof its remarkable diversity of geological structures and habitats, this crater now forms thecentral part of Israel’s largest nature reserve – the Negev Mountains National Park.MakhteshRamon is home to a wide variety of desert animals and plants, some of which are foundnowhere else. Of particular ecological interest is the fact that the crater forms a naturalboundary between two major biogeographic zones, the steppe (Irano-Turanian) and the true(Sahara-Arabian) desert.As such, the crater is an extraordinary natural laboratory for thestudy of ecological interactions of two floras and faunas.

Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: krasnov@bgumail.bgu.ac.il

Academic STaffAvni,YoavBurdelova, NadezhdaKrasnov, Boris Plakht, Josef Sheinkman,VladimirShenbrot, Georgy

Adjunct Researchers

Dr. Irina KhokhlovaProf. Emanuel Mazor, Weizmann Institute of Science

Satellite photo of Makhtesh Ramon, a large erosion crater in the Negev highlands. Forming a natural boundarybetween the Irano-Turanian steppe region in the north-east and the Sahara-Arabian desert to the south,Makhtesh Ramon presents researchers with unusual opportunities for geological and ecological investigations.

desertecology 36

MONITORING

DESERTIFICATION PROCESSES

IN THE CENTRAL NEGEV

AVNI

MAKHTESHIM area

FAULTS/JOINTS AS

INDICATors of RECENT

TECTONIC ACTIVITY AND

SEISMIC RISK

AVNI

THE MAKHTESHIM REGION

AND DEAD SEA BASIN:

EVOLUTIONARY LINKS

Sheinkman

QUATERNARY

DEVELOPMENT OF THE

MAKHTESHIM OF CENTRAL

NEGEV DESERT

PLAKHT

PISTACIA ATLANTICA AS A

PALEOENVIRONMENTAL

MARKER

AVNI

Research Activities

Geology

The geology of the Makhteshim region continues to pose numerous questions concerning theprocesses contributing to the origins of its unique geomorphology.Additionally,Ramon ScienceCenter geologists are investigating processes of erosion that continue to contribute todesertification of the region.

The study of desertification was initiated in 1984 in Nahal Zipporim and since 1990 has beenexpanded to five other drainage basins in the region. At each site an erosive waterfalldeveloped within the alluvial fill of the valleys.The annual backward migration of the waterfallsis monitored during and after flood events. During 2000, the waterfalls migrated 100-3000 cmin each site, accompanied by a sharp fall in vegetation biomass and by a loss of soil, withimplications for regional agriculture.These processes have led to active desertification of theNegev Highlands, unrelated to any recent climatic change.

During the last years a dense fault system, active during the Quaternary, has been identifiedin the central and southern Negev, within a wide belt of 60-80 km west of the Arava Rift.Theresearch initiated in the year 2000 focused on the geometry and time relation within the jointsystem that accompanies the major fault system.We defined the seismic risk within a wideregion bordered by the Arava rift, which covers the majority of the Makhteshim Country.With: Z. Levi, D. Bahat, Ben-Gurion University

The geomorphological-geological factors affecting the development of wadis running to theDead Sea from the Negev Highlands are studied to estimate erosive-accumulative activity inthe region throughout the Pleistocene and to follow evolutionary links between developmentof Makhteshim region and the Dead Sea basin. Special attention was devoted to the influenceof fluctuations of the Dead Sea and its precursors on the development of wadis by formingestuaries within them. The development of terrace staircases is a good indicator fordetermining the course of geological events in the wadis. Dating of Quaternary sedimentaryallowed us to reconstruct the development of the valleys during the Late Pleistocene.

Climatic fluctuations during the Pleistocene were the main factor that determined the similarmorphostratigraphy of fluvial terraces and pediments in the Makhteshim. It is suggested thatin a sensitive desert region even minor fluctuations within climatic phases (both pluvial andinterpluvial) can induce major changes in the reaction of the fluvial systems.

Ecology

Ecological research focuses on certain key groups of organisms. Indigenous pistachio treestell us about the early climate of the region.The distribution and abundance of snails anddesert rodents provide insights into behavioral, physiological and ecological adaptations tohyper-arid habitats. And new research on the ecology of ectoparasites can clarify therelationships between fleas, which are carriers of various diseases, and their rodent hosts.

In the Negev highlands, several hundred large trees of Pistacia atlantica, some of themestimated to be more than 800 years old, are key members of the desert ecosystem.Thestudy focused on environmental aspects that included the geologic structure of the substrate,the position and location of the trees within the geomorphological system, soil moisturecontent, and the influence of the flood regime on the Pistacia population.These ancient treesprovide a way of assessing geomorphological, environmental and climatic changes thatoccurred in the desert ecosystem of the region.

desertecology 37

EFFECT OF HOST DENSITY ON

ECTOPARASITE

DISTRIBUTION

KRASNOV

EFFECTs OF AIR TEM-

PERATURE AND HUMIDITY

ON SURVIVAL OF PRE-

IMAGINAL STAGES OF TWO

FLEA SPECIES

KRASNOV, BURDELOVA

BEHAVIORAL CORRELATES OF

SPATIAL DISTRIBUTION IN

THE RODENT GERBILLUS

DASYURUS

KRASNOV, SHENBROT

Rodent and snail

biodiversity in different

habitats of the southern

Israel

Shenbrot, Krasnov

ECOLOGY OF ECTOPARASITES AND THEIR RODENT HOSTS

The pattern of parasitism of the flea species Xenopsylla dipodilli and Nosopsyllus iranus theodorion the desert rodent Gerbillus dasyurus was studied as a function of host density. As hostdensity increased, the flea infestation increased in either curvilinear fashion to an asymptote(for X. dipodilli), or linearly (for N. i. theodori).The prevalence of infestation changes eitherunimodally (X. dipodilli) or logarithmically (N. i. theodori) as host density increases. In addition,there is a positive relationship between the mean number of fleas per host and thepercentage of hosts infested. Simulations of the fraction of resident hosts demonstrates thatthis latter parameter influences the relationship between host density and flea burden onlywhen residents comprise no more than 50% of all host individuals.

