Question 2. Consider the following figure representing the theoretical relations

Question

Question 2. Consider the following figure representing the theoretical relationships between patch area (size) and isolation (distance from one another) and the equilibrium proportion of occupied habitat patches in a metapopulation: 0.25 0.20 0.15 0.1? 0.05 ?? ?? 0 0.20.4 0.6 0.81.0 What do the lines labeled C and D on the graph represent and how do the patches modeled by each differ, specifically? What is the equilibrium proportion of occupied patches predicted for a metapopulation with large patches located relatively far from one another? Explain.

Explanation / Answer

In this graph X-axis is proportion of patches occupied and Y-axis is rate of extinction or colonization.

Here line labeled C represents small population extinction where as D represents large population extinction. Some subpopulation can go extinct, but the metapopulation continues and can recolonize empty patches.This concept is usually applied in Island Biogeography, a subset of metapopulation theory. When an island is close to its source of species,both the rate of colonization and the rate of extinction are affected. Colonizaion is affected by the proximity of the mainland.The rescue effect is a reduction in the extinction rate because a population on a island is re-colonized from the mainland and the rescue effect comes from the entery of new members into a population already established on the island and this will increase the population size and decrease the probability that the population will go extinct.

Metapopulation is stable through constant extinction-recolonization events.An equilibrium is reached which balances local extinction and recolonization.Patches can change on many ways.Some are high quality while others may be of lower quality.Some may be large and some may be isolated.We can find how these changes affect the metapopulation. There are two factors: Patch size and patch isolation.

Large patches should lead to large population.Large local populations should have a smaller chance of extinction due to demographic stochasticity.This might be specific reason for extinction.Large populations would be more likely to have individuals resistant to a disease.Large population may exceed the ability of a predator to drive the local population to extinction.Since extinction rate is a local phenomenon,isolation will not affect metapopulation.Greater distance between populations will affect the colonization rate by making it more difficult to find unoccupied patches.

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