Meeting Abstract
63.5 Tuesday, Jan. 6 Convergence and parallelism in the evolution of Anolis tail length MAHLER, D.L.; Harvard University lmahler@oeb.harvard.edu
In Anolis lizards, similar environments have spurred the evolution of similar species numerous times. But have these species evolved to look the same via the same mechanisms (parallelism), or has similarity been achieved through different evolutionary pathways (convergence)? Using data on a broad diversity of neotropical anoles, I asked several questions about the relative roles of convergent and parallel processes in the evolution of long and short tails. Typically, in Anolis, grass dwelling lizards have relatively long tails whereas twig and branch specialists have short, but semi-prehensile tails. These repeated patterns are thought to reflect common locomotor solutions to similar ecological conditions. However, anole tail length may change as a result of two different developmental processes, namely serial addition (or subtraction) of vertebrae versus elongation (or shortening) of individual vertebrae (henceforth referred to as addition versus elongation). I generated radiographs from more than one hundred Caribbean and mainland anole species to determine whether relatively long and short-tailed species achieved their tail lengths via addition or elongation. I examined these traits in the context of the anole phylogeny to ask: 1.) Is tail length convergence achieved through developmental convergence or parallelism? 2.) Which mechanism of length change (elongation or addition) exhibits greater evolutionary lability? 3.) Are the strategies of addition versus elongation associated with particular clades? 4.) Do addition and elongation correspond with particular ecological or morphological specializations? This study has important implications for understanding the processes underlying the repeated evolution of ecomorphological similarity in anoles, and provides one assay of whether superficially convergent species have arrived at similar endpoints through similar or unique developmental means.