Development and survival of fleas is highly dependent on environmental conditions(temperature and humidity). However, this has never been tested on most of the flea speciesthat parasitize wild rodents. In addition, it is not known which environmental conditions andphysical parameters are critical for the survival of flea species in particular habitats.Weinvestigated the effect of the habitat of host species (rodents) on their ectoparasites (fleas)in the Ramon erosion cirque.We found that the replacement of one species of flea,Xenopsyllaconformis, with a second flea, Xenopsylla ramesis, occurred on the rodent Meriones crassuspopulating two different habitats situated at the opposite sides of a steep precipitationgradient.We tested the hypothesis that air temperature and humidity are important in thestructuring of host-ectoparasite relationships affecting the survival of the pre-imaginal stagesof the fleas. Survival of X. conformis eggs did not depend on either temperature or humidityor both, whereas eggs of X. ramesis had significantly poorer survival at lower than at higherhumidity. No larva of either species survived at lower humidity, independent of temperature.Pupal survival was higher at higher humidity, independent of temperature. Survival of X.conformis pupae was lower than that of X. ramesis pupae when humidity was low.With: I. Khokhlova

PATTERNS OF SPECIES DIVERSITY AND ABUNDANCE

The spatial organization of Gerbillus dasyurus is characterized by isolated aggregations ofseveral individuals within a homogeneous habitat.We studied the behavioral interactionsbetween individuals from the same and from different aggregations in male-male and female-female paired encounters in an arena.We tested the hypothesis that individuals show moreaggressive behavior upon detecting strangers than when sensing neighbors.The number ofcohesive (nonaggressive) interactions between gerbils was much higher than that ofaggressive behaviors. Male opponents in neighbor pairs demonstrated both aggressive andcohesive interactions significantly less frequently than opponents in nonneighbor pairs.Therewere no differences in behavior between neighbor and nonneighbor pairs of females. Maleencounters were more asymmetrical than female encounters in terms of defensive behavior,but not in terms of offensive behavior. Moreover, in male encounters, the defensiveasymmetry was significantly higher than offensive asymmetry.These data clarify the pattern ofspatial distribution of individuals from the pattern of their behavioral interactions.With:V. Gromov, Institute of Ecology and Evolution, Moscow

This project was devoted to development of an Intelligent Biodiversity Information Systemfor the central Negev The system will allow decision makers to identify patterns ofbiodiversity at spatial scales ranging from local sites of 100x100 m2 to the entire centralNegev, and to evaluate local and regional losses in biodiversity expected from potentialscenarios of habitat destruction and development programs. Developed components of thesystem include empirically derived species-response models that predict probabilities ofspecies occurrences (land snails) or abundances (rodents) at a site from information onclimate, soil, relief and vegetation. Data for model calibration were obtained from extensivesampling of the main environmental gradients of the central Negev (the faunal data onrodents and snails), maps available in a digital form (rainfall, temperature, topography, soils)

desertecology 38

LONG-TERM POPULATION

AND COMMUNITY

DYNAMICS OF RODENTS IN

THE CENTRAL NEGEV

SHENBROT

METABOLIC RATE AND

RESPIRATORY GAS-

EXCHANGE PATTERNS IN

DARKLING (TENEBRIONID)

BEETLES

KRASNOV

ARCHITECTURE AND MICRO-

CLIMATE OF RODENT

BURROWS (MERIONES

CRASSUS)

SHENBROT, KRASNOV

and satellite images (vegetation). Iindividual species models were combined to estimate localvariation in species richness and diversity. Focal areas with maximal species diversity weredetermined as most important for conservation demands.With: R. Kadmon,Y. Heller, Hebrew University of Jerusalem;Y.Yom-Tov,Tel Aviv University

The monitoring of rodent populations began in 1993 on 24 sample grids established inMakhtesh Ramon and its vicinity.This long-term program aims at assessing the influence ofenvironmental fluctuations on populations of individual species, as well as on the communityas a whole. Among habitat specialist species, Gerbillus gerbillus, Mus musculus and Acomyscahirinus, there was a high correlation between current density and the amount of rainfall inthe previous rainy season. Specialist Sekeetamys calurus has a low and stable density that didnot show any relation to rainfall.Among habitat generalists, densities of two species, Gerbillusdasyurus and Psammomys obesus, were correlated with the amount of rainfall in the previousrainy season.Two other species, Jaculus jaculus and Acomys russatus, did not show any relationto rainfall patterns in any of the occupied habitats.The most complicated patterns occurredin the two last generalist species, Gerbillus henleyi and Meriones crassus.Their densities werecorrelated with rainfall in some of the occupied habitat types, but not in others. Densities inother habitats were determined by densities in adjacent habitats and of competing species.

ACTIVITY CYCLES AND MICROCLIMATE

This study correlates the pattern of external gas exchange with the timing of activity of ninespecies of tenebrionid beetles of the Negev desert.The study species are active throughoutthe summer months when daytime temperatures are high and rain is absent.There was nodifference in the standard metabolic rate of the nine species, determined by flow-throughrespirometry.All the nocturnally active beetles exhibited a form of continuous respirationwhereas the three diurnally active species exhibited a cyclic form of respiration, known as adiscontinuous gas-exchange cycle (DGC).The DGCs recorded have a long flutter periodconsisting of miniature ventilations, during which a total of 29-48% of total CO2 output tookplace.The flutter period played an important role in the modulation of metabolic rate incontrast to studies on other arthropods, in which the burst period was found important.Wesuggest that the long flutter period is important for reducing respiratory water loss in ariddwelling arthropods.The results support the hypothesis that DGC helps reduce respiratorywater loss in beetles and minimizes the risk of desiccation.With: F. Duncan, University of the Witwatersrand, South Africa

Burrows of Meriones crassus were studied in two habitats in the central Negev desert.Burrows in the loess habitat were more complex than in the sand habitat.To measure theburrow microclimate, artificial burrows were constructed in natural habitats and equippedwith temperature and relative humidity data loggers. Daily fluctuations of temperature andrelative humidity in burrows were much lower than those of ambient air. Average burrowtemperatures were higher than air temperatures. The difference between average dailyambient and burrow temperatures was higher in the sand habitat than in the loess habitat.Average relative humidity in the burrow of the sand habitat was lower than that of ambientair throughout the year, while in the loess habitat it was lower only during the summer andautumn. In winter and spring, relative humidity of loess burrow air was significantly higherthan that of ambient air.The presence of nest material in the burrow chamber increasedrelative humidity. Laboratory experiments demonstrated that an animal’s presence in theburrow chamber increased soil water content at the chamber floor, an effect that persistedfor at least two months after removal of the burrow inhabitants.

