Lecture # 197 November 2017

Second ExamMean = 57.4Range: 3286N = 67

F D’s C- C C+ B’s A- A 9 10 13 9 8 12 4 2

|| || | | | |||

Summary of Direct Pairwise Interactions Between Two Populations__________________________________________________________________________

Species Type of Interaction A B Nature of Interaction __________________________________________________________________________ Competition – – Each population inhibits the other Predation, parasitism, + – Population A, the predator, parasite, and Batesian mimicry or mimic, kills or exploits members of population B, the prey, host, or model

Mutualism, + + Interaction is favorable to both (can Müllerian mimicry be obligatory or facultative)

Commensalism + 0 Population A, the commensal, benefits

whereas B, the host, is not affected

Amensalism – 0 Population A is inhibited, but B is

unaffected

Neutralism 0 0 Neither party affects the other__________________________________________________________________

Lecture # 197 November 2017

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

bees —> clover

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

bees ——> clover

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

mice ——o bees ——> clover

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

cats —o mice ——o bees ——> clover

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

spinsters —> cats —o mice —o bees —> clover

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

spinsters —> cats —o mice —o bees —> clover —> beef

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

spinsters —> cats —o mice —o bees —> clover —> beef —> sailors

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

spinsters —> cats —o mice —o bees —> clover —> beef —> sailors —> naval prowess

Indirect Interactions

Darwin — Lots of “Humblebees” around villages

spinsters —> cats —o mice —o bees —> clover —> beef —> sailors —> naval prowess

Path length of seven! Longer paths take longer (delay)Longer paths are also weaker, but there are more of them

—————————————————>

Indirect Interactions

Trophic “Cascades” Top-down, Bottom-up

Competitive Mutualism

Complex Population Interactions

Rob Colwell

Mutualistic Interactions and Symbiotic RelationshipsMutualism (obligate and facultative) Termite endosymbiontsCommensalisms (Cattle Egrets)

Examples:Bullhorn Acacia ant colonies (Beltian bodies)Caterpillars “sing” to ants (protection)Ants tend aphids for their honeydew, termites cultivate fungiBacteria and fungi in roots provide nutrients (carbon reward)Bioluminescence (bacteria)Endozoic algae (Hydra), “kidnapped” chloroplastsEndosymbiosis (Margulis) mitochondria & chloroplastsBirds on water buffalo backs, picking crocodile teethFigs and fig wasps (pollinate, lay eggs, larvae develop)

Brown Hydra Green Hydra

Nudibranchs

Green sea slug

Hydra

Intraspecific competition (between individuals within spp.)

Interspecific competition (between members of different spp.)

Exploitation competition (resource depression)

Interference competition (direct antagonistic encounters)

Euglossine beesOrchid fragrances (epiphytes)Male bees use orchid chemicals as base for production of pheromones to attract female bees (travel up to 23 km) pollinate rare and diverse orchids, allowing sparsely

distributed plants to occur at astonishing low densities

Dan Janzen

Heliconius tropical butterfliesget amino acids from pollen

Larry Gilbert

Various Aspects of the Association of Cattle Egrets with Cattle________________________________________________________

Number ofNumber Percent Associated Egrets

Category of Cattle Cattle Expected Observed___________________________________________________________________

Grazing in sun 735 39.1 239 439Grazing in shade 55 2.9 18 21Standing in sun 146 7.8 48 46Standing in shade257 13.7 84 17Lying in sun 503 26.8 164 69Lying in shade 143 7.6 47 17Walking 39 2.1 13 3

______________________Total 1878 100.0 612 ________________________________________________________

Various Aspects of the Association of Cattle Egrets with Cattle______________________________________________________________________

Number of Times Mean Count Was Higher

Number Than for Opposite Number of Per Minute Egret Associated Egrets

______________________________________________________________________Feedings, N = 84

Associated 2.34 58 69Nonassociated 1.71 26 31

Steps, N = 62Associated 20.1 7 11Nonassociated 32.1 55 89

Feeding/step, N = 59Associated 0.129 52 88Nonassociated 0.051 7 12

__________________________________________________________

Harold Heatwole

Interspecific Competition leads to Niche Diversification

Two types of Interspecific Competition:

Exploitation competition is indirect, occurs when a resource is in short supply by resource depression

Interference competition is direct and occurs via antagonistic encounters such as interspecific territoriality or production of toxins

Direct versus Indirect InteractionsExploitation vs. Interference competitionApparent CompetitionCompetitive MutualismFacilitationFood Chain MutualismTrophic Cascades (top-down, bottom up)Complex Population Interactions (Colwell’s Plant-Pollinator System)MutualismsEuglossine bees and orchidsHeliconius butterflies (larval nitrogen reserves)Cattle Egret CommensalismGause’s Paramecium competition lab experiments

Competitive Exclusion

Georgii F. Gause

Coexistence of two species of Paramecium

G. F. Gause

Outcome of Competition Between Two Species of Flour Beetles_______________________________________________________________________________

