86

P rincipes, 40(21, 1996, pp. 86-92

P R I N C I P E S [Vor. 40

Floral Biology and Insect Visitation of theMonoecious Palm Prestoea decurrens onthe Pacific Coast of Golombia

FnN EnvxDepartment of Systematic Botany, lnstitute of Biological Sciences, Uniuersity of Aarhus'

Nordlandsaej 68, B24O Risskoa, Dennark

Roonrco BnRNerInstituto de Ciencias Naturales, (Iniaersidad Nacional de Colornbia, Apartado 7495, Bogotri, Colombia

Assrnecr

We studied the floral biology and insect visitation of themonoecious, protandrous palm Prestoea decurrens H. Wendl.

in Choc6, Colombia. The palm has staminate and pistillatephases of 18 and 7 d duration, respectively. Flowers open in

the late morning and staminate flowers abscise in the afternoonthe same day. Pistillate flowers apparently are at anthesis for2 d, and if not pollinated, abscise on the 3rd d. Both staminateand pistillate flowers are whitish-yellow, with no perceptiblescent. Staminate flowers offer pollen and both flowers producenectar. Flies, bees, wasps, beetles' and one species of crab visitthe inflorescences regularly during staminate anthesis. Only afew insects visit the inflorescences during pistillate anthesis'Due to their foraging at both morphs and high pollen loads we

conclude that halictid bees play the principal role in pollinationfollowed by trigonid bees and small flies.

Prestoea is a genus of small to medium-sized,monoecious palms. The genus belongs to the sub-tribe Euterpeinae of tribe Areceae in subfamilyArecoideae, and consists of I0 species of neo-tropical distribution (Henderson and Galeano, inpress). One species, P. acum.inata (Willd.) H. E.Moore has economic importance for Ecuadorbecause its palm hearts are canned for export(Balslev and Henderson 1987, Borgtoft Pedersenand Balslev L992 as P. trichoclnda (Burret) Bal-slev and Henderson). Most of the other specieshave narrow ranges and none of them is muchused or cultivated. Few notes exist on the polli-nation of Prestoea despite of the accessibility ofthe inflorescences in this genus (Bannister 1970,Bullock 1981). This paper seeks to fill this gapby providing data on the floral biology and insectvisitors of P. decurrens H. Wendl. in Colombia.

Study Sites andObservation Periods

The present study was conducted at two local-ities of slightly disturbed primary wet forest (bos-que nuy hirnedo tropical, according to IGAC1977). Both were located at 0-20 m elevation inthe Department of Choc6, on the Pacific coast ofColombia (Fig. l). Rainfall in the area rangesbetween 5 023 mm at Bahia Solano in the north(HIMAT 1993) and B 080 mm per year at EIAmargal in the south (Fundaci6n Ingued6 1994).Investigations were carried out on scattered indi-viduals in a 1.5-ha "tagual" (periodically inun-dated vegetation dominated by the palm Phyt-elephas seemannii O. F. Cook.) and nearby hillsnear the mouth of Rio Sampichi in the ParqueNacional Utria through March and April 1994.Additional insect collections and observations weiemade at El Amargal Biological Station in May1994.

Methods

Seven palms bearing l0 inflorescence buds andexposed inflorescences were tagged for observa-tions. Individual pistillate flowers were markedwith a water-based marker pen in order to studytheir development. The flowering sequence andinsect activity were recorded on daily visits. Insectvisitors to the staminate flowers were observed for6 h and to the pistillate flowers for 5 h. Thepresence and position of nectaries were testedusing glucose testing paper (Clinistix@). A solutionof neutral red that stains fatty substances (includ-

re96l ERVIK AND BERNAL: FLORAL BIOLOGY OF PRESTOEA DECURRENS

Bohio

El\bild

a(

o

PACIFIC OCEAN

GOLFODETRIBUGA

Nuqui

(couoYorrienres

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b\----t.-r- ,rl

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\ \ o \ I\ \ - ,

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urRrA \ i,^q9. NATIONAL PARK \

76o00l

It

/,'----i -Y*"Ho'Jurubido'

ibugd50

Arusf

o 5 r o 1 5 2 0 2 5-

l. Location of the Gulf of Tribug6. Study sites are marked with stars.

