Chap. 7 Predation, grazing and disease 鄭先祐 (Ayo) 國立臺南大學 環境與生態學院 生物科技學系 生態學 (2008) Essentials of Ecology 3 rd. Ed.

2 Predation, grazing and disease 7.1 introduction 7.1 introduction 7.2 Prey fitness and abundance 7.2 Prey fitness and abundance 7.3 the subtleties ( 微妙之處 ) of predation 7.3 the subtleties ( 微妙之處 ) of predation 7.4 predator behavior: foraging and transmission 7.4 predator behavior: foraging and transmission 7.5 population dynamics of predation 7.5 population dynamics of predation 7.6 predation and community structure 7.6 predation and community structure

3 7.1 Introduction Three main types of predator Three main types of predator ‘true’ Predators ‘true’ Predators Grazers Grazers Parasites Parasites

4 7.2 prey fitness and abundance The fundamental similarity between predators, grazers and parasites is that each, in obtaining the resources it needs, reduces either the fecundity or the chances of survival of individual prey and may therefore reduce prey abundance. The fundamental similarity between predators, grazers and parasites is that each, in obtaining the resources it needs, reduces either the fecundity or the chances of survival of individual prey and may therefore reduce prey abundance. When the sand-dune willow was grazed by a flea beetle in two separate years (1990 and 1991) the reduction in the growth rate of the willow was marked in both years (Fig. 7.1), but the consequences were rather different. When the sand-dune willow was grazed by a flea beetle in two separate years (1990 and 1991) the reduction in the growth rate of the willow was marked in both years (Fig. 7.1), but the consequences were rather different.

5 Fig.7.1 Relative growth rates of a number of different clones of the sand-dune willow in 1990 and Fig.7.1 Relative growth rates of a number of different clones of the sand-dune willow in 1990 and 1991.

6 7.2 prey fitness and abundance Only in 1991 were the plants also subject to a severe shortage of water. Only in 1991 were the plants also subject to a severe shortage of water. Thus it was only in 1991 that reduced growth rate was translated into plant mortality: Thus it was only in 1991 that reduced growth rate was translated into plant mortality: 80% of the plants died in the high grazing treatment, 80% of the plants died in the high grazing treatment, 40% died in the low grazing treatment, 40% died in the low grazing treatment, But none of the ungrazed control plants died. But none of the ungrazed control plants died.

7 Fig. 7.2 The proportion of males of male pled flycatchers infected with Trypanosoma (blood parasites) amongst groups of migrants arriving in Finland at different times. Fig. 7.2 The proportion of males of male pled flycatchers infected with Trypanosoma (blood parasites) amongst groups of migrants arriving in Finland at different times.

8 Fig. 7.3 Long-term population dynamics in laboratory population cages of a host (Indian meal moth), with and with (a) or without (b) its parasitoid (parasitoid wasp). Fig. 7.3 Long-term population dynamics in laboratory population cages of a host (Indian meal moth), with and with (a) or without (b) its parasitoid (parasitoid wasp).

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the subtleties of predation interactions with other factors interactions with other factors compensation and defense by individual prey compensation and defense by individual prey from individual prey to prey populations from individual prey to prey populations

interactions with other factors Californian salt marsh, where the parasitic plant, dodder (Cuscuta salina) attacks a number of plants including Salicornia (Fig.7.4). Californian salt marsh, where the parasitic plant, dodder (Cuscuta salina) attacks a number of plants including Salicornia (Fig.7.4). Salicornia tends to be the strongest competitor in the marsh, but it is also the preferred host of dodder. Salicornia tends to be the strongest competitor in the marsh, but it is also the preferred host of dodder. The distribution can therefore only be understood as a result of the interaction between competition and parasitism (Fig. 7.4) The distribution can therefore only be understood as a result of the interaction between competition and parasitism (Fig. 7.4) Salicornia virginica→

12 Fig. 7.4 The effect of dodder (Cuscula salina) on competition between Salicornia and other species in a southern Californian salt marsh. Fig. 7.4 The effect of dodder (Cuscula salina) on competition between Salicornia and other species in a southern Californian salt marsh.

13 Fig. 7.4(b) over time, Salicornia decreased and Arthrocnemum increased in plots infected with dodder. (c) Dodder suppress Salicornia and favor Limonium and Frankenia. Fig. 7.4(b) over time, Salicornia decreased and Arthrocnemum increased in plots infected with dodder. (c) Dodder suppress Salicornia and favor Limonium and Frankenia.