Relative

Temp. Humidity Single Species (°C) (%) Climate Numbers Mixed Species (% wins)

confusum castaneum_______________________________________________________________________________ 34 70 Hot-Moist confusum = castaneum 0 10034 30 Hot-Dry confusum > castaneum 90 1029 70 Warm-Moist confusum < castaneum 14 8629 30 Warm-Dry confusum > castaneum 87 1324 70 Cold-Moist confusum <castaneum 71 2924 30 Cold-Dry confusum >castaneum 100 0

_______________________________________________________________________________

Thomas Park

Recall the Verhulst-Pearl Logistic Equation

dN/dt = rN [(K – N)/K] = rN {1– (N/K)}

dN/dt = rN – rN (N/K) = rN – {(rN2)/K}

dN/dt = 0 when [(K – N)/K] = 0

[(K – N)/K] = 0 when N = K

dN/dt = rN – (r/K)N2

Inhibitory effect of each individualOn its own population growth is 1/KAssumes linear response to crowding,

instant response (no lag), r and K are fixed constants

S - shaped sigmoidal population growth

Verhulst-Pearl LogisticK2 O

Optimal Yield

Sigmoidal population growth

Lotka-Volterra Competition Equations

competition coefficient

ij = per capita competitive effect

of one individual of species j on the rate of increase of species i

dN1 /dt = r1 N1 ({K1 – N1 – 12 N2 }/K1)

dN2 /dt = r2 N2 ({K2 – N2 – 21 N1 }/K2)

Solve for Isoclines by setting dN/dt‘s equal to zero:(K1 – N1 – 12 N2 )/K1 = 0 when N1 = K1 – 12 N2

(K2 – N2 – 21 N1 )/K2 = 0 when N2 = K2 – 21 N1

Alfred Lotka Vito Volterra

Resultant Vectors

Saddle Point

Point Attractor

Lotka-Volterra Competition Equations for n species (i = 1, n):

dNi /dt = riNi ({Ki – Ni – ij Nj}/Ki)

Ni* = Ki – ij Nj where the summation is over j from 1 to n, excluding i

Diffuse Competition ij Nj

Robert H. MacArthur

Lotka-Volterra Competition Equations

for 3 species:

dN1 /dt = r1 N1 ({K1 – N1 – 12 N2 – 13 N3 }/K1)

dN2 /dt = r2 N2 ({K2 – N2 – 21 N1 – 23 N3 }/K2)

dN3 /dt = r3 N3 ({K3 – N3 – 31 N1 – 32 N2 }/K3)

Isoclines: dN/dt = 0 {curly brackets, above}(K1 – N1 – 12 N2 – 13 N3 ) = 0 when N1 = K1 – 12 N2 – 13 N3

(K2 – N2 – 21 N1 – 23 N3 ) = 0 when N2 = K2 – 21 N1 – 23 N3

(K3 – N3 – 31 N1 – 32 N2 ) = 0 when N3 = K3 – 31 N1 – 32 N2

Lotka-Volterra Competition Equations for n species

(i = 1, n):

dNi /dt = riNi ({Ki – Ni – ij Nj}/Ki)

Ni* = Ki – ij Nj

where the summation is over j from 1 to n, excluding i

Diffuse Competition ij Nj

Alpha matrix of competition coefficients

11 12 13 . . . 1n

21 22 23 . . . 2n

31 32 33 . . . 3n

. . . . . . .

. . . . . . .

n1 n2 n3 . . . nn

Self damping elements on the diagonalii equal 1.

Evidence of Competition in Natureoften circumstantial

1. Resource partitioning among closely-related sympatric congeneric species (food, place, and time niches) Complementarity of niche dimensions2. Character displacement, Hutchinsonian ratios3. Incomplete biotas: niche shifts4. Taxonomic composition of communities

Major Foods (Percentages) of Eight Species of Cone Shells, Conus, on Subtidal Reefs in Hawaii_____________________________________________________________

Gastro- Entero- Tere- OtherSpecies pods pneusts Nereids Eunicea belids Polychaetes______________________________________________________________ flavidus 4 64 32lividus 61 12 14 13pennaceus 100abbreviatus 100ebraeus 15 82 3sponsalis 46 50 4rattus 23 77imperialis 27 73______________________________________________________________

Alan J. Kohn

Resource Matrix (m x n)

Radula

MacArthur’s Warblers (Dendroica)

Robert H. MacArthur

Time of Activity Seasonal changes in activity times

Ctenotus calurus Ctenophorus isolepis

Complementarity of Niche Dimensions, page 276

Thomas W. Schoener

Anolis

Prey size versus predator size

Peter R. Grant

David Lack“Darwin’s Finches”

Galápagos Finches

Character Displacement in Hydrobia mud snails in Denmark (Thomas Fenchel)

Snail shell length, mm

Corixid Water BoatmanG. E. Hutchinson

Hutchinsonian Ratios