【正文】 .) ? Reduced insects due to introduction of herbicides in the 1950s was suspected ? However, smaller populations in areas where there was no control of predators by gamekeepers Field Experiments with Natural Systems – Only million shot in the mid1980s (cont.) ? Predation control increased – The number of partridges that bred successfully – The average size of the broods – Partridge populations by 75 % Field Experiments with Natural Systems ? Predators and rodents in Finland – Large scale removal of predators, April 1992 and 1995 over 23 km2 – Large increase in rodent population by June (pared to control plots) (Figure ) April June April June 3 2 1 0 3 2 1 0 Without predators With predators Mean number of rodents per sample Mean number of rodents per sample Applied Ecology ? Humans as predators whaling – Exploitation necessary – Is harvesting at any level sustainable? ? History of Antarctic whaling – Figure 1 Applied Ecology ? History of Antarctic whaling (cont.) – 1930s, blue whales primarily。Confounded in 1996 when the moose population crashed starvation Field Studies of PredatorPrey Interactions – Canada lynx and snowshoe hare ? Populations show dramatic cyclic oscillations every 9 to 11 years (Figure ) 20 40 60 80 100 120 20 40 60 80 100 120 140 160 180 200 Abundance of lynx Abundance of hares Abundance of lynx (x 1000) Abundance of hares (x 1000) 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 Field Studies of PredatorPrey Interactions – Canada lynx and snowshoe hare (cont.) ? Cycle has existed as long as records have existed (over 200 years) ? An example of intrinsically stable predatorprey relationship Introduced Predators ? Method for determining the effects of predators ? Dingo predations on kangaroos in Australia – Dingo ? Introduced species ? Largest Australian carnivore Introduced Predators – Dingo (cont.) ? Predator of imported sheep ? Eliminated from certain areas – Spectacular increases in native species 187。Increased steadily in the 1960s and 1970s 187。s Isle Royale (cont.) ? Wolffree existence until 1949. ? Durwood Allen (1958) began to track wolf and moose populations ? Trends in populations (Figure ) 60 0 10 20 30 40 50 Wolves 1955 1960 1965 1970 1975 1980 1985 1990 1995 1997 Moose Wolves Year 200 400 600 800 1000 1200 1400 1600 1800 2020 2200 2400 2600 Moose 0 Field Studies of PredatorPrey Interactions ? Trends in populations (cont.) – Wolf population 187。Predator isocline changes – “paradox enrichment” : Increases in nutrients or food destabilizes the system PredatorPrey Models ? Functional response – How an individual predator responds to prey density can affect how predators interact with prey (Figure ) I II III Number of prey eaten per predator Prey density PredatorPrey Models ? Functional response (cont.) – Three types ? Type I: Individuals consume more prey as prey density increases ? Type II: Predators can bee satiated and stop feeding, or limited by handling time. PredatorPrey Models – Three types (cont.) ? Type III: Feeding rate is similar to logistic curve。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。Good evidence of prey population control by predators 187。Small recovery in the late 1990s – Moose population 187。s Isle Royale Field Studies of PredatorPrey Interactions – Moose population on Michigan39。Carrying capacity changes 187。ller, 1879 – Unpalatable species converge to look the same Antipredator Adaptations – Unpalatable species converge to look the same (cont.) 187。 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 population. Densitydependent factor 密度制約因子 : 1. 種間因素 .食物、空間資源 ? 種內(nèi)、種間競爭 .病蟲害傳播速度 .個(gè)體成熟速度 .體質(zhì)和繁殖力、生長發(fā)育、自相殘殺、外遷 .植物結(jié)實(shí)數(shù)量 .抗逆性 在橡樹蛾的生活史裡，有不同的生活環(huán)境，不同的掠食者 ,寄生、競爭、環(huán)境壓力，在不同時(shí)期裡會有不同的死亡率。 2020 by Prentice Hall, Inc. Upper Saddle River, NJ 07458 Outline ? There are a variety of antipredator adaptations, which suggests that predation is important in nature ? Predatorprey models can explain many outes ? Field data suggests that predators have a large impact on prey populations Outline ? Experiments involving the removal or introduction of exotic predators provide good data on the effects of predators on their prey ? Field experiments involving the manipulations of native populations show predation to be a strong force Equilibrium theories of population regulation ? A. Extrinsic biotic school – 1. Food supply and population regulation – 2. Predation and population regulation – 3. Disease and population ? B. Intrinsic school – 1. Stress and territoriality – 2. Geic polymorphism hypothesis – 3. Dispersal The causes of population change key factor analysis 主導(dǎo)因子分析 (一 ) Densitydependent factor 密度制約因子 : (種內(nèi)、種間因素 )作用強(qiáng)度隨種群密度而變。llerian mimicry – Fritz M252。Mimicry ring: a group of sympatric species, often different taxa, share a mon warning pattern ? Batesian mimicry – Henry Bates, 1862 – Mimicry of unpalatable species by palatable species Antipredator Adaptati