Animation 41.2 Island Biogeography in the Florida Keys

INTRODUCTION

On a global scale, the distribution and diversity of organisms—the patterns of biogeography—vary among the different biomes, from continent to continent, and with latitude. On a smaller scale, other factors influence species diversity. Small islands tend to have fewer species than large islands, and islands close to a mainland (a species pool) tend to have more species than islands far away. The theory of island biogeography relates the size of an island and its distance from a mainland with the number of species an island maintains. The accompanying animation describes this theory as well as an experiment that tests it using mangrove islands in the Florida Keys.

Video titled: Animation 41.2 Island Biogeography in the Florida Keys

Transcript Area

Textbook Reference: Key Concept 41.4 Diversity Patterns Provide Clues to What Determines Diversity, p. 1021

CONCLUSION

According to the theory of island biogeography, any particular island or isolated patch of suitable habitat (habitat island) will maintain a certain number of species, known as the equilibrium number. The theory is based on two processes: the colonization of new species on an island and the extinction of species already present on that island. The equilibrium number is a balance between these two processes.

In turn, two factors influence colonization and extinction rates: the size of the island and the distance of the island from the species pool (the source of arrivals). Smaller islands have fewer resources and greater potential for competition. Smaller islands therefore have higher extinction rates. Islands farther from the species pool will have lower colonization rates. In this way, smaller and farther islands typically have lower equilibrium numbers than larger and closer islands.

The theory of island biogeography has important applications for the conservation of endangered species. As habitat islands decrease in size because of human encroachment, more and more species become vulnerable to population declines, especially those that require large areas in order to live and breed successfully.

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