【正文】 hree types (cont.) ? Type III: Feeding rate is similar to logistic curve。t see the population in question? PredatorPrey Models – Prey isoclines have characteristic hump shape (cont.) ? Below the isocline, prey populations increase – Predator isoclines ? Threshold density, where predator population will increase ? Predator population can increase to carrying capacity PredatorPrey Models – Predator isoclines (cont.) ? Mutual interference or petition between predators – More prey required for a given density predator – Predator isoclines slopes toward the right – Superimpose prey and predator isoclines ? Figure PredatorPrey Models – Superimpose prey and predator isoclines (cont.) ? One stable point emerges: the intersection of the lines ? Three general cases – Inefficient predators require high densities of prey (Figure ) Damped oscillations Prey isocline Predator isocline a) PredatorPrey Models ? Three general cases (cont.) – A moderately efficient predator leads to stable oscillations of predator and prey populations (Figure ) Stable oscillations Population density Predator equilibrium density b) PredatorPrey Models ? Three general cases (cont.) – A highly efficient predator can exploit a prey nearly down to its limiting rareness (Figure ) Increasing oscillations c) PredatorPrey Models ? All based on how efficient predator is ? Shift in isoclines – Prey starvation (shift to left) – Food enrichment (shift to right) (Figure ) K1 increases to K1* with enrichment Prey Predator Predator isocline remains unchanged “The paradox of enrichment” Prey isocline changes K1 K1* d) PredatorPrey Models – Food enrichment (shift to right) (cont.) 187。t they tell us? Discussion Question 6 ? Which do you think more likely: that predators control prey populations or that prey control predator populations? Would the answer vary according to the particular system? Give an example. Discussion Question 7 ? What shortings do you think Rosenzweig and MacArthur39。160 fold increase in red kangaroos 187。Good evidence of prey population control by predators 187。Declined as the wolf population increased until 1981 Field Studies of PredatorPrey Interactions – Moose population (cont.) 187。Small recovery in the late 1990s – Moose population 187。Peaked at 50 in 1980 187。s Isle Royale Field Studies of PredatorPrey Interactions – Moose population on Michigan39。 low at low prey densities, but increases quickly at high densities – Changes in prey consumption ? Functional response changes (Figure ) PredatorPrey Models ? Functional response changes (cont.) – Dictates how individual predators respond to prey population ? Numerical response changes – Governs how a predator population migrates into and out of areas in response to prey densities Field Studies of PredatorPrey Interactions ? Field parisons to models ? Do predators control prey populations? ? Importance of predators in controlling prey density – Kaibab deer herd ? Kaibab Plateau (Northern Arizona) Field Studies of PredatorPrey Interactions – Kaibab deer herd (cont.) ? Declared a national park around 1900 ? All big predators were removed and deer hunting was prohibited ? Estimates of 10 fold increase in deer population ? Reevaluated by Graham Caughley (1970) Field Studies of PredatorPrey Interactions ? Reevaluated by Graham Caughley (1970) (cont.) – Predator control had some impact。Carrying capacity changes 187。Ex. Wasps and some butterflies 187。ller, 1879 – Unpalatable species converge to look the same Antipredator Adaptations – Unpalatable species converge to look the same (cont.) 187。 ＊植物的自疏現(xiàn)象 ＊禾本科植物的分的產(chǎn)生和生長 ＊遺傳特性 (抗逆性 ) ＊內(nèi)分泌調(diào)節(jié) (旅鼠 ) Crowding stress 腎上腺髓質(zhì) (adrenocorticotropin) 腦下腺 (Epinephrine) 腎上腺皮質(zhì) (Corticoids) 危急反應 Alarm response Introduction ? Wolves in Yellowstone Park (Figure ) – . Fish and Wildlife Service, 1980’s – Reintroduce in Yellowstone Park and stabilize wolf populations in Minnesota and Montana – Concerns ? Cattle ranchers concerned: Decimate herd? ? Are predators tied to the health of the main prey? ? Can predators switch prey? ? Ramifications to reestablishment – Results: No major effects Introduction ? Predation – Traditional view: carnivory – Differences from herbivory ? Herbivory is nonlethal – Differences from parasitism ? In parasitism, one individual is utilized for the development of more than one parasite Introduction ? Predation (cont.) – Predatorprey associations ? Figure Intimacy Low High Parasite Parasitoids Grazer Predator Lethality High Low Antipredator Adaptations ? Aposematic or warning coloration – Advertises an unpalatable taste – Ex. Blue jays and monarch butterflies ? Caterpillar obtains poison from milkweed Antipredator Adaptations – Ex. Blue jays and monarch butterflies (cont.) ? Blue jays suffer violent vomiting from ingesting caterpillar – Ex. Tropical frogs ? Toxic skin poisons ? Figure Antipredator Adaptations ? Camouflage – Blending of anism into background color – Grasshoppers (Figure ) Antipredator Adaptations ? Camouflage (cont.) – Stick insects mimic twigs and branches – Zebra stripes: blend into grassy background ? Mimicry Antipredator Adaptations ? Mimicry (cont.) – Animals that mimic other animals ? Ex. Some hoverflies mimic wasps Mimicry – Types of mimicry ? M252。 A factor affecting population size whose intensity of action varies with density. (二 ) )Density independent factor非密度制約因素 (外界環(huán)境因素 ): having an influence on individuals that does not vary with the number of individuals per unit area in the