Data and data interpretation in the study of limb evolution: A reply to Galis et al. On the reevolution of digits in the lizard genus bachia

Galis and collaborators (2010) claim that our recent paper (Kohlsdorf and Wagner 2006), presenting statistical evidence for the reevolution of digits in the genus Bachia, may be flawed. Their reanalysis of the data does not support the possibility of a reevolution of digits and the authors also argue that such a reevolution would be implausible on functional and developmental grounds. In response, we reanalyzed our data with additional outgroup species. Our results differ from the one published in 2006, but this incongruence is not statistically significant. In contrast, the hypothesis presented by Galis et al. is significantly worse. An analysis of digit number evolution, using novel techniques to test for irreversibility of character loss (Goldberg and Igic 2008), confirmed our original conclusion that there is strong evidence for reevolution of digits in Bachia. We also point out that this result is not in conflict with the hypothesis by Galis and Metz (2001) that mutations affecting the initial digit patterning are associated with strong negative pleiotropic effects and thus unlikely to be fixed in evolution. An important avenue of future research will be to directly test whether reevolved digits develop from conserved digit condensations retained after digit loss.