P R I N C I P E S [Vor-. 40

sPsPsP

++++++++++++++++++#+

+++*++i*********+*++++++++++++t

+#+#+++++++++++++++++++++++++

- 2. Inflorescence oI Prestoea d'ecurrens.

ing oil-containing cells) was used to test for thepresence of pollen kitt and scent-producing floralparts (Vogel 1990). The temperature ofa selectedinflorescence was measured before and after split-ting of the peduncular bract. A digital thermom-eter with a 2 mm diameter probe was inserted inthe center of the bud or flower-bearing parts. Inorder to reveal the specfficity of the visitors toPrestoea decunens, insects were also collectedon several co-existing palm or palmJike species,including Cocos nucifera L., Phytelephas see-mannii O. F. Cook, Welf.a regia H. Wendl. exAndr6 (Palmae), Asplundia sp., and Carludoaicapalmata Ruiz and Pav. (Cyclanthaceae). Vouch-ers of the palm have been deposited at AAU, COL,and FMB. Insect vouchers have been depositedin the entomological collections at Instituto deCiencias Naturales, Universidad Nacional deColombia, at INDERENA, BogotS, at the Zoolog-ical Museum, University of Aarhus, and at therespectiye institutions of the specialists that helpedwith identifications. Numbers are given to some

Daily vuiation in onwt md end of flowering

xxxxxsxn Genemlflowering

High rctivity

++++++++ lrwer rctivity

3. The diurnal pattern of visitation of the different insect

groups to inflorescences of Prestoea decurrens in relation to

flowering. S: visitation to staminate phase inflorescences. P:visitation to pistillate phase inflorescences.

of the species and one genus in order to make

possible comparisons with other publications of thespecialists (see Acknowledgments) or the authors.

Results

Prestoea. decurrens is a medium-sized cespitosepalm with 2-7 stems up to 7 m tall and 12 cmin diameter. It is common along rivers and streamsin Iowland wet forests from Nicaragua to westernEcuador. Inflorescences of P. decurrens arebranched to one order with 36-68 rachillae (X:50.3, 1[: 7) (Fig. 2) that are enclosed in bud bya single, slender peduncular bract. Flowers areunisexual and generally grouped in triads of twolateral staminate and one central pistillate flower.The development of the pistillate flowers is oftensuppressed at the distal end of each rachillae,resulting in staminate dyqds. Each rachilla bearsfrom 206 to 320 triads (X : 268.3,1f : 4) andfrom two to 18 dyads (X: 6.5, N: 4). Flowersof both morphs are whitish-yellow with no per-ceptible odor. The filaments and the connectivesstained weakly red with neutral red. This mayindicate that these tissues produce a very weakscent. No other tissues in the inflorescence changedcolor. Staminate flowers offer pollen and both sta-minate and pistillate flowers produce nectar. Pol-len of P. decunens is sticky. It stained whentreated with neutral red, which indicates presenceof pollen kitt.

The individuals studied flowered throughout theperiod of observation; and the presence of buds

Time of Day06 08 10 12 14 16 18

staminate flowedng ----xxxxxxx-------

r9961 ERVIK AND BERNAL: FLORAL BIOLOCY OF PRESTOEA DECURRENS

Table 1. Visitors to the inf.orescences olfPrestoea decurrens. Relatiae abundances are indicatedas follows: aery common (***), con'nrlon (**), ur"o*rnon (*), and not obseraed ( ). Localitiesat which the insects were obserued: A: El Amalgal, S : Sampichl. Insects obseraed on other hostswere marked with a nurnber and letter (s : staminate, p : pistillate) referring to host plantspecies and its phase. Cocos nucifera (1), Phytelephas seemannii (2) , WeIfra regia (3), Asplundia

sp. (4) , and Carludovica palmata (5) .

