Competition 1 Definition a A resource mediated ecological interaction in which resource use reduces the reproduction of competitors A negative negative ecological interaction Common resource usage Resources are limited Resource use leaves less for self and others Resource defense entails costs 2 Types of competition a b Intraspecific competition competition among conspecifics that is within species competition Interspecific competiton between species competition implies existence of within species competition intraspecific c Resource competition exploitative competition simple usage leaves less for others Interference competition resources are defended chemically or physically d EX allelopathy black walnut and juglone EX territories song sparrows EX any other aggressive defense behaviors to limit access by other individuals 3 Intraspecific competition a Logistic model Modification of exponential model The only new thing added o Intraspecific competition o dN dt rmaxN k n k where k is the carrying capacity of the environment model plateaus at k b the meaning of k k the maximum number of individuals an environment can stably support notice competition is dealt with indirectly by reference to population size resource base can stably support o problem black box of k c model assumptions stable age distribution density is properly measured relationship between density and rate of increase is linear o dN dt rmaxN k n k o 1 N dN dt rmax rmax N k o y mx b o slope rmaxN k o y int rmax o x int k increase in density is translated instantaneously into decrease in per capita growth rates no time lag o time lags are common in nature o not a realistic assumption time lag causes oscillation of population over time dN dt rmax N k Nt x k where x is the time lag at k resources are replaced exactly as used o otherwise populations would become extinct d logistic growth as a form of density dependent growth as density increases per capita rates decrease o negative density dependence note that there is another form of density dependent growth o positive density dependence EX Kirtlands warbler 1980s o Population of singing males below 200 o Singing rate decreases after they ve mated o Started singing in May through August o Allee effect o Could results in positive density dependence o Problems habitat destruction and brown headed cowbird e Model assessment Strong evidence for time lags and s shaped curves in nature