Lack of Convergence in Aquatic Anolis Lizards

Abstract

Abstract. Why convergent evolution occurs among some species occupying similar habitats but not among others is a question that has received surprisingly little attention. Caribbean Anolis lizards, known for their extensive convergent evolution among islands in the Greater Antilles, are an appropriate group with which to address this question. Despite the well-documented pattern of between-island convergence, some Greater Antillean anoles are not obviously part of the convergence syndrome. One example involves aquatic anoles-species that are found near to and readily enter streams-which have evolved independently twice in the Caribbean and also twice on mainland Central America. Despite being found in similar habitats, no previous study has investigated whether aquatic anoles represent yet another case of morphological convergence. We tested this hypothesis by collecting morphological data for seven aquatic anole species and 29 species from the six convergent types of Greater Antillean habitat specialists. We failed to find evidence for morphological convergence: the two Caribbean aquatic species are greatly dissimilar to each other and to the Central American species, which, however, may be convergent upon each other. We suggest two possible reasons for this lack of convergence in an otherwise highly convergent system: either there is more than one habitat type occupied by anoles in the proximity of water, or there is more than one way to adapt to a single aquatic habitat. We estimate that almost all of the 113 species of Greater Antillean anoles occupy habitats that are also used by distantly related species, but only 15% of these species are not morphologically similar to their distantly related ecological counterparts. Comparative data from other taxa would help enlighten the question of why the extent of convergence is so great in some lineages and not in others.

What does convergent evolution mean? The interpretation of convergence and its implications in the search for limits to evolution

“…This is not just a technical quibble-it has been shown that under certain conditions, the majority of evolving taxa end up more similar to some distant relative to their own sister taxa for at least some traits [27]. Because the number of possible comparisons among taxa is astronomical and inevitably much larger than the number of known instances of convergent evolution, and equivalent lists of non-convergent taxa are unlikely to become available (due to lack of attention or publication bias, though see [66,67] for excellent examples of such studies), evolutionary null models for large-scale questions are required to establish that convergence is surprisingly ubiquitous.…”

A phylogenetic analysis of sex‐specific evolution of ecological morphology inLiolaemuslizards

“…The convergent evolution of ecologically relevant morphological traits (i.e., those targeted by natural selection) between phylogenetically unrelated species exploiting similar environments has often been regarded as evidence of adaptation (Grant 1986;Harvey and Pagel 1991;Herrel et al 2002;Leal et al 2002;Losos et al 1998). However, some phylogenetic comparative analyses reveal that associations between ecology and morphology are often complex and difficult to detect.…”

Global diversity of lizards in freshwater (Reptilia: Lacertilia)

“…Higher order relationships of these families to one another are discussed by Townsend et al (2004) and Lee (2005). Information on freshwater lizard systematics, distribution and natural history may be found in the works of Pianka and Vitt (2003) (World), Blanc (1967), Glaw & Vences (1994), Böhme et al (2000) (Afrotropical), Beebe (1945), Howland et al (1990), Avila-Pires (1995), Vitt & Avila-Pires (1998), Leal et al (2002), Doan & Castoe (2005) Sprackland (1972), Mägdefrau (1987), Darevsky et al (2004), Honda et al (2006) Shine (1986), Daniels (1987), and Greer (1989) (Australasian).…”

“…Aquatic lizards vary significantly in size and body form and few generalizations can be made as to morphological features indicative of an aquatic lifestyle; even within the genus Anolis, the seven aquatic forms share few features in common (Leal et al 2002). A laterally compressed tail, however, is common to most aquatic lizards (Bedford & Christian 1996) and rugose or keeled body scalation is exhibited by many (e.g., Lanthanotus, Neusticurus, Tropidophorus, and Cophoscincopus).…”