Lack of Convergence in Aquatic Anolis Lizards

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.

Brain Organization and Habitat Complexity in <b><i>Anolis </i></b>Lizards

“…The lack of correlation between neuroanatomy and RHC across the six species of anoles sampled in this study was unexpected, particularly in light of the rich literature showing that habitat preference has a major effect on many aspects of anole biology [review in Losos, 2009; but see Leal et al, 2002]. Why neuroanatomy does not follow the same trend as other morphological and behavioral traits in anoles is an open question.…”

The Effect of Intraspecific Sample Size on Type I and Type Ii Error Rates in Comparative Studies

“…Because the power of a comparative analysis is a function of the number of species (Freckleton et al 2002), many workers are tempted to maximize the number of species, even if it means measuring few (at the extreme, one) individuals of each species (e.g., Leal et al 2002;Patek and Oakley 2003;Ackerly and Nyffeler 2004;Al-kahtani et al 2004). Measuring few individuals per species increases the probability that species' characteristics will be estimated with error, perhaps even substantial error.…”

Parallel Evolution in Ecological and Reproductive Traits to Produce Cryptic Damselfly Species Across the Holarctic

“…Likewise, sticklebacks have diversified into limnetic and benthic forms in multiple lakes (Schluter and Nagel 1995;Albert and Schluter 2004;Boughman et al 2005). Parallel evolution is expected when different lineages experience similar ecological conditions, such as those associated with microhabitat use and diet, since natural selection will often favor similar solutions to the ecological problems faced by lineages in different geographic areas (e.g., Schluter and Nagel 1995;Losos et al 1998;Rü ber et al 1999;Cassens et al 2000; but see Leal et al 2002).…”