Statistical testing of rapid radiations of the Eulaemus clade of the most diverse South American lizard genus Liolaemus (Liolaemini, Squamata).

OLAVE, M.; AVILA, L. J.; SITES, J.W., JR.; MORANDO, M.

Ottawa

Congreso; First Joint Congress on Evolutionary Biology; 2012

Lack of resolution in a phylogenetic tree is usually represented as a polytomy, and often adding more data (loci and taxa) resolves the species tree. These are the ?soft? polytomies, but in other cases additional data fail to resolve relationships (?hard? polytomies). This last case is often interpreted as simultaneous radiations of lineages in the history of a clade. While hard polytomies are difficult to address, model-based approaches provide tools to test these hypotheses. Here we used a clade of 144 species of the South American lizard clade Eulaemus to estimate phylogenies using a traditional concatenated matrix and three species tree methods: *BEAST, BEST and MDC. The different species tree methods recover largely discordant results, but all resolve the same hard polytomy, (e.g. very short internodes among lineages and low nodal support in Bayesian methods). We simulated datasets under eight explicit evolutionary models (including hard polytomies), tested these against empirical data, and found support for two hard polytomies as the most plausible hypothesis for diversification of this clade. We discuss the performance of these methods and their limitations under the challenging scenario of hard polytomies.