|Pristimantis urichi, a Terrarana Frog. JCM|
Some evolutionary lineages have been much more successful at producing more individual species than others. Lizards of the genus Anolis and snakes in the genus Atractus have been particularly sucessful at producing large numbers of species. Gonzalez-Voyer and colleagues have used a comparative anayslis to examine correlates of species richness for the largest radiation of Neotropical frogs, the direct-developing frogs, the Terrarana. More than 900 species are known to compose the Terrarana clade, and they make up almost 33% ofl New World Tropical frogs and 16% of the world's described species. The authord found that time the clade had been around - its age- was not significant in explain the Terrarana clade's variation in species richness. Instead, they found ecological and morphological traits explained 65% of the variance in species richness. The traits included a more vascularized ventral skin, the ability to colonize high-altitudes, and use a variety of vegetation types. These traits had a significant correlation with species richness, while large body size was marginally correlated with species richness.Thus. high-altitudes play a role in shaping clade diversity in the Neotropics while intrinsic factors, such as skin structures and possibly body size, may ultimately determine which clades are more speciose than others.
GONZALEZ-VOYER, A., PADIAL, J. M., CASTROVIEJO-FISHER, S., DE LA RIVA, I. and VILÀ, C. (2011), Correlates of species richness in the largest Neotropical amphibian radiation. Journal of Evolutionary Biology, 24: 931–942. doi: 10.1111/j.1420-9101.2011.02243.x