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The ecological niche, function of a species in the community Resource utilization functions (RUFs) Competitive communities in equilibrium with their resources Hutchinson ’ s n-dimensional hypervolume concept Euclidean distances in n- space (Greek mathematician, 300 BC) Fundamental versus Realized Niches

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Resource matrices of utilization coefficients Niche dynamics Niche dimensionality and diffuse competition Complementarity of niche dimensions Niche Breadth: Specialization versus generalization. Similar resources favor specialists, different resources favor generalists Periodic table of lizard niches (many dimensions) Thermoregulatory axis: thermoconformers —> thermoregulators

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Experimental Ecology Controls Manipulation Replicates Pseudoreplication Rocky Intertidal Space Limited System Paine ’ s Pisaster removal experiment Connell: Balanus and Chthamalus Menge ’ s Leptasterias and Pisaster experiment Dunham ’ s Big Bend saxicolous lizards Brown ’ s Seed Predation experiments Simberloff-Wilson ’ s defaunation experiment

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R. T. Paine (1966)

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Joseph Connell (1961)

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Bruce Menge (1972)

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Menge 1972 Bruce Menge

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Grapevine Hills, Big Bend National Park Sceloporus merriami and Urosaurus ornatus Six rocky outcrops: 2 controls, 2 Sceloporus removal plots and 2 Urosaurus removal areas. ======================================================== 4 year study: 2 wet and 2 dry: insect abundances Monitored density, feeding success, growth rates, body weights, survival, lipid levels Urosaurus removal did not effect Sceloporus density No effects during wet years (insect food plentiful) Insects scarce during dry years: Urosaurus growth and survival was higher on Sceloporus removal plots Arthur Dunham

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James Brown Dipodomys kangaroo rats Pogonomyrmex harvester ants

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Experimental Design of Seed Predation in the Chihuahuan Desert ___________________________________________________ PlotsTreatments ___________________________________________________ 11,14Controls 6,13Seed addition, large seeds, constant rate 2,22Seed addition, small seeds, constant rate 9,20Seed addition, mixed seeds, constant rate 1,18Seed addition, mixed seeds, temporal pulse 5,24Rodent removal, Dipodomys spectabilis (largest kangaroo rat) 15,21Rodent removal, all Dipodomys species (kangaroo rats) 7,16Rodent removal, all seed-eating rodents 8,12Pogonomyrmex harvester ants 4,17All seed-eating ants 3,19All Dipodomys plus Pogonomyrmex ants 10,23All seed-eating rodents plus all seed-eating ants ___________________________________________________________ Munger, J. C. and J. H. Brown Competition in desert rodents: an experiment with semipermeable enclosures. Science 211:

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open circles = rodents removed solid circles = controls

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Defaunation Experiments in the Florida Keys Islands of mangrove trees were surveyed and numbers of arthropod species recorded Islands then covered in plastic tents and fumigated with methyl bromide Islands then resurveyed at intervals to document recolonization Simberloff and Wilson 1970

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Evidence for Stability of Trophic Structure? First number is the number of species before defaunation, second in parentheses is the number after _______________________________________________________________________________________ Trophic Classes ______________________________________________________________________________ Island H S D W A C P ? Total _______________________________________________________________________________________ E1 9 (7)1 (0)3 (2)0 (0)3 (0)2 (1)2 (1)0 (0)20 (11) E211 (15)2 (2)2 (1)2 (2)7 (4)9 (4)3 (0)0 (1)36 (29) E3 7 (10)1 (2)3 (2)2 (0)5 (6)3 (4)2 (2)0 (0)23 (26) ST2 7 (6)1 (1)2 (1)1 (0)6 (5)5 (4)2 (1)1 (0)25 (18) E7 9 (10)1 (0)2 (1)1 (2)5 (3)4 (8)1 (2)0 (1)23 (27) E9 12 (7)1 (0)1 (1)2 (2)6 (5) 13 (10)2 (3)0 (1)37 (29) Totals 55 (55)7 (5) 13 (8)8 (6) 32 (23) 36 (31) 12 (9) 1 (3) 164 (140) _______________________________________________________________________________________ H = herbivore S = scavenger D = detritus feeder W = wood borer A = ant C = carnivorous predator P = parasite ? = undetermined

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Wilson 1969

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Predation and Parasitism

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Predator-Prey Experiments Georgii F. Gause

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Predator-Prey Experiments Georgii F. Gause

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Predator-Prey Experiments Georgii F. Gause

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Lotka-Volterra Predation Equations coefficients of predation, p 1 and p 2 dN 1 /dt = r 1 N 1 – p 1 N 1 N 2 dN 2 /dt = p 2 N 1 N 2 – d 2 N 2 No self damping (no density dependence) dN 1 /dt = 0 when r 1 = p 1 N 2 or N 2 = r 1 / p 1 dN 2 /dt = 0 when p 2 N 1 = d 2 or N 1 = d 2 / p 2 Alfred J. Lotka Vito Volterra

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Neutral Stability (Vectors spiral in closed loops)

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Vectors spiral inwards (Damped Oscillations)

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Damped Oscillations

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Vectors spiral inwards (Damped Oscillations) Prey self damping

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Mike Rosenzweig Robert MacArthur

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Mike Rosenzweig Robert MacArthur

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Moderately efficient predator Neutral stability — Vectors form a closed ellipse. Amplitude of oscillations remains constant. <— Mike Rosenzweig Robert MacArthur —>

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Unstable — extremely efficient predator Vectors spiral outwards until a Limit Cycle is reached Robert MacArthur —> <— Mike Rosenzweig

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Damped Oscillations — inefficient predator Vectors spiral inwards to stable equilibrium point Robert MacArthur —> <— Mike Rosenzweig

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Functional response = rate at which Individual predators capture and eat more prey per unit time as prey density increases C. S. Holling

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Numerical response = increased prey density raises the predator ’ s population size and a greater number of predators consume An increased number of prey

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Gause’s Didinium Experiments Lotka-Volterra Predation Equations: N 1 N 2 = Contacts coefficients of predation, p 1 and p 2 dN 1 /dt = r 1 N 1 – p 1 N 1 N 2 dN 2 /dt = p 2 N 1 N 2 – d 2 N 2 No self damping (no density dependence) dN 1 /dt = 0 when r 1 = p 1 N 2 or N 2 = r 1 / p 1 dN 2 /dt = 0 when p 2 N 1 = d 2 or N 1 = d 2 / p 2 Neutral Stability Prey Refuges Functional and Numerical Responses

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Adding Prey self-damping stabilizes Prey-Predator isocline analyses Predator efficiency, Prey escape ability Prey refuges, coevolutionary race Predators usually destabilizing

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Prey Isocline Hump Efficient Predator —> unstable Inefficient Predator —> stable Predator Switching, frequency dependence, stabilizes “Prudent” Predation and Optimal Yield Feeding territories Consequence of senescence

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Predator Escape Tactics Aspect Diversity Cryptic coloration (countershading) Disruptive coloration Flash coloration Eyespots, head mimicry Warning (aposematic) coloration Alarm signals Hawk alarm calls Selfish callers Plant secondary chemicals

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