Disparate Patterns of Diversification Within Liolaemini Lizards

Abstract

Lizards are a major component of temperate-to-tropical terrestrial vertebrate biotas, and have played a central role as model systems for evolutionary and ecological research. The most diverse lizard group of the southern half of South America is the clade Liolaemini (=family Liolaemidae), which includes three genera characterized by large differences in species richness, as well as many other aspects of their biology. At one extreme is the monotypic genus Ctenoblepharys, restricted to sandy beaches and dunes in the coastal desert of Peru, oviparous and insectivorous. At the other extreme, Liolaemus is the world’s richest temperate zone amniote genus of the temperate zone, with 262 described species. Liolaemus is widely distributed across southern South America, from north-central Peru to Tierra del Fuego, inhabiting climatic regimes extending from sea level to 5176 m in Bolivia, and exhibiting great diversity in biological features such as body size, color pattern, diet, reproductive mode (viviparous, oviparous, and one parthenogenetic species) and karyotype. The third clade is the genus Phymaturus, which includes 44 described species distributed along the eastern and western Andean slopes in Argentina and Chile and through Patagonia. All Phymaturus species are viviparous, primarily herbivorous, strictly saxicolous and restricted to volcanic plateaus and peaks. Here, we contrast diversification patterns between the more specialized Phymaturus and Ctenoblepharys, with the more generalist Liolaemus. We found disparate patterns of diversification among the three genera, with Liolaemus showing the highest net diversification rate and, surprisingly, Phymaturus showing the highest speciation rates. The lower species diversity in Phymaturus, however, appears to be due to a high extinction rate, while the extraordinary species richness in Liolaemus is likely due to a lower extinction rate. The monotypic Ctenoblepharys is characterized by a negative net diversification rate, highlighting its vulnerability. We also found evidence of selection acting on the body sizes of Liolaemini species, in the form of a positive correlation between body size evolution and net diversification, speciation and extinction rates in Phymaturus, and a clear slowdown of morphological evolution in the Phymaturus patagonicus clade. We discuss the advantages and disadvantages of generalist vs. specialist life histories in Liolaemini, and provide recommendations for their conservation based on our findings.