B9

Order,/FamilySubfamily or tribe

StaminatePhase

Pisti.late Other

Phase Locality Hosts *

Coleoptera

ChrysomelidaeAlticinae

GalerucinaeCurculionidae

Baridinae, CentrininiCholinaeErirhininae, Derelomini

StaphylinidaeAleocharinae

Diptera

Cecidomyidae

ChloropidaeDrosophilidae

- MilichiidaeMycetophilidae

Hymenoptera

ApidaeMeliponinae

Halictidae

Dempoda

Grapsidae

Brasilaphthona sp. 2Near Centralaphthona sp. INear C. sp. 3Hypolampsis sp. 3Monolepta sp.

Bondariella sp. 3Cholus cananchensis HellerPhyllotrox sp. 27P. sp. 28Genus 2, sp. I

Amazoncharis?

Cecidomldae sp. IC. sp. 2C. sp. 3Chloropidae sp. IDrosophila sp.Milichiidae sp. IMycetophilidae sp. I

Plebeia aff. minima (Gribodo)Trigona spinipesT. uilliana FrieseDialictus sp.Neocorynura sp.Undet. sp. IUndet. sp. 2Undet. sp. 3

Sesarma cf. miersii Rathbun

A , SSS 2s/pA , SA , SA , SSS

S

ASSAA

SA , SS* sS

SsSASAS

4s, 5s5s5s

of different degrees of development suggests thatthis species flowers throughout the year, a factconfirmed by G. Galeano (personal communica-tion). Prestoea decurrens is protandrous with nooverlap between staminate and pistillate phases.All flowers are closed at the splitting of the bractand no insects are present. This situation may lastfor up to I d until 9:00 to ll:30 a.m. when thefirst staminate flowers open and anthers dehisce(Fig. 3). Individual staminate flowers are only at

anthesis for a few hours and abscise in the after-noon the same day. The staminate phase of theinflorescence lasts 18 d, with daily pulses of upto I 000 flowers per inflorescence. Then there isa pause lasting two days which is followed by apistillate phase seven days long. Pistillate flowersalso open between 9:00 and I l:30 a.m. The stig-mas remain humid and whitish-yellow for 2 d andare probably receptive this long. On the 3rd dthey turn brownish, and the flowers either drop

P R I N C I P E S lVoL. 40

off or start to develop into fruits. No rise in tem-perature was recorded before or during anthesis.

At least 26 species of insects and one speciesof crab regularly visited the inflorescences of P.decurrens during the staminate phase (Fig. 3,Table l). Halictid bees came in tens and were themost conspicuous and numerous insects. Theymoved along the rachillae and busily collectedpollen. We observed that at least one species storedpollen grains on the ventral side of its body. Eachinsect usually foraged for several minutes beforeIeaving. Also meliponid bees collected pollen, butthey were usually fewer than the halictids. Smallflres (Drosophila, Chloropidae, Milichiidae, Oti-tidae) often visited the staminate flowers by thetens. They were all observed to forage on nectar.Whether they also eat pollen is unclear. Less than30 individuals of small chrysomelids and curcu-Iionids visited the inflorescences particularly dur-ing daytime. They fed on pollen grains and nectarand used the inflorescence as a site for copulation.Usually a few individuals (< 5) deviated by stayingover night on the inflorescences, mostly restinginactive along the rachillae. The most conspicuousof the beetles was Cholus cananchensis, a l0 mmlong, yellow and black curculionid. A few of them(<10) stayed on the rachillae for hours, oftenwith the purpose of copulating. All beetles werepassive and rarely arrived and left the inflores-cences compared with the bees and most of theflies. A nectar-eating crab (Sesarma cf. miersii)visited the staminate flowers during daytime. Typ-ically tivo or three individuals at a time clung tothe rachillae while feeding on nectar using theirclaws. These crabs mostly ascended in the morningand descended in the afternoon the same day.

There were fewer visitors to the inflorescencesin the pistillate phase in terms of both individualsand species (Fig. 3). During a 5-h period of obser-vations at a particular inflorescence during pistil-Iate anthesis, the following insects were recordedas visitors: =50 Cecidomyidae and Mycetophili-dae, l5 Drosophilidae, five Halictidae, three smallunidentified Diptera, two Meliponidae, one Otiti-dae (?), one Phyll,otror, and one small unidentifiedbeetle (Table l). They all foraged on nectar. Thebees moved from flower to flower and often touchedthese with their mouthparts, their legs, and theirabdomen. They typically visited two or threerachillae before leaving.

