Species Recognition, Dewlap Function and Faunal Size

AMER., ZOOL., 17:261-270 (1977). Species Recognition, Dewlap Function and Faunal Size ERNEST E. WILLIAMS Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138 AND A. STANLEY RAND SYNOPSIS Although having a number of functions in reproductive, territorial and aggressive behavior, Anolis dewlaps are only one means of intraspecific signaling and they are always present in small anole faunas (e.g., those of one or two species islands) but here, in contrast to the situation in large faunas, their color and pattern appear usually very similar and appear to be unimportant for species (or population) recognition. The latter function is then performed by such characteristics as adult size and body color and pattern. Where, however, numerous species abut or overlap, dewlap color and pattern tend to be diverse and diagnostic (particularly between overlapping forms). Even here, however, adult size, body shape and body color often redundantly reinforce the species and population recognition function of even marked dewlap difference. In certain cases in complex faunas, size and/or body pattern substitute for the species recognition function of reduced or absent dewlaps. In Rand and Williams (1970) we argued that species recognition in anoline lizards is not based on a single sign stimulus or releaser but on a complex of stimuli, redundant to each other, which separately and in various combinations identify the display animal. Because natural selection insists that mates be recognizable under a variety of conditions, we have argued that selection must favor a system in which species identity is encoded redundantly. In the specific case analyzed by us in 1970—species recognition in the eight species sympatric at a single locality, La Paltna, on the Greater Antillean island of Hispaniola—we found that each of the eight species differed from the rest in several (average 2-54) characteristics of the dewlap. Thus the dewlap alone sufficed to separate these eight species. This redundant use of dewlap characteristics in species recognition is also largely true in complex anole faunas of Cuba, such as the Camaguey fauna studied by Ruibal (1961a) and by Ruibal and Williams (1961a, b). Species identity in anoles, however, can be encoded redundantly in more ways than by dewlap color and size. Even in the Cuban fauna dewlap color and size by themselves will not adequately distinguish the eleven species of Camaguey (Table 1). In three species, A. equestris, A. allisoni and A porcatus, dewlaps are similar in size (large relative to body size) and color (pink or pale pink), while in two others, A. angusticeps and A. isolepis, the dewlaps differ only slightly in color ("apricot" and "peach"). In these Cuban examples adult male size or body color and pattern or both are very different. These then are two additional ways in which species identity is encoded in anoles. Climatic niche and perch site are also important, since these provide part of the context in which species recognition occurs. (Body shape is adapted to perch site and thus correlates with the latter.) Thanks are due to David Crews, Neil Greenberg The important empirical observation is and William Haas for constructive comment. This research was supported by NSF grant GB 3773IX that species similar in dewlaps differ in some or all of these other characteristics. and previous grants to E. E. Williams. 261 Smithsonian Tropical Research Institute, Balboa, Canal Zone NO NO CAMAGUEY, CUBA Species equestris allisoni porcatus angusticeps isolepis argillaceus loysiana lucius hovwlechis allogus sagrei a Dewlap color very pale pink to almost white reddish or mauve reddish or mauve peach apricot yellow yellow, orange-yellow or red tan to pink tan to pale orange red yellowish at base with white margin and 2-3 gray stripes grey or while yellow to apricot with 3-4 reddish stripes and white margin bright red, dark red or brownish yellow Body color bottle green with skin between scales white green with head and thorax blue grey with light and dark reticulation greyish bright green greyish with reticular and longitudinal markings greyish with reticular markings greenish blue with nuchal chevrons light tan with horizontal stripes and 4 dark chevrons reddish brown with yellow reticulations tan brown Size (maximum snout-vent length) Ecomorphb Microclimate 181 crown giant shade 91 66 trunk crown trunk crown sun 52 46 shade 48 twig twig trunk 42 trunk sun shade sun sun 70 crevice shade 58 trunk ground half shade 62 trunk ground shade 60 trunk ground sun Data from Ruibal and Williams (1961a and*), Ruibal (1964) and Schwartz and Garrido (1972). b Ecomorphs (Williams, 1972) differ characteristically in body shape, size, microhabitat and often in color. They are convergent phenotypes adapted to the specific stations in the vegetation (trunk-crown, trunk-ground, bush-grass) that they usually inhabit. TABLE 1. Dewlaps m local faunas (Greater Antilles)." W 73 X E »j w r > > 6 > > r X JO > o 263 SPECIES RECOGNITION, DEWLAPS AND FALNAL SIZE Yellow to yellow-orange are common dewlap colors also on other small (one to two species) islands in the Caribbean. Red -a ^ c c c .30 p I p "J b b So 5 Jt A A 3 c c c O 3 3 £ Z 3 bo c 2 1 2 Q 5 j£ •3 S ,. bo c 3 v >. S « u j, o a bo bo^J •a w re §| So bo bo bo= -^ c c c c T ; ft- 5 o S S s. lltl 1 In faunas smaller and simpler than those of Cuba and Hispaniola, dewlaps quite often are of similar size and color. A comparison of dewlap colors and sizes at Mona on the Liguanea Plain in Jamaica shows that A. garmani, A. grahami and A. opalinus, all occurring in tree crowns, all have bright orange dewlaps (Table 2). (These differ radically in size.) At El Verde Luquillo Mt., Puerto Rico,/4. evermanni (an anole of the tree crowns) and krugi (an anole living in bushes or grasses) have orange dewlaps and the dewlap of A. gundlachi (a trunk-ground anole living in deep shade below A. evermanni) is dull orange (Table 3). (These are separated by perch site and correlated body shape.) In the still smaller faunas of the Lesser Antilles (only one or two anole species per island), the similarity in dewlaps within and between islands is still more striking. One set of colors—yellow to yellow-orange, darker or lighter—occurs almost throughout both on the one and two species islands (Tables 4 and 5). Extreme variants are whitish or grey or with some hint of green. The minor variations, however, only emphasize the general regularity of dewlap color in the Lesser Antilles, which contrasts markedly with the very striking body color and pattern differences between and within Lesser Antillean species. Thus A. marmoratus on Guadeloupe has a series of races all with very similar dewlaps, in one of which males have an apple green body and a blue-grey head with brilliant orange marbling, while in another males are plain green in ground color but ant (...truncated)