1. Intraspecific Competition “competition is an interaction between individuals, brought about by a shared requirement for a resource in limited supply, and leading to a reduction in the survivorship, growth and/or reproduction of the competing individuals concerned” Begon, et al. Chapter 6

2. Two types of competition Scramble (exploitative) competition *no direct interaction Contest (direct or interference) competition *some type of confrontation

3. Four characteristics of intraspecific competition The ultimate effect: decreased contribution of individuals to the next generations The resource must be in limited supply. Competing individuals are all essentially equivalent. The effect on any individual increases with increasing number of competitors

4. Density dependent mortality a=density independent; b=undercompensating density dependance; c=overcompensating density dependent

5. Exactly compensating density- dependent mortality

6. Mortality/fecundity equilibrium Reality means there is a broader range in which an equilibrium can be found

7. Population size and mortality “Pure competition”

8. Law of Constant Final Yield At low densities yield increases with density Eventually yield becomes independent of density L, M, N = nutrient levels Total yield Root wt.Shoot wt. Carrot Density and Yield

9. Timing and Size Plants emerging later grow less than predicted by average wt. gain/day Dactylis

10. Asymmetric Competition Density & time of emergence both play a role Flax

11. Results of Intraspecific competition Stress Dispersal Social interactions *dominance *territoriality

12. Territories Type of territory *general - breaks down after breeding season *nesting - (feeding is done elsewhere) *food resource Means of “defending” *Sound *Visual * Scent marking

13. Example: Red Grouse Three social classes *territorial cocks with hens *nonterritorial surplus birds - on periphery *nonterritorial transient birds Fall to Spring - territories defended *By late winter, all surplus birds removed *# & size of territories determined by amount of heather & N content of foliage

14. Red grouse breeding & survival

15. When is defense profitable? When competition exists When enough resources exist When costs do not outweigh benefits

16. Convict Cichlid Fish As territory size increases: *Chase rate *Growth rate

17. Territory size vs. animal size