We have no data on fruit set, but we observedthat a Madarini weevil (Baridinae, Curculionidae)frequently bored holes in unripe fruits, which sub-

sequently dried out. This fruit predator was com-mon at both localities.

Discussion

Inflorescence phenology of P. decurrens inColombia follows the pattern described by Bullock(I9Bl) for the same species in Costa Rica, wherehowever, the staminate phase lasted only 10-14d, and the pistillate phase only 3 d. The pause''between the two phases was similar at both local-ities. Fertilization of a flower by another from thesame plant (geitonogamy) in this species is prob-ably a rare phenomenon. First, there is no overlapof staminate and pistillate phases of one inflores-cence. Second, consecutive inflorescences on thesame stem usually have a great difference in devei-opmental stage; thus when an inflorescence entersthe staminate phase, the pistillate phase of theprevious inflorescence has passed several weeksago. Third, the probability of simultaneous sta-minate and pistillate phases on different stems ofthe same cluster is low because there are few stemsin each cluster (mostly I-4), and flowering appearsto occur throughout the year.

Wind pollination of P. decurrens is probablyinsignificant because pollen apparently has pollenkitt and therefore is sticky, and because winds inthe habitat of this palm are rarely of any strength.We also rule out the importance of beetles inpollination, although a few of them were presentboth at staminate and pistillate anthesis. First, theywere typically staying passive for hours and rarelyvisited the flowers to feed on nectar and pollen.Second, they rarely moved between inflores-cences. Also the crab was sedentary and thereforeprobably did not contribute to pollination.

Diptera were the most common visitors to femaleinflorescences in terms of number of individuals.However, none of them belonged to the groupsknown as efficient pollinators, as, e.g.; Syrphidae.For various reasons we consider the role of fliesvisiting P. decurrens less important than the bees.To begin with, the flies were more passive thanthe bees when visiting an inflorescence. Next, com-pared with the bees, flies rarely traveled betweeninflorescences. AIso, all the flies visiting P. decur-retus were very small and usually sparsely haired,and therefore incapable of transporting Iarge loadsof pollen grains. Additionally, the flies were rarerthan the bees on staminate inflorescences. Schmid(1970) cited the same reasons to rule out smallflies as pollinalors of Asterogrye martiana (Mart.)

fI

fI

{

19961

H. Wendl., and different studies have actuallydemonstrated that drosophilids did not carry anyor only little pollen when visiting pistillate flowersof the palmsliphanes erinacea(Karst.) H. Wendl.(Borchsenius I 993), Aphandra natalia (Hender-son & Balslev) Barfod (Ervik 1993), and. Phy-telephas seemannii (Bernal and Ervik, in press).

The meliponids usually collect pollen on manydifferent taxa of plants (Heithaus 1979) (i.e., theyare polytropic, see Grant 1949, Eaegri and vander Pijl l9B0) and Trigona williana was muchmore abundant at the inflorescences of the nearbyand abundantly flowering Phytelephas seemannii(Bernal and Ervik, in press). The probability wastherefore high that the meliponids brought moreforeign than co-specific pollen when visiting pis-tillate flowers of P. d.ecurrezs. The halictids, incontrast, were oligotropic (visiting some relatedtaxa ofplants only) or apparently even monotropic(visiting one single or some closely related plantspecies only). We never observed them on anyother plant species. There is therefore a highchance that they bring exclusively co-specific pol-len. Both the behavior and abundance of the ha-lictids (Table l) and their potentially large pollenloads suggest that they were the most importantpollinators of P. decurrens. Populations of beesare, however, often varying in both compositionand size during the year. This phenomenon iscorrelated with the degree of sociality: eusocialbees are less seasonal than solitary bees (Heithaus1979). The family Halictidae exhibits a wide rangeof social systems. We do not know the degree ofsociality or seasonality of the Halictidae visitingP. decurrens and therefore cannot rule out thepossibility that the fauna of bees pollinating Pres-toea decurrens changes during the year. Bullock(I9Bl) observed a whole set of different speciesof bees visiting P. decurrens flowers in Costa Ricafrom December to September. These included twospecies of Trigona, or'e Neocorynura, orreLasioglossum, and one unidentified Halictidae.Bullock suggested that bees were the pollinators,but did not point to any species as being partic-ularly important.

