Theory of Island Biogeography Notes Why do more

Theory of Island Biogeography Notes

Why do more species of birds occur on the island of New Guinea than on the island of Bali?

Why do more species of birds occur on the island of New Guinea than on the island of Bali? • New Guinea has more than fifty times the area of Bali, and numbers of species ordinarily increase with available space.

Why do many more species of birds occur on the island of New Guinea than on the island of Bali? • This does not, however, explain why the Society Islands (Tahiti, Moorea, Bora, etc. ), which collectively have about the same area as the islands of the Louisiade Archipelago off New Guinea, play host to fewer species • Or why the Hawaiian Islands, ten times the area of the Louisiades, also have fewer native birds How can islands of the same size differ in their amount of biodiversity?

Equilibrium Theory of Island Biogeography • E. O. Wilson & Robert Mac. Arthur • Theory that explains how species come to be distributed among oceanic islands

Equilibrium Theory of Island Biogeography • 1. The farther away an island is from a continent→ the fewer species tend to find and colonize it. • 2. Larger islands have higher immigration rates • 3. Larger islands have lower extirpation/extinction rates

Theory of Island Biogeography • The number of species found on an undisturbed island is determined by immigration and extirpation/extinction – Immigration is affected by the distance an island is from a mainland/island • The rate of extinction once a species manages to colonize an island is affected by island size – Larger islands contain larger habitat areas and opportunities for more different varieties of habitat. Larger habitat size reduces the probability of extirpation/extinction due to chance events.

This theory also applies to “habitat islands”

Sum it all up… • Increased biodiversity in islands that are: – Closer to land – Larger in size – Closer to equator • Climate: Stable weather • Longer growing season – Higher NPP (energy) • Supports more organisms – More habitats available