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

3. Exponential growth model can not explain the population growth here Need other equation Barnacle

4. Birth rate and death rate change with population size N dN/dt=rN r=b-d b=b0-aN d=d0+cN dN/dt=[(b0-d0)- (a+c)N]N dN/dt=(b0-d0)[1- (a+c)/(b0-d0)*N]N dN/dt=r N(1-N/K) K=(b0-d0)/(a+c) K: carrying capacity: maximum sustainable population size under prevailing environmental environment.

5. From exponential growth to logistic growth

6. Logistic population growth

7. Logistic Population Growth

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

9. A few examples

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

13. Regulation of population size by density- dependent factors

15. 11.3 Competition results when resources are limited Intraspecific competition: competition among individuals of the same species Intraspecific competition: competition among individuals of the same species Scramble competition: growth and reproduction are depressed equally across individuals in a populationScramble competition: growth and reproduction are depressed equally across individuals in a population All individuals receiving insufficient resources  local extinction All individuals receiving insufficient resources  local extinction Contest competition: some individuals claim enough resources while denying others a shareContest competition: some individuals claim enough resources while denying others a share A fraction of the population suffers. Successful competitors to sustain the population. A fraction of the population suffers. Successful competitors to sustain the population.

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) 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). Interference: direct influencing each other by preventing others to occupy a habit or access resources (birds, animals).

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. 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 Relationship of body growth and density Tadpole and white clove

18. Horseweed experiment Kyoji Yoda, plant ecologist Horseweed was planted at a very high density (100,000 seeds m-2) Density declined in several months Weight per seedling increased. Self-thinning: progressive decline in density and increase in biomass of remaining individuals in a population.

19. 11.5 Intraspecific competition can reduce reproduction Intraspecifc competition can function to reduce fecundity Intraspecifc competition can function to reduce fecundity Harp seals shrub corn

20. Growth and mortality in steelhead trout (Keeley et al.)

21. 11.6 Territoriality can function to regulate population growth Home range: the area that an animal normally use during a year 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. 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: a defended area by an animal. Territory could be part of or the same as home range.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.Use well-defined behavioral patterns: song and call, intimidation displays, attack and chase, marking with scents.

22. Territories of the grasshopper sparrow Territory is protected Territory is protected FoodFood MatingMating Nesting siteNesting site Attraction of matesAttraction of mates Avoidance of suboptimal habitatAvoidance of suboptimal habitat Needs energyNeeds energy May not be optimal strategy when resources are low May not be optimal strategy when resources are low

23. 11.7 Density-independent factors can influence population growth Factors such as temperature, precipitation and natural disasters (fire, flood and drought) are density- independent factors

24. The End

26. Modes of Competition Intraspecific: Intraspecific: Competition with members of own species.Competition with members of own species. Interspecific: Interspecific: Competition between individuals of two species - reduces fitness of both.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. 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 Prediction of growth for gray squirrel population r=0.18, K=200, N0=30