The general morphology and phenology inPrestoea agree well with the syndrome of beepollination (melittophily) in palms suggested byHenderson (1986). Melittophily is likely to be awidespread pollination syndrome in Prestoea. Astudy by Bannister (1970) supports this assump-tion. She reported rhal Prestoea acumina'tcr'(Willd.) H. E. Moore (as Euterpe globosaGaertn.)

ERVIK AND BERNAL: FLORAL BIOLOGY OF PRESTOEA DECURRENS 9 I

II

II

was protandrous with a very short overlap betweenstaminate and pistillate phases in Puerto Rico. Sheconsidered "honeybees and small flieso' to be pol-linators.

In the palm family melittophily along with can-tharophily and myiophily are considered the major

- pollination syndromes (Henderson 1986). Laterstudies have added new documentation to thisstatement (Zona I9B7 ,Bagh L996). Halictid bees,however, have not been addressed any specialattention, although they often visit palms (Olesenand Balslev 1990) and also participate in the pol-lination of at least some palms including Sobol(Zona I9B7 and references therein).

Acknowledgments

Support for F. Ervik came from the EEC (grantNo. TS3-CT91-004). R. Bernal thanks the Uni-versidad Nacional de Colombia, for a leave ofabsence, DANIDA for a study fellowship, and TheCharles A. Lindbergh and Anne Morrow Lind-bergh Foundation, Conservation International,Fundaci6n Ingued6, and The International Foun-dation for Science, for support of different stagesof the research. INDERENA and the ColombianMinistry of Environment (particularly A. Repizzo,L. A. Escobar, and park personnel) facilitated fieldwork in the Utria National Park. S. Fern6ndezprepaied the map. We are grateful to the followingspecialists who identified the visitors: R. W. FIow-ers (Chrysomelidae), D. A. Grimaldi (Drosophilidae, Milichiidae, Chloropidae), G. Nates (Apidae),C. W. O'Brien (Curculionidae), M. Rocha (Grap-sidae), D. Roubik (Apidae). We also want to thankA. Barfod and A. Henderson for critical readineof the manuscript.

Lrrnnerune CIrro

BALSLEv, H. ano A. HENDERSoN. 1987.. Presloea Palmito.Pr incipes 3I : I I .

BaNttsmn, B. A. 1970. Ecological life cycle of Euterpeglobosa Gaerrn. In: H. T. Odum and R. F. Pigeon (eds.).A tropical rain forest: a study of irradiation and ecology.Atomic Energy Comission, Oak Ridge, Temessee, U.S.A.

BERNAL, R. AND F. EnvIr. In press. Florhl biology andpollination of the dioecious palm Phytelephas seemanniiin Colombia: an adaptation to staphylinid beetles. Biotro-plca.

BocH, A. 1996. The phenology and pollination biology ofIorr Calamus (Arecaceae) species in Thailand. Principes4 0 ( l ) : 5 - I 5 .

BoRCHSENIUS, F. 1993. Flowering biology and insect visi-tation of three Ecuadorean Aiphanes species. Principes37 : I 39 -150 .

P R I N C I P E S [VoL. 40

BoRGToFT PEDERSEN, H. euo H. Bersrtv. 1992. Economicbotany oiEcuadorean palms. 1z: M. Plotkin and L. Famo-lare (eds.). Sustainable harvest and marketing of rainforest products. Island Press, Covelo, California' pp. 173I 9 I .

BuLLocK, S. H. 1981. Notes on the phenology of inflores-cences and pollination of some rain forest palms in CostaRica. Pr incipes 25: I0 l -105.

