barnacle Chthalamus stellatus . Lotka Volterra Competition Alfred J. - PowerPoint PPT Presentation

J. H. Connell, Ecology, 1961. The influence of interspecific competition and other factors on the distribution of the p f f barnacle Chthalamus stellatus .

Lotka ‐ Volterra Competition Alfred J. Lotka (1880 – 1949), Vito Volterra (1860 – 1940) Lotka ‐ Volterra models (including competition): Per capita growth L tk V lt d l (i l di titi ) P it th rate of any species depends linearly on the densities of other species in the community.     1 dN N N   1 1 2 r  1  1 N N dt dt   K K   1 1     1 dN N N   2 2 1 r  1  2 N N dt dt   K K   2 2

Isoclines are not necessarily straight lines from Gilpin & Justice, Nature , 1972

Resource competition David Tilman competition among algae in chemostats Photo credit Thomas Massie

What are “resources”? Tilman: “A resource is defined as a consumable factor for which increases in its availability lead to increased per capita reproductive rates, through at least some range of its d ti t th h t l t f it availability. … It is through the depression of resource levels caused by consumption that species compete with each other, and thus that resources may influence the structure of communities. ” Examples (for plants): Water, light (PAR), nutrients, space (for sessile plants) Temperature is not a resource (why?)

Resource competition, a la Tilman For each resource: Rate of change Resource Biotic = ‐ of resource supply consumption For each consumer: Resource ‐ Per capita rate dependent dependent = = ‐ ‐ Mortality Mortality of change reproduction

Resource competition, a la Tilman For each resource: Rate of change Resource Biotic = ‐ of resource supply consumption For each consumer: Resource ‐ Per capita rate dependent dependent = = ‐ ‐ Mortality Mortality of change reproduction