desertecology 39

BIODIVERSITY OF INSECTS IN

A CHANGING AND

DEVELOPING DESERT

ENVIRONMENT

YAROM

HAZEVA RESEARCH ANDDEVELOPMENT CENTER (HRDC)

Dr. Ilan Yarom, Scientific Director

The Hazeva Research and Development Center (HRDC) is located in the central Arava RiftValley, between the Dead Sea and Elate.The Arava Rift Valley, home to some of the mostpristine habitats in Israel, offers singular opportunities for research.There is an extraordinaryconfluence of natural ecosystems in the area with a beautiful and fragile mixture of plants andanimals originating from different biogeographical zones: African acacia trees, the Arabianbabbler (an Asian songbird), and the common wolf whose habitat extends to Europe. Manyspecies cannot be found elsewhere in Israel.The nearby Shezaf Nature Reserve has an areaof about 9,500 acres and serves as a natural laboratory for scientific research.

The Ministry of Science, Culture and Sport and the Central Arava Regional Council are themain sponsors of HRDC, and since 1996 HRDC has been academically affiliated with Ben-Gurion University’s Jacob Blaustein Institute for Desert Research.

The major areas of research at HRDC are: biodiversity, conservation of natural resources,ecological tourism, sustainable agriculture and regional development. Researchers fromacademic institutions in Israel and around the world collaborate on research activities.

Hazeva Research and Development Centerc/o Hazeva Field School, Mobile Post Office Ha’Arava 86815, Israel

Phone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: iyarom@bgumail.bgu.ac.il

Research StaffDr. Ilan Yarom, Entomologist Dr. Rivka Ofir, Cell biologist and molecular geneticist Dr.Vasiliy Kravchenko, Entomologist, Research FellowDr.Avner Anava, Zoologist; Postdoctoral FellowGideon Wasserberg, Ph.D. candidate (Ben-Gurion University)

Technical/support staffDr.Vasiliy Kravchenko, EntomologistMrs. Edna Nave - Technical supportMrs. Marjatta Gotfeled - Office specialist

Research Activities

Ecosystems in the Arava valley

Because insect fauna of the Arava rift valley is poorly known, we have initiated the firstcomprehensive,multiyear study of insect diversity of this ecosystem.Special attention is beinggiven to identifying potential crop pests, on the one hand, and promising natural enemies, onthe other,which may serve as biological agents in future biological control or integrated-pest-management in regional agriculture. Insects are collected throughout the year by staffmembers, as well as by visiting entomologists, using various methods, including aerialcollecting, Malaise traps, light traps, etc.The material is preserved by the regular methods andidentified by local taxonomists and colleagues around the world. Most of the material,including type specimens of the new species, is deposited at the National Collection ofInsects at the Department of Zoology,Tel Aviv University.With:V. Kravchenko

desertecology 40

BIODIVERSITY OF TAMARIX

AND ASSOCIATED INSECTS IN

various HABITATS

YAROM

ECOLOGY OF FRESH-WATER

RESERVOIRS IN THE ARAVA:

LIMNOLOGIC AND ECOLOGIC

EFFECTS IN THE RESERVOIRS

AND DOWN-STREAM

YAROM

IMPACT OF FLASH-FLOOD

INTERCEPTION ON SHALLOW

ARAVA GROUNDWATER:

interrelationship IN

NATURAL AND DISTURBED

SYSTEMS

YAROM

ARAVA REGIONAL

DEVELOPMENT and

RELATIONSHIPS BETWEEN

RESERVOIR HOST AND

VECTOR OF CUTANEOUS

LEISHMANIASIS

YAROM

THE FAT SAND RAT

(PSAMMOMYS OBESUS) AS A

POTENTIAL TOURIST

ATTRACTION FOR THE

ARAVA

ANAVA

PHYTOCHEMICALS IN ARAVA

PLANTS: SCREENING FOR

PHARMACEUTICAL activity

OFIR

The unique ecosystem comprising species of Tamarix and their associated insects was studiedin natural and disturbed habitats. Habitats in the Arava were also compared with those in thecoastal plain and Dead Sea areas.With: D. Gerling,A. Freidberg,A. Eshel,Tel Aviv University; C. Zebitz, University of Hohenheim, Stuttgart, Germany.

A new system of water reservoirs was built in recent years in Wadi Arava. They weredesigned to capture desert floodwaters for irrigation and to support the undergroundaquifers. In this study we 1) identified the dynamics of the limnological processes of thecaptured water and 2) identified the ecological process influenced by the reservoirs, bothabetting the reservoirs and down stream. Preliminary results show remarkable differencesbetween the two reservoirs under investigation: The downstream reservoir (“Idanreservoir”) is more eutrophic than the reservoir upstream (“Zukim reservoir”).We suspectthat the intensive agriculture, taking place between the two reservoirs in Wadi Arava, butabsent upstream from the Zukim reservoir, contribute to accumulation of nutrients in Idanreservoir.We found rapid microalgal growth in the Idan reservoir as compeard to that in Zukim.With: S. Gafny,Tel Aviv University.

We are clarifying the relationships between flash-flood water and shallow groundwater andexamining the impact of a massive environmental disturbance (namely, the catching offloodwater) on the natural balance of the Arava water system. The study involvesgeochemical and isotopic characterization of shallow groundwater near water reservoirs,their temporal and spatial changes, and the development of a model for evaluating therelationships between floodwater, captured water and groundwater.With:A. Bein,A. Burg, Geological Survey of Israel

Cutaneous leishmaniasis (“Jericho-rose lesion”) is a common human disease in the Aravavalley caused by a parasite transmitted from local rodents to humans by sand flies.Althoughcutaneous leishmaniasis is not a lethal disease, the lesion may leave a noticeable scar.Westudy the major environmental factors that affect carrier rodent populations, such aspopulation dynamics and ecology, patterns of dispersal and activity, and epidemiology of therodent population, as well as the influence of human activity on rodent and sand fly (thevector) populations.With: G.Wasserberg, Z.Abramsky, Ben-Gurion University;A.Warburg, Hebrew University of Jerusalem.