ERVIK, F. 1993. Notes on the phenology and pollination of. the dioecious palms Mauritia f.exuosa (Calamoideae) and

Aphand.ra natalia (Phytelephantoideae) in Ecuador. 1uW. Barthlott, C. M. Naumann, K. Schmidt-Loske, andK. L. Schuchmann (eds.). Animal-plant interactions intropical enviroments. Zoologisches Forschungsinstitut mdMuseum Alexander Koenig, Bonn, pp.7 12.

Fercnt, K. enn L. veN lrn Pur. 1980. The principles ofpollination ecology, 3rd revised ed. Pergamon Press,Oxford.

Funoect6N INGUED6. 1994. Unpublished rainfall data atEl Amargal Biological Station. Fundaci6n Ingued6, Bogoti'.

Gnarvr, V. 1949. Pollination systems as isolating mechanismsin angiosperms. Evolution 3: 82-97.

HEITHAUS, E. R. 1979. Community structure ofneotropicalflower visiting bees and wasps: diversity and phenology.Ecolosv 60: 190-202.

News from North Queensland

The North Queensland Palm Society (NQPS)met on February 5 at Tumbetin Lodge, The Pal-metum, Townsville. Bob Smyth, from the Chem-ical Department, James Cook University, spoketo the group on chemicals in the garden.

The group met again on March 4 and scheduledfurther 1996 general meetings for April l, May6, June 3, July I, August 5, September 2, October7, and November 4, all at Tumbetin Lodge startingat 7:30 p.m. In addition there will be a PalmLovers' Weekend held during the Queen's Birth-day weekend celebration on June B-9, since lastyear's celebration was such an overwhelming suc-CESS.

There will also be a PACSOA weekend on Octo-ber 1l-13, in conjunction with the TownsvilleBranch and Friends of the Palmetum. This willfeature Don Hodel from California, author of"Chamaedorea Palms," Ray Osborne from Africa,John Dowe, and two others yet to be confirmed.

HENDERSoN, A. 1986. A review of pollination studies in thePalmae. Botanical Review 52: 227-259.

euo G. GarreNo. In press. Euterpe, Prestoea, andNeo n i c h ol son i a. Flora Neotropica.

HIMAT. 1993. Unpublished data from the meteorologicalstation at Bahia Solano. Computer printout, Instituto Co-lombiano de Meteorologia, Hidrologia y Adecuaci6n oeTierras, Bogot6.

IGAC. 1977. Zonas de vida o formaciones vegetales deColombia. Instituto Geogr6fico Agustin Codazzi, Bogot6.

OLESEN, J. M. aNl H. Bersrrv. 1990. Flower biology andpollinators of the Amazonian monoecious palm Geonoma ,macrostachys: a case of Bakerian mimicry. Principes 34:l 8 l - 1 9 0 .

ScHMID, R. 1970. Notes on the reproductive biology ofAsterogyne martiana (Palmae). II. Pollination by syrphidflies. Princioes 14: 39-49.

Vocrr, S. 1990. The role of scent glands in pollination.Smithsonian Institute Libraries, Washington, D.C. (Englishtranslation, German original published in 1963).

Zone, S. 1987. Phenology and pollination biology of Sabaletonia (Palmae) in Southeastern Florida. Principes 3i:r77-r82.

Year 1996 will culminate on December 2 withthe Society Christmas Party. NQPS Officers for1996 are: Lorraine Tooth, President and Trea-surer; Jill Whatley, Vice President; Kerry Rob-ertson, Secretary.

News from Mackay andRockhampton

(Queensland, Australia)

Six members of The Palm and Cycad Societyof Mackay (branch of PACSOA) traveled to Rock-hampton on December 2-3, 1995, as guests ofthe Rockhampton Palm and Cycad Society. Visitswere made to the garden of Allan and JennyMoorhead, followed by the Rockhampton BotanicGardens. In addition to viewing the many plants,members were given a taste of a rare fruit, Grum-ichamas. Palms featured in the RockhamptonBotanic Gardens included lovely specimens of

CHAPTER NEWS AND EVENTS(Bv Jim Cain unless otherwise noted)

(Continued on p. 111)