Distribution of Vertebrates on Some Very Small Islands. I. Occurrence Sequences of Individual Species

Abstract

The geographic distribution of 76 species of lizards, resident birds and migrant birds was studied on 521 Bahamian islands. The presence and absence of each individual species on islands belonging to each of 41 archipelagos was related to 54 variables measured for each island. Occurrences of individual species of lizards and resident birds are more related to island area than are those of migrants. Lizard occurrences are best predicted by vegetation availability in height layers lower than those best predicting bird occurrences. Structural-vegetation diversity is more important in predicting lizard species occurrences than bird species occurrences. Distance variables better predict occurrences of migrant birds than those of other groups; migrant occurrences tend to be positively related to distance to a larger island; lizard occurrences tend to be negatively related to distance to a main island. Species occurrences are better predicted by island area, the more geographically inclusive the archipelago. Maximum altitude in a multivariate analysis is sometimes more important than area in predicting lizard species occurrences. An enormous number of species distributions are non-randomly related to island characteristics; the number is smaller for migrants than for resident species.