Research and development projects

The fat sand rat is a diurnal rodent that lives in small aggregations.The goal of this study is todevelop a new attraction for ecological tourism.This attraction will be in addition to theArabian babbler, which is a well-known, indigenous, social bird that attracts students fromIsrael and abroad.The researchers are working in two directions: 1) accustoming the gerbilsto the presence of human observers; and 2) studying the behavior of the gerbils, theirphysiology and other matters that will provide the basis for an ecotourism program.With: M. Kam,A. Degen, BIDR

The study of phytochemicals involves four projects, which may be developed into futurebiotechnology enterprises:a) We are developing a collection of desert plant extracts, which will serve as a library ofnatural products for screening for phytochemicals that may function against various biologicaltargets relevant to human disease.b)High throughput screening (HTS) is being used to identify plants containing phytochemicalsthat activate or repress the “killing proteases” (caspases) involved in programmed cell death(apoptosis). HTS of the first 100 desert plant extracts resulted in the identification of 10 plants

desertecology 41

MICROBIAL DEGRADATION

OF POLYETHYLENE WASTE IN

THE ARAVA VALLEY

OFIR

containing phytochemicals capable of activating caspase-3 activity in cancer cells, leading tocytotoxicity accompanied by DNA ladder.c)HTS of natural products is underway to identify materials repressing serotonin re-uptake,potential drugs for treating depression in pre- and postmenopausal women. Serotonin playsa major role in depression at times of changing hormones levels in women. Phytochemicalswill be screened for their effect on the uptake of serotonin by recombinant human-serotonintransporter.d)HTS of Indian plant extracts are being applied to detect cytotoxic activity against cancercells and for pro-apoptotic activity.Thirty extracts prepared from Indian plants used by localIndian doctors as medicines were screened for pro-apoptotic activity.Two plants containcompounds capable of activating caspase-3 and killing human cancer cells grown in vitro.Plants with functional activity may be considered for future cultivation as a potential newcrop in the Arava.

The use of isolated bacteria that can use polyethylene as their sole source of carbon is testedin a pilot project in the Arava.The research aims at developing a biotechnological method forusing these bacteria for degrading the large mounds of polyethylene waste accumulatedduring agricultural use.With:A. Sivan, Institute for Applied Research, Ben-Gurion University

Polyethylene greenhouses are used extensively in the Arava valley, where out-of-season and exotic producemarketed abroad are important sources of income.

desertecology 42

THE ROLE OF MICROPHYTIC

SOIL-CRUST COMMUNITIES IN

THE NEGEV DESERT

ZAADY

CONTRIBUTION OF

DEPOSITED AEOLIAN

ORGANIC MATTER TO A

DRYLAND ECOSYSTEM

ZAADY

Desertification and RestorationEcology Research Center

Dr. Eli Zaady, Resident Scientist

The DRERC promotes research into the causes of desertification and develops means ofpreventing desertification and of restoring already desertified areas. Establishment of theDRERC in BIDR was at the initiative of the Jewish National Fund (JNF) which neededresearch support for their dryland development projects.The JNF Savannization Project isone of the major activities of the DRERC.This project includes studying the relationshipsamong landscape mosaic, resources and organisms and the source-sink relationships amonglandscape units that contribute to the diversity and productivity of drylands. In desertifiedareas, the relationships are such that water, soil and nutrients leak from the system,decreasing productivity and diversity.We have adopted a management approach for retentionof resources and harvesting runoff water in order to increase productivity.The methodologyfocuses on creating human-made patches that are relatively rich in water; it involves atechnique utilizing runoff water harvesting and storage.

Research Activities

Soil-crust communities and nutrient cycling

A central assumption of the Savannization Project is that plant and animal production anddiversity in arid regions depend on the distribution and abundance of soil microphytic crusts.This relationship is due to the function of the microphytic soil crust as a major source andcontroller of water and nutrients for higher plants.We examined the processes of recoveryof the microphytic soil crust following a variety of disturbances, which included theconstruction of pits and mounds, scraping of the soil surface and the application of herbicides.We found that soil-crust recovery in the Negev takes about seven to ten years. During thistime, soil infiltration and soil erosion decreases and moss density increases. Since naturalrecovery of soil crusts are not very long processes, we recommend that for a few years aftera heavy disturbance, managers should prevent human activities and grazing in order tofoment crust-cover restoration.This is of importance because biologic productivity anddiversity in the Negev is concentrated mainly in the shrub patches. Since shrub patchesdepend on soil-crust patches for their supply of resources, recovery of the soil crust bringswith it an increase in productivity and diversity of the landscape as a whole.

Three dominant components were found in deposited aeolian organic matter: plant material,insect residues and snail residues (feces).A five-year study of the accumulation of wind-borneorganic matter exhibited significant spatial and temporal differences. For example, there weresignificant differences in the average annual accumulation of organic matter over the fiveyears under investigation.The results showed that the origin of most of the organic mattercontent was from native sources.The highest and most significant amount was registeredduring the spring, when flowering takes place in the northern Negev.This may explain thelarge quantity of plant material and insect and snail residue (feces) that were also foundduring this season. Since the crust patches serve as a source of water and nutrients in thisecosystem, the organic residues that are of high nutrient quality and readily decomposablecontribute to the productivity of the shrub patches and thus of the overall ecosystem.

The Microphytic soil crust in theNegev highlands near Sede-Boqer(100 mm average annual rainfall).

desertecology 43

RELEASE AND CONSUMPTION

OF NITROGEN BY SNAIL FECES

IN NEGEV DESERT SOILS

ZAADY, SHACHAK

NITROGEN FIXATION IN

MACRO- AND MICROPHYTIC

PATCHES IN THE NEGEV

ZAADY, SHACHAK

SOIL FROM MICRO- AND

MACROPHYTIC PATCHES AS

REGULATORs OF NITROGEN

AND CARBON DYNAMICS

ALONG RAINFALL GRADIENT

ZAADY, SHACHAK

LITTER: A REGULATOR OF

NITROGEN DYNAMICS IN

MACROPHYTIC PATCHES

ZAADY, SHACHAK

EFFECT OF HERBICIDES ON

FLOW OF WATER, SOIL AND

NUTRIENTS in the desert

ecosystem

ZAADY, SHACHAK

GERMINATION OF

MUCILAGINOUS SEEDS ON

CYANOBACTERIAL SOIL

CRUST

ZAADY

We sought to characterize the nature and amount of potential nitrogen release from a) fecesof two different species of snails, b) the feces of the same species of snail when fed differentplants, and c) to make preliminary evaluations of the importance of N release from feces inthe context of the N budget of the Negev desert.All feces types released significant amountsof N following wetting of dry soil. Rainfall events create pulses of water and N availability thatare likely critical for plant growth. Nitrogen release from snail feces may play an importantrole in the N cycle in the Negev desert.With: P. Groffman, Institute for Ecosystem Studies (IES), Millbrook, New York

