BIOL 4120: Principles of Ecology Lecture 11: Intraspecific Population Regulation

1. BIOL 4120: Principles of Ecology Lecture 11: Intraspecific Population Regulation Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

2. 11.1 Logistic Population Growth dovedove

3. barnaclebarnacle

4. Birth rate and death rate change with population size N The reason is that exponential growth assume no resource limitation on birth rate and constant death rate. For exponential population growth model, we assume that r=b-d, this r will not change with population size N. Actually, the birth rate and death rate will change as population size increases. We assume b=b0 and d=d0 and will not change with N, but in reality, b and d may change with N.The reason is that exponential growth assume no resource limitation on birth rate and constant death rate. For exponential population growth model, we assume that r=b-d, this r will not change with population size N. Actually, the birth rate and death rate will change as population size increases. We assume b=b0 and d=d0 and will not change with N, but in reality, b and d may change with N.

5. From exponential growth to logistic growth R is the parameter that determining the shape of the growth form k/2: inflection point K-strategist and r-strategist R is the parameter that determining the shape of the growth form k/2: inflection point K-strategist and r-strategist

6. Logistic population growth

7. Logistic Population Growth http://www.pbs.org/wgbh/nova/worldbalance/numb-flash.html Growth model: Excelhttp://www.pbs.org/wgbh/nova/worldbalance/numb-flash.html Growth model: Excel

8. Logistic Population Growth As resources are depleted, population growth rate slows and eventually stops: logistic population growth. Sigmoid (S-shaped) population growth curve. Carrying capacity (K) is the number of individuals of a population the environment can support. (r) is per capita increase rate.

11. K-strategist and r-strategist K-strategist and r-strategist

12. 11.2 Population regulation involves density dependence Environment limits population growth by altering birth and death rates. Density-dependent factors E.g., Disease, Resource competition They influence a population in proportion to its size Resulted in slowing the rate of increase Density-independent factors E.g., Natural disasters Influence population without regard to the # of individuals or if the proportion of individuals affected is the same at any density

13. Environmental factors could either increase d, decrease b or both, as population increase (density-dependent). Fig a. E only inlfucence d, not b. As N increases, d increases, b is constant, r changes. When N is smaller than K, b>d, population will increases; b=d, r=0, popu will reach K and maintain at carrying capacity. If N>K, d>b, r<0, population decreases, will reach K. Negative feedback at K Environmental factors could either increase d, decrease b or both, as population increase (density-dependent). Fig a. E only inlfucence d, not b. As N increases, d increases, b is constant, r changes. When N is smaller than K, b>d, population will increases; b=d, r=0, popu will reach K and maintain at carrying capacity. If N>K, d>b, r<0, population decreases, will reach K. Negative feedback at K

14. Under conditions of Allee effects, below some min population, d increases, b decreases or both. Positive feedback at A, lead to extinction. unstable: if slightly lower than A, move to extinction, otherwise, move to K Negative feedback at K Under conditions of Allee effects, below some min population, d increases, b decreases or both. Positive feedback at A, lead to extinction. unstable: if slightly lower than A, move to extinction, otherwise, move to K Negative feedback at K

15. 11.3 Competition results when resources are limited Intraspecific competition: competition among individuals of the same species Scramble competition: growth and reproduction are depressed equally across individuals in a population All individuals receiving insufficient resources ? local extinction Contest competition: some individuals claim enough resources while denying others a share A fraction of the population suffers. Successful competitors to sustain the population. As long as availablility of resources does not impede the ability of individuals to survive, grow, and reproduce, no competition exists. When recouses are insufficient, competition occurs. Another point of view of competition: explo, and inter.As long as availablility of resources does not impede the ability of individuals to survive, grow, and reproduce, no competition exists. When recouses are insufficient, competition occurs. Another point of view of competition: explo, and inter.

16. Competition results when resources are limited Exploitation: indirectly influencing each other by consuming the same resources (eat same grass by zebras , compete for water uptake by trees, indirectly) Interference: direct influencing each other by preventing others to occupy a habit or access resources (birds, animals). Another point of view of competition: explo, and inter.Another point of view of competition: explo, and inter.

17. 11.4 Intraspecific competition affects growth and development Intraspecific competition is usually density-dependent. It increases gradually, at first affects growth and development, then individual survival and reproduction. Relationship of body growth and density Plant competition experiment (how to construct this curve?) Numbers are density of tadpole Plant competition experiment (how to construct this curve?) Numbers are density of tadpole

18. Horseweed experiment

19. 11.5 Intraspecific competition can reduce reproduction Intraspecifc competition can function to reduce fecundity Whelp: produce baby dog, seal Whelp: produce baby dog, seal

20. E. Keeley (University of British Columbia) examined density-dependent growth and mortality in steelhead trout (Oncorhynchus mykiss) populations The results indicate a pattern of decreasing growth and increasing mortality with increasing levels of per capita food competition The same patterns were seen, whether resulting from An increase in population density for a given level of food abundance E. Keeley (University of British Columbia) examined density-dependent growth and mortality in steelhead trout (Oncorhynchus mykiss) populations The results indicate a pattern of decreasing growth and increasing mortality with increasing levels of per capita food competition The same patterns were seen, whether resulting from An increase in population density for a given level of food abundance

21. 11.6 Territoriality can function to regulate population growth Home range: the area that an animal normally use during a year Home range varies with the available of food resources, model of food gathering, body size and metabolic needs. Territory: a defended area by an animal. Territory could be part of or the same as home range. Use well-defined behavioral patterns: song and call, intimidation displays, attack and chase, marking with scents. For animals, another factor influences population growth is home range and territoryFor animals, another factor influences population growth is home range and territory

22. Territories of the grasshopper sparrow Under what conditions can territoriality function as a mechanism of population regulation? If all pairs that settle on an area get a territory, territoriality only influences the spatial distribution within the population. But if territory size has a low limit, then individuals that failed to find one have to leave. Under what conditions can territoriality function as a mechanism of population regulation? If all pairs that settle on an area get a territory, territoriality only influences the spatial distribution within the population. But if territory size has a low limit, then individuals that failed to find one have to leave.

23. 11.7 Density-independent factors can influence population growth

24. The End

25. Figure 11.15Figure 11.15

26. Modes of Competition Intraspecific: Competition with members of own species. Interspecific: Competition between individuals of two species - reduces fitness of both.

27. Intrinsic Rates of Increase On average, small organisms have higher rates of per capita increase and more variable populations than large organisms.

28. Compare of logistic with exponential growth curves