14 Fig. 7.5 infection with a nematode worm parasite makes red grouse more susceptible to predation. Fig. 7.5 infection with a nematode worm parasite makes red grouse more susceptible to predation. (a)Worm burdens of birds that are shot for ‘sport’, which may be taken as a representative sample of the whole population. (b)Worm burdens of those found killed by predators.

compensation and defense by individual prey Compensatory plant responses Compensatory plant responses Defensive plant responses (Fig. 7.7) Defensive plant responses (Fig. 7.7) Fig 7.6 compensatory plant responses

16 Fig. 7.7 (a) Phlorotannin content of Ascophyllum nodosum plants after exposure to simulated herbivory or grazing by the snail Littorina obtusata. Fig. 7.7 (a) Phlorotannin content of Ascophyllum nodosum plants after exposure to simulated herbivory or grazing by the snail Littorina obtusata.

17 Fig. 7.8 (a) percentage leaf area consumed by chewing herbivores and (b) number of aphids per plant, measured on two dates in three field treatments. Fig. 7.8 (a) percentage leaf area consumed by chewing herbivores and (b) number of aphids per plant, measured on two dates in three field treatments. Overall control, Overall control, damage control (tissue removed by scissors) damage control (tissue removed by scissors) Induced (caused by grazing of caterpillars. Induced (caused by grazing of caterpillars.

18 Fig7.8c fitness of plants in the three treatments. Fig7.8c fitness of plants in the three treatments.

from individual prey to prey populations Compensatory reactions amongst surviving prey (Fig. 7.9) Compensatory reactions amongst surviving prey (Fig. 7.9) But compensation is often imperfect (Fig. 7.10) But compensation is often imperfect (Fig. 7.10) Predators often attack the weakest and most vulnerable (Fig. 7.11) Predators often attack the weakest and most vulnerable (Fig. 7.11)

20 Fig. 7.9 Fig. 7.9 Trajectories of numbers of grasshoppers surviving for fertilizer and predation treatment combination in a field experiment. Fertilizer, predation 影響顯著 No fertilizer, predation 影響不顯著

21 Fig when Douglas fir seeds are protected from vertebrate predation by screens. Fig when Douglas fir seeds are protected from vertebrate predation by screens.

22 Fig (a) the proportions of different age classes of Thomson’s gazelles in cheetah and wild dog kills is quite different from their proportions in the population as a whole. Fig (a) the proportions of different age classes of Thomson’s gazelles in cheetah and wild dog kills is quite different from their proportions in the population as a whole.

23 Fig (b) age influence the probability for Thomson’s gazelles of escaping when chased by cheetahs Fig (b) age influence the probability for Thomson’s gazelles of escaping when chased by cheetahs (c) when prey zigzag to escape chasing cheetahs, prey age influences the mean distance lost by the cheetahs. (c) when prey zigzag to escape chasing cheetahs, prey age influences the mean distance lost by the cheetahs.

predator behavior: foraging and transmission Active predators Sit-and -wait Direct parasiteTransmission

foraging behavior Behavioral ecology Behavioral ecology The evolutionary, optimal foraging approach The evolutionary, optimal foraging approach Applying the optimal foraging approach to a range of foraging behaviors Applying the optimal foraging approach to a range of foraging behaviors Predictions of the optimal diet model Predictions of the optimal diet model

26 Fig Fig The types of foraging decisions considered by optimal foraging theory The types of foraging decisions considered by optimal foraging theory (a) choosing between habitats (a) choosing between habitats (b) the conflict between increasing input and avoiding predation. (b) the conflict between increasing input and avoiding predation. choosing between habitats the conflict between increasing input and avoiding predation.

27 (c) patch stay-time decisions (c) patch stay-time decisions (d) the ideal free decision- the conflict between patch quality and competitor density (d) the ideal free decision- the conflict between patch quality and competitor density (e) optimal diets (e) optimal diets patch stay-time decisions patch stay-time decisions optimal diets patch quality and competitor density patch quality and competitor density

population dynamics of predation underlying dynamics of predator-prey interactions: a tendency to cycle (Fig. 7.15) underlying dynamics of predator-prey interactions: a tendency to cycle (Fig. 7.15) predator-prey cycles in practice (Fig. 7.18, 19) predator-prey cycles in practice (Fig. 7.18, 19) disease dynamics and cycles (Fig. 7.20) disease dynamics and cycles (Fig. 7.20) crowding (Fig. 7.21) crowding (Fig. 7.21) predators and prey in patches (Fig. 7.22, predators and prey in patches (Fig. 7.22, 23

underlying dynamics of predator-prey interactions: a tendency to cycle Fig the underlying tendency for predators and prey to display coupled oscillation in abundance Fig the underlying tendency for predators and prey to display coupled oscillation in abundance

predator-prey cycles in practice Fig 7.18a parthenogenetic female rotifers and unicellular green algae in laboratory cultures. Fig 7.18a parthenogenetic female rotifers and unicellular green algae in laboratory cultures.