We tested the hypothesis that nitrogen-fixation within macrophytic patches is a lessimportant source of N in Negev desert ecosystems and landscapes than the N-fixationpotential of microphytic crust and macrophytic patch soil/litter types. Free-living N-fixingbacteria are important when desert patchiness is taken into consideration.Higher rates of N-fixation were observed in soil from macrophytic patches than in soil-crust material.Thegenerally high carbon content of the macrophytic patch soil/litter and the particularly high C-to-N ratio of the largest size class of this material appears to facilitate N fixation inmacrophytic patches desert.With: P. Groffman, IES

We quantified available nitrogen production within micro- and macrophytic patches followingrewetting events in order to evaluate whether microbial immobilization and denitrificationcan compete with plants for this N and to determine the effect of the rainfall gradient onnutrient cycling in the desert. Preliminary results show that differing precipitation levels havesignificant effects on nutrient cycling in desert soils.With: P. Groffman, IES

Litter plays a major role in conserving nitrogen following wetting events in Negev soils.Amounts of NH4

+ and NO3_

in soil and of N in microbial biomass were reduced intreatments that augmented litter, suggesting that significant quantities of N were sequesteredin litter, especially the largest size classes of litter particles.The immobilization and release ofN by litter may be especially important in the N cycle in desert ecosystems.With: P. Groffman, IES

Herbicide spraying disturbs the microphytic soil crust and thereby alters the functioning ofthe desert ecological system.The destruction of weeds did not significantly increase runoff,but it did damage the microphytic community, resulting in an increased loss of soil and organicmatter.Therefore, the use of herbicides in open areas that are covered with microphytic crustis not recommended. It can be used for purpose of annual removal and increasing infiltrationin small areas like under trees.

Germination and seedling ecology

Although various species have mucilaginous seeds, the mucilage alone does not engender theability (or advantage) to grow on a cyanobacterial soil crust. Each species has developed adifferent strategy – be it biological and/or structural – in their growth response tomicrophytic soil crusts in the ecosystem.With: B. Boeken,Y. Guttermann, BIDR

desertecology 44

GERMINATION OF

PLANTAGO CORONOPU ON

MICROPHYTIC SOIL CRUST

ALONG the RAINFALL

GRADIENT

ZAADY

EFFECT OF MICROPHYTES ON

SPECTRAL REFLECTANCE OF

VEGETATION IN SEMI-ARID

REGIONS

ZAADY

WATER INFILTRATION

THROUGH THREE

CONTRASTING BIOLOGICAL

SOIL CRUSTS IN PATTERNED

LANDSCAPES

ZAADY

PATTERNS OF CO2 EXCHANGE

IN BIOLOGICAL SOIL CRUSTS

OF SUCCESSIONAL AGE

ZAADY

The different microphytic soil crusts occurring along the rainfall gradient in the desertaffected the germination of Plantago coronopus seeds.As the rainfall decreases, the percent ofseed emergence was significantly increased.The soil crust caused a delay and decrease (ca.50%) in seed germination as compared to a control (filter paper Whatman No.1, with doubledistilled water).With:Y. Guttermann, BIDR

Ecosystem patterns

Ecological and hydrological knowledge are being applied to developing managementprinciples and techniques for increasing biotic productivity of drylands while conservingbiodiversity. We discuss the structure and function of the man-made savanna and its potentialas a green belt and rangeland for benefiting human society.

We investigated the hypothesis that the high reflectance of vegetation in semi-arid regions iscaused by the photosynthetic activity of lower plants, which in the absence of higher plantscover most of the rock and soil surface in these regions. We found that in semiaridenvironments, the reflectance of lower plant communities may lead to misinterpretation ofthe vegetation dynamics and the overestimation of ecosystem productivity.With:A. Karnieli, BIDR

Removal of a thin cyanobacterial-dominant crust from a sandy dune at Nizzana in the central-western Negev, as well as removal of a well-developed lichen-dominant and cyanobacterial-dominant crusts from a loess-covered hillside at Sayeret Shaked (LTER) in the northernNegev, resulted in a three- to five-fold increase in absorptivity and steady-state infiltration.We maintain that removal of the crusts in all three landscapes would influence resourceflows, particularly with respect to the redistribution of runoff water.This would also havemarked negative effects on germination and the establishment and survival of vascular plantsand soil biota, leading ultimately to desertification.

Rates of net photosynthesis and respiration obtained using the two different enclosures aswell as two different experimental approaches (long- and short-cuvette adaptation) werefound to be comparable.We found a substantial gradient of CO2 exchange at the Nizzana sitefor both respiration and photosynthesis.The data sets obtained in the course of this studyshow substantial net assimilation rates of CO2, which are in a range similar to darkrespiration rates. The soil-crust samples of the Negev desert show comparable values.Hence, as ecotypes containing such biological soil crusts with dominant photosyntheticallyactive organisms are a widespread phenomenon in desert, boreal and arctic systems, theircontribution to the global cycling of trace gases and elements can be significant for globalbudgets.

desertecology 45

Zvika Abramsky

Yoav Avni

Yoram Ayal

Amos Bouskila

Nadezhda Burdelova

Burt P. Kotler

Boris Krasnov

Yael D. Lubin

Ariel Novoplansky

Rivka Ofir

Research Interests

Ph.D. Colorado State University, 1976; ProfessorIncumbent of The Abraham and Bessie Zacks Chair in Desert EcologyCommunity ecology of desert rodents: Applying the theory of density-dependent habitatselection to measure the magnitude and energetic costs of biotic interactions (competitionwithin and between species and predator-prey interactions).Phone: 972-8-646-1342 • Fax: 972-8-647-2890 • E-mail: zvika@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1998; Researcher Grade CGeology: Morphotectonics; Erosion processes; Palaeogeographic reconstructions.Phone: 972-8-658-8754 • FAX: 972-8-658-6369 • E-mail: avni@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1978; Senior Researcher Community ecology in relation to primary productivity; Desert community structure;Dynamics of parasitoid-host interactions from the individual to the population; Dynamics ofinsect-plant interactions.Phone: 972-8-659-6774 • Fax: 972-8-659-6772 • E-mail: ayal@bgumail.bgu.ac.il

