Size Patterns in West Indian Anolis Lizards. II. Correlations with the Sizes of Particular Sympatric Species-Displacement and Convergence

Abstract

Differences in head length and snout-vent length were computed for all combinations of Anolis species taken two at a time on the Greater Antilles. There is a tendency to converge associated with structural-habitat similarity: Males of species whose range projections on a map do not overlap are significantly closer in size if structural habitats are similar than if different. There is a tendency to diverge associated with spatial overlap: Species with substantial structural habitat similarity are more different in head and snout-vent length if their ranges overlap than if allopatric. When a given species overlaps in part of its range with a second smaller species of similar structural habitat, convergence in head and snout-vent length is about as frequent as divergence; that is, the given species is as likely to increase its size as to decrease that size. Relatively large species converge significantly more often in this situation than do smaller species. However, where a given species overlaps in part of its range with a second larger species, divergence (a decrease in size) of the given species occurs much more often than convergence. If character divergence involves an increase in size, the factor of that increase is significantly less than if it involves a decrease. Ratios of head length are usually greater than 1.5 among spatially overlapping species on two species islands and are often so on the richest islands. Associations of three spatially overlapping Anolis species nearly always show the greatest head-length ratio between the two largest species.