DEWLAP COLOR VARIATION AND ELECTROPHORETICALLY DETECTED SIBLING SPECIES IN A HAITIAN LIZARD, ANOLIS BREVIROSTRIS.

Abstract

Seven to thirty ecologically diverse species of the iguanid genus Anolis live on each of the four Greater Antilles. Except quite locally, these species rarely occur without congeners. Usually an individual will encounter in a single day-or at least in its lifetime-individuals of from three to as many as six or seven other species. The dewlap, an extensible fold of skin contracted against the throat when not in use, is believed to be an important character by which these highly visual animals discriminate between members of their own and other species (Rand and Williams, 1970). Males of most anoles retain the ancestral condition of a large dewlap, though it is secondarily reduced or lost in a few species. By contrast, the dewlap of females is normally small. Dewlap extension is a component of displays in many anole species, but display repertoires and functions have been analyzed in only a few. There is evidence that displays involving the dewlap are used throughout the process of mate selection, which itself is poorly understood. A female may associate with a conspecific male on the basis of his common (assertion) display, with the male so selected enjoying the status of preferred mate when the female becomes receptive (Jenssen, 1970a, 1971). In several species, the dewlap is routinely extended in the male display that immediately precedes copulation (Greenberg and Noble, 1944; Gordon, 1956; Kastle, 1963; Rand, 1967; Ruibal, 1967); and while there are display patterns unique to this final stage of courtship, the common display may be given in combination with them (Kastle, 1963; Jenssen, 1970b). Indirect evidence further points to the importance of the dewlap as an isolating mechanism. Typically the dewlap of each member of a sympatric association is distinctive. For example, in each of the eight species known or suspected to occur at La Palma, Dominican Republic, the combination of colors differs; and size and shape also vary markedly (Rand and Williams, 1970). Pairs of closely related species often have widely divergent dewlap colors. Although geographic variation in dewlap color is not rare, intraspecific differences are generally less than those between sympatric species. However, two common Hispaniolan species, Anolis distichus and A. brevirostris, deviate in showing complex and striking geographic variation in dewlap color. Both species are relatively small and thick-bodied, differing in body color and pattern but not consistently in any scale character (Schwartz, 1968). In the lowlands of Hispaniola, A. distichus occupies mesic habitats, whereas A. brevirostris occurs in those that are more arid and therefore has a notably irregular range (Fig. 1). Even though these species do not overlap broadly, they do make contact: both have been found on the same tree in many areas. Major variation in dewlap color has been described and figured for A. distichus (Schwartz, 1968) and recorded for A. brevirostris (field notes of J. D. Lazell, A. S. Rand, A. Schwartz, and E. E. Williams). To investigate the significance of such variation, we decided to describe it in greater detail across a series of Haitian populations of A. brevirostris and to determine the relationships of those same