Ph.D. University of California at Davis, 1993; Senior LecturerBehavioral and community ecology; Behaviors related to predation; Conservation of reptilespecies and habitats; Mathematical models for behavioral studies.Phone: 972-8-659-6775/646-1278 • Fax: 972-8-659-6772 • E-mail: bouskila@bgumail.bgu.ac.il

M.Sc. Kazakh State University, 1976; Research AssociateParasitology: Flea-rodent relationships.Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: nadburd@bgumail.bgu.ac.il

Ph.D. University of Arizona, 1983; ProfessorCommunity, evolutionary, and behavioral ecology; Optimal foraging and habitat use;Trade-offbetween food and safety, implications of information available to foragers; Foraging gamesbetween predators and their prey; Mechanisms of coexistence among desert seed-eating birdsand mammals; Applying foraging theory and mechanisms of species coexistence toconservation.Phone: 972-8-659-6785 • Fax: 972-8-659-6772 • E-mail: kotler@bgumail.bgu.ac.il

Ph.D. Moscow State University, 1986; Senior ResearcherAnimal ecology: Population and community ecology of small mammals; Animal behavior;Community ecology of ground-dwelling arthropods; Host-ectoparasite relationships.Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: krasnov@bgumail.bgu.ac.il

Ph.D. University of Florida, 1972; ProfessorBehavioral and evolutionary ecology of arachnids, particularly spiders: Behavioral adaptations todesert conditions; Mating strategies; Maternal care of young; Social behavior; Dispersal andpopulation structure; Influence of habitat structure on spider species diversity.Phone: 972-8-659-6782 • Fax: 972-8-659-6772 • E-mail: lubin@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1990; Senior LecturerEvolutionary ecology of plants; Plant morphogenesis; Phenotypic plasticity of plants; Life-historytactics and strategies of plants; Information perception and processing by plants; Genetics ofdrought-responsive genes; Improving plant response to CO2 fertilization; Ecologicalimplications of the wind dispersal of pine seeds.Phone: 972-8-659-6820 • Fax: 972-8-659-6821 • E-mail: anovopla@bgumail.bgu.ac.il

Ph.D. Ben-Gurion Universiy of the Negev, 1985; Researcher Grade CMolecular biology; Cell biology; Phytochemicals; SIgnal transduction; Normal and cancer cells;Immunology.Phone: 972-8-659-6773 • Fax: 972-8-658-2068 • E-mail: rivir@bgumail.bgu.ac.il

desertecology 46

Berry Pinshow

Josef Plakht

Uriel N. Safriel

David Saltz

Moshe Shachak

Georgy Shenbrot

Vladimir Sheinkman

David WarD

Ilan Yarom

Eli ZaadY

Yaron Ziv

Ph.D. Duke University, 1975; ProfessorPhysiological ecology; Energy and water exchange between animals and the environment;Thermoregulation and osmoregulation in desert animals; Avian respiration, thermoregulationand osmoregulation, and their role in flight duration of migrating birds; Biogeography of birds inthe Negev; Body composition in migrating passerines; Blood-gas transport.Phone: 972-8-659-6773 • Fax: 972-8-659-6772 • E-mail: pinshow@bgumail.bgu.ac..il

Ph.D. Moscow State University, 1978; Researcher Grade BGeomorphology: Geomorphological and Quaternary mapping; Stratigraphy and palaeogeography.Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: josefp@bgumail.bgu.ac.il

Ph.D. Oxford University, 1967; ProfessorAvian ecology; Conservation ecology; Ecology of desertification and climatic change, effects on foragegrasses and the Chukar partridge; Ecological implications of the wind dispersal of pine seeds.Phone: 972-8-659-6700 • Fax: 972-8-659-6703 • E-mail: urielsf@bgumail.bgu.ac.il

Ph.D. Colorado State University, 1988; Senior LecturerWildlife management and conservation biology; Wildlife population dynamics, includingungulate ecology; Mountain gazelles and harvesting; Ecology of small populations;Reintroduction of Arabian oryx and Persian fallow deer; Space-use patterns of wolves in theGolan; Human impact on wildlife; Ecology of ibex populations.Phone: 972-8-659-6778 • Fax: 972-8-659-6772 • E-mail: dzaltz@bgumail.bgu.ac.il

Ph.D. Hebrew University of Jerusalem, 1976;Associate ProfessorWatershed ecology of arid lands; Ecology of desertification; Ecological management; Ecologicalsystems; Role of animals in the functioning of arid ecological systems.Phone: 972-8-659-6786 • Fax: 972-8-659-6772 • E-mail: shachak@bgumail.bgu.ac.il

Ph.D. Moscow State University, 1980; Researcher Grade AZoology: Community ecology of desert animals; Protection of endangered and rare species.Phone: 972-8-658-8764 • FAX: 972-8-658-6369 • E-mail: shenbrot@bgumail.bgu.ac.il

Ph.D. Institute of Geography of the Russian Academy of Sciences, 1981; Research Associate Geography: Quaternary geology and geomorphology.Phone: 972-8-658-8764 • Fax: 972-8-658-6369 • E-mail: sheinkma@bgumail.bgu.ac.il

Ph.D. University of Natal, 1987;Associate ProfessorCo-evolution of plant-herbivore systems; Defensive and growth responses of plants toherbivores; Relative effects of mammalian and insect herbivores on plant communities;Conservation of multispecies herbivory systems and endangered plants.Phone: 972-8-659-6781 • Fax: 972-8-659-6772 • E-mail: ward@bgumail.bgu.ac.il

Ph.D. University of Kansas, 1995; Researcher Grade CEntomology; Biodiversity; Systematics and taxonomy of flies; Biology, ecology and control ofagricultural pests; Desert ecology; Environmental impact of modern settlement on drylands.Phone: 972-8-658-1641 • Fax: 972-8-658-2068 • E-mail: iyarom@bgumail.bgu.ac.