31 Fig. 7.18b the snowshoe hare and the Canada lynx. Fig. 7.18b the snowshoe hare and the Canada lynx.

32 Fig. 7.19a the main species and groups of species in the boreal forest community of North America, with trophic interactions. Fig. 7.19a the main species and groups of species in the boreal forest community of North America, with trophic interactions.

33 Fig Fig. 7.19

disease dynamics and cycles Fig (a) reported cases of measles in England and Wales from 1948 to 1968, prior to the introduction of mass vaccination Fig (a) reported cases of measles in England and Wales from 1948 to 1968, prior to the introduction of mass vaccination (b) reported cases of pertussis (whooping cough) in England and Wales from 1968 to Mass vaccination was introduced in 1956 (b) reported cases of pertussis (whooping cough) in England and Wales from 1968 to Mass vaccination was introduced in 1956

crowding Fig host immune responses are necessary for density dependence in infections of the rat with the nematode. Survivorship is independent of initial doses in mutant rats without an immune response. Fig host immune responses are necessary for density dependence in infections of the rat with the nematode. Survivorship is independent of initial doses in mutant rats without an immune response.

predators and prey in patches Dispersal and asynchrony dampen cycles Dispersal and asynchrony dampen cycles Stabilizing metapopulation effects in Huflaker’s mites (Fig. 7.22) and in starfish and mussels. Stabilizing metapopulation effects in Huflaker’s mites (Fig. 7.22) and in starfish and mussels.

37 Fig predator-prey interactions between the mite Eolentranychus sexmaculatus and its predator, the mite Typhlodromus occidentalis. Fig predator-prey interactions between the mite Eolentranychus sexmaculatus and its predator, the mite Typhlodromus occidentalis. (a) Population fluctuations of Eotetranychus without its predator. (a) Population fluctuations of Eotetranychus without its predator.

38 Fig. 7.22b a single oscillation of the predator and prey in a simple system. Fig. 7.22b a single oscillation of the predator and prey in a simple system.

39 Fig. 7.22c sustained oscillations in a more complex system. Fig. 7.22c sustained oscillations in a more complex system.

40 Fig a metapopulation structure can increase the persistence of predator-prey interactions. Fig a metapopulation structure can increase the persistence of predator-prey interactions. (a) the parasitoid attacking its bruchid beetle ( 甲蟲 ) host lived on beans either in small single cells or in combinations of cells. (a) the parasitoid attacking its bruchid beetle ( 甲蟲 ) host lived on beans either in small single cells or in combinations of cells. (b) The predatory ciliate( 纖毛蟲 ) feeding on the bacterivorous ciliate in bottles of various volumes. (b) The predatory ciliate( 纖毛蟲 ) feeding on the bacterivorous ciliate in bottles of various volumes.

predation and community structure Predator-mediated coexistence: predation as an interrupter of competitive exclusion Predator-mediated coexistence: predation as an interrupter of competitive exclusion For example, pigmy owls occurred on only four of the islands. For example, pigmy owls occurred on only four of the islands. The five islands without the predatory owl were home to only one species, the coal tit ( 山雀 ) The five islands without the predatory owl were home to only one species, the coal tit ( 山雀 ) However, in the presence of the owl, the coal tit was always joined by two larger tit species. However, in the presence of the owl, the coal tit was always joined by two larger tit species.

42 Fig mean species richness of pasture vegetation in plots subjected to different levels of cattle grazing in two sites in the Ethiopian highlands. Fig mean species richness of pasture vegetation in plots subjected to different levels of cattle grazing in two sites in the Ethiopian highlands.

43 Questions 動物的掠食行為，必然是「最佳策略」嗎？ 為何是？為何不是？ 動物的掠食行為，必然是「最佳策略」嗎？ 為何是？為何不是？ 按「本利分析」結果的策略，就是「最佳 策略」嗎？ 按「本利分析」結果的策略，就是「最佳 策略」嗎？ 請按生態與演化的觀點，扼要討論。 請按生態與演化的觀點，扼要討論。

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