Losos, J.B., and D. Schluter. 2000. Analysis of an evolutionary species-area relationship. Nature 408:847-850.


    A species-area relationship exists for Anolis lizards on Caribbean islands.  Using a phylogeny, it is possible to identify whether a species has arisen in situ within an island, or whether it arrived by colonization from another island.  The existence of sister taxa on the same island suggests the former possibility--for example, the alutaceus group contains 14 species, all on Cuba.  The most parsimonious interpretation is that at least 13 speciation events have occurred on Cuba, producing these species.  By contrast, when sister taxa occur on different islands, the most likely explanation is that speciation occurred after populations became isolated on different islands, either by colonization or vicariance.

    Based on this approach, we investigated whether a relationship exists between island area and rate of speciation.  We found, first, that a threshold island area exists below which speciation rarely, if ever, occurs.  This threshold falls between Guadeloupe, which contains only 1 anole species, and Puerto Rico, which has 10.  Why speciation has not occurred on Guadeloupe, or other relatively large islands, is not clear.  The island is vegetationally and topographically complex and anoles have inhabited the island for millions of years.  Second, among those islands which have experienced in situ speciation, the rate of speciation increases with island area.  This speciation-area relationship is a potentially important complement to ecological explanations for species-area relationships.