Ph.D. Hebrew University of Jerusalem, 1992; Researcher Grade CNutrient flows in dryland ecosystems; Soil desertification and restoration; Rhizosphereecology; Soil microbiology and microbial ecology; Landscape and microphyte ecology.Phone: 972-8-659-6784 • Fax: 972-8-659-6772 • E-mail: zaady@bgumail.bgu.ac.il

Ph.D. University of Arizona, 1998; LecturerPopulation Ecology: Species interactions and coexistence; Habitat selection; Foraging behavior.Community ecology: Patterns of species; Diversity and community structure; Role of habitatdistribution and arrangement in community organization; Species-area relationships. Landscapeecology: Effects of environment on community organization. Conservation biology: Use of landscape-scale modeling for providing management policies for nature reserves and endangered species.Phone: 972-8-646-1373 • Fax: 972-8-647-2890 • E-mail: yziv@bgumail.bgu.ac.il

desertecology 47

Publications

Abramsky, Z., M.L. Rosenzweig and A. Subach.The energetic cost of competition: Gerbils as moneychangers. Evolutionary Ecology Research 2:279-292(2000)

Amir, N., M.E.Whitehouse and Y. Lubin. Food consumption and competition in a communally feeding social spider, Stegodyphus dumicola (Eresidae).Journal of Arachnology, 28:195-200 (2000)

Avni,Y.,Y. Bartov, Z. Garfunkel and H. Ginat.The evolution of the Paran drainage basin and its relation to the Plio-Pleistocene history of the AravaRift western margin, Israel. Israel Journal of Earth Science 49:215-238 (2000)

Avni,Y.,Y. Bartov, Z. Garfunkel and H. Ginat.The Arava Formation: A Pliocene – Early Pleistocene formation from the Arava Valley and its westernmargin, southern Israel. G.S.I. Current Research 12:221-230 (2000)

Ayal,Y. The role of habitat productivity and plant structure in the determination of herbivore size and the number of trophic levels in terrestrialcommunities. Bulletin of the Ecological Society of America 81:47 (2000)

Crouch,T. and Y. Lubin. Effects of climate and prey availability on foraging in the social spider Stegodyphus mimosarum (Araneae, Eresidae). Journal ofArachnology 28:158-168 (2000)

Eldridge, D.J., E. Zaady and M. Shachak. Infiltration through three contrasting biological soil crusts in patterned landscapes in the Negev, Israel.Catena 40:323-336 (2000)

Fierer, N.G. and B.P. Kotler. Patch discrimination in gerbils: Evidence for micropatch selection and the effects of distinct and vague boundaries. Journalof Functional Ecology 14:176-182 (2000)

Fisher, J.T., M. Stafford-Smith, R. Cavazos, H. Manzanilla, P.F. Folliott, D. Saltz, M. Irwin,T.W. Sammis, D. Swietlik, I. Moshe and M. Sachs. Land use. In: AridLands Management – Towards Ecological Sustainability (Eds. T.W. Hoekstra and M. Shachak), University of Illinois Press, Urbana, pp.143-170 (1999)

Garb, J., B.P. Kotler and J.S. Brown. Consequences of seed size in foraging and species interactions among Negev Desert granivores. Oikos 88:291-300 (1999)Ginat, H., E. Zilberman and Y. Avni. Tectonic and paleogeographic significance of the Edom River, a Pliocene stream that crossed the Dead Sea Rift

valley. Israel Journal of Earth Science 49:159-178 (2000) Gromov,V., B. Krasnov and G. Shenbrot. Space use in Wagner’s gerbil Gerbillus dasyurus (Wagner, 1842) in the Negev Highlands, Israel. Acta

Theriologica 45:175-182 (2000)Karasov,W.H. and B. Pinshow. Test for physiological limitation to nutrient assimilation in a long-distance passerine migrant at a springtime stopover

site. Physiological and Biochemical Zoology 73:335-343 (2000)Krasnov, B., G. Shenbrot, L. Rios and M. Lizurume. Does food-searching ability determine habitat selection? Foraging in sand of three species of

gerbilline rodents. Ecography 23:122-129 (2000)Li, J.-H., M. Sagi, J. Gale, M.Volokita and A. Novoplansky. Response of tomato plants to saline water as affected by carbon dioxide supplementation.

I: Growth, yield and fruit quality. The Journal of Horticultural Science and Biotechnology 74:232-237 (1999)Li, J.-H., J. Gale, A. Novoplansky, S. Barak and M.Volokita. Response of tomato plants to saline water as affected by carbon dioxide supplementation.

II: Physiological and biochemical responses. The Journal of Horticultural Science and Biotechnology 74:238-242 (1999)Li, J.-H., J. Gale,T. Sinai, M.Volokita and A. Novoplansky. Effect of leaf variegation on acclimation of photosynthesis and growth response to elevated

CO2. The Journal of Horticultural Science and Biotechnology 75:679-683 (2000) Lortie, C.J., D.T. Ganey and B.P. Kotler. The effects of gerbil foraging on the natural seedbank and consequences on the annual plant community. Oikos

90:399-407 (2000)Maderson, P.F.A., D.G. Homberger, L. Alibardi,W.J. Bock, A.H. Brush, P. Currie, P.G. Davis, P. Dodson, J.O. Farlow, N. Geist, M. Harris, L.D. Martin, G.K.

