Morphological Evolution in the Liolaemus darwinii Species Group (Squamata: Liolaemini) Suggests Adaptive Diversification Associated with Climatic Niches

CAMARGO, A.; MORANDO, M.; AVILA, L.J.; SITES, J.W., JR.

Albuquerque

Congreso; Joint Meeting Ichthyology and Herpetology 2013; 2013

SSAR/HL/ASIH

Patterns of diversification at the macroevolutionary level can be due to adaptative processes or simple random divergence, and adaptive divergence can be driven by natural selection in response to ecological factors and/or sexual selection. We evaluated diversification models in the L. darwinii group using comparative phylogenetic methods. We took seven morphometric measurements for all species, obtained climatic data from georeferenced localities, and used the phylogeny of Camargo et al. (2012). We compared Brownian motion vs. adaptive models of diversification based on the morphological variation mapped on to the phylogeny (R packages picante and geiger). We compared the evolutionary rates among ecomorphological traits and sexual dimorphism based on Mahalanobis and phylogenetic distances among species pairs. We evaluated the evolutionary correlation between the morphological variation and the climatic niches using a phylogenetic canonical correlation analysis (R phytools). Three morphometric traits showed phylogenetic signal and fit a model of adaptive optima better than a Brownian model. Morphological divergence and sexual dimorphism variation was similar between species pairs, suggesting that both natural and sexual selection have operated during diversification of this clade. Taking into account phylogeny, the among- species morphological variation of males is significantly correlated with the variation in climatic niches. These results suggest that adaptive diversification in the L. darwinii group took place as a response to divergent climatic niches in gradients of the Monte Desert in west-central Argentina. Our results also support recent theoretical and empirical findings suggesting that sexual selection can interact with natural selection to complete processes of adaptive speciation.