Menon, B. Pinshow,W.P. Porter, J. Ruben, R.H. Sawyer, P. Stettenheim, S. Sumida, S.Tarsitano and B.O.Wolf. Symposium on Evolutionary Originof Feathers: Panel Discussion. American Zoology 40:695-706 (2000)

Nathan, R., U.N. Safriel, I. Noy-Meir and G. Schiller. Spatiotemporal variation in seed dispersal and recruitment near and far from Pinus halepensistrees. Ecology 81:2156-2169 (2000)

Plakht, J. Quaternary units in Makhteshim, Negev desert: similarities and peculiarities. Israel Journal of Earth Science 49:179-187 (2000)Plakht, J. Climate-related fluvial morphology in the central Negev desert, Israel. Geolines 11:52-54 (2000)Plakht, J., N. Patyk-Kara and N. Gorelikova.Terrace pediments in Makhtesh Ramon, central Negev, Israel. Earth Surface Processes and Landforms 25:29-

39 (2000)Roxburgh, L. and B. Pinshow. Nitrogen requirements of an old-world nectarivore, the orange-tufted sunbird (Nectarinia osea). Physiological and

Biochemical Zoology 73:638-645 (2000) Saltz, D., M. Rowen, and D.I. Rubenstein.The impact of space use patterns of reintroduced Asiatic wild ass on effective population size. Conservation

Biology 14:1852-1862 (2000)

desertecology 48

Saltz, D. and D.Ward. Responding to a three-pronged attack: Desert lilies subject to herbivory by dorcas gazelles. Plant Ecology 148:127-138 (2000)Saltz, D.Wildlife management. In: Encyclopedia of Biodiversity (Ed. S. Levin), Academic Press, San Diego,Texas, vol. 5, pp. 823-829 (2000)Semenov D.V., G.I. Shenbrot and K.A. Rogovin. Lizards of Mongolian deserts: Densities and community structure. Asiatic Herpetological Research

9:1-9 (2000)Shenbrot, G. and B. Krasnov. Habitat selection along an environmental gradient: Theoretical models with an example of Negev desert rodents.

Evolutionary Ecology Research 2:257-277 (2000)Shkedy,Y. and D. Saltz. Dispersal patterns and fragmentation of Nubian ibex and hyrax populations in Israel. Conservation Biology 14:200-206 (2000) Ward, D., D. Saltz and L. Olsvig-Whittaker. Distinguishing signal from noise: Long-term studies of vegetation in Makhtesh Ramon erosion cirque,

Negev desert, Israel. Plant Ecology 150:27-36 (2000)Whitehouse, M.A.E. and Y. Lubin. Competitive foraging in the social spider Stegodyphus dumicola. Animal Behaviour 58:677-688 (1999) Wilby, A. and M. Shachak. Harvester ant response to spatial and temporal heterogeneity in seed availability: Pattern in the process of granivory.

Oecologia 125:495-503 (2000)Zaady, E., U. Kuhn, B.Wilske, L. Sandoval-Soto and J. Kesselmeier. Patterns of CO2 exchange in biological soil crusts of successional age. Soil Biology

and Biochemistry 32:959-966 (2000)

desertecology 49

Technical staff

Secretarial staff

Visiting Scientists

PostdoctoralFellows

Mitrani Department of Desert Ecology

Yael Bar-Ilan - Hazeva Research and Development Center Sol BrandOfer EitanMarc GoldbergDr.Vasiliy Kravchenko - Hazeva Research and Development CenterMichal Laniado - Ramon Science CenterRegina LevacovZafrir LeviMoris Melnikov - Hazeva Research and Development CenterIris MuslySonia RosinGalit ShiranDror TschoryJum’a Zanun Natali Zeevi - Hazeva Research and Development CenterMarina Zvilikhovsky - Ramon Science Center

Yael KaplanTamar Livne - Hazeva Research and Development CenterRinat LukatsOrli Plotkin - Hazeva Research and Development CenterAvi Shushan - Ramon Science CenterGalit Sudery

M.A Bader - Plant Protection Institute, Giza, Egypt (HRDC)Nico von Breemen - Wageningen University, NetherlandsCarlos Bernstein - University of Claude Bernard, Lyon FranceJoel S. Brown - University of Illinois, ChicagoM.M.M Al Gamal - Plant Protection Institute, Giza, Egypt (HRDC)Frances Duncan - University of the Witwatersrand, South Africa Martin Ebejer - Malta (HRDC)M. Feder - The University of ChicagoGottfried Jetchke - Institute for Ecology, Jena University, GermanyJes Johannesen - University of Mainz, GermanyMiklos Kertes - The Hungarian Academy of SciencesB. Lovegrove - The University of Natal,Pietermaritzburg, South AfricaMarc Mangel - University of California, Santa Cruz Günter Müller - The Museum of Munich; Hebrew University of Jerusalem (HRDC)Beata Oborny - Lorand Eotvos University, BudapestDr.Till Osten - Natural History Museum, Stuttgart (HRDC)M. L. Rosenzweig - University of Arizona,TucsonM.G. Salem - Plant Protection Institute, Giza, Egypt (HRDC)Neil Springate - British Museum, London (HRDC)Andrei Telchovski - The Institute of Ecology and Evolution, Moscow (HRDC)Linda Wiener - St John’s College, Santa Fe, New MexicoJonathan Wright - School of Biological Sciences, University of Wales, Bangor

Dr.Avner Anava - Hazeva Research StationDr. Carmi KorineDr.Thomas RödelDr.Anna SherDr. Phillip TaylorDr. Ian van TetsDr. Kerstin WeigandDr. Mary WhitehouseDr.Andrew WilbyDr. Suba Rao

desertecology 50

Graduate Students

Trainees & VisitingStudents

Tania Acuna Aram AviramNoa AvniAlona BachiShirli Bar David (Tel Aviv University)Michal Ben DrorGil Ben NatanPablo BlinderGil BohrerShlomi BrandwineRami BuchnikAyelet DaninoAnat DumoshZhang FengchunDror HablenaNimrod IsraeliMoses Kirega GichuaAnat LeviZafrir LeviAlex MaklakovRegev ManorNir MaozShai Markman

Keren OrYarden OrenOfer OvadiaAmir Pearlberg (Tel Aviv University)Guy PeerNoam Ra’anan (Hebrew University of Jerusalem)Ornea Reisman-BermanLizanne RoxburghNatalia RuizNir SapirHila ShamirEhud ShaniEyal ShochatMadan ShresthaPirchia SinaiGil StavEric SummerHila Tsahor-Ohayon Sergei VolisGideon WasserbergNimrod Yisraeli Fenchan ZhangIdo Zurim

Tatiana Demidova, (Russia)Chris Lortie (University of British Columbia, Canada)Megan McMaster (South Africa)Todd J. McWhorter (University of Arizona)Kenneth Onacha,Trainee (Kenya)Barbara Ozimek,Trainee (Queens University, Ontario, Canada)Benjamin Zaitchick,Trainee (Harvard University)