Lizards of the Plestiodon skiltonianus species complex are widespread across California and come in two morphotypes the large bodied P. gilberti which is found in arid habitats, and the small bodied mesic dwelling P. skiltonianus. The large bodied morphospecies and the small bodied species are reproductively isolated by a mechanical incompatability, but the large bodied populations are able to reproduce when they come into contact as are the small bodied populations (Richmond and Jockusch 2007). The association of the large bodied populations with arid habitats suggests divergent adaptive pressures have led to the repeated evolution of the large bodied P. gilberti, however to date, niche evolution and niche divergence have not been investigated in this system. Using a combination of mechanistic physiology-based models and species distribution models Jon Richmond and I have analysed niche divergence among the two morphotypes to assess if the two forms have divergent niches related to divergent environments. We find evidence that niche divergence has occurred between the two morphospecies, which is consistent with the requirements of ecological speciation mediated by thermal gradients.
We are now continuing this work by looking at very fine-scale landscape ecology to determine if there are landscape variables that impact habitat usage by these morphospecies in areas where they occur in close proximity.
G. O. U. Wogan and J. Q. Richmond. 2015. Niche divergence builds the case for ecological speciation in skinks of the Plestiodon skiltonianus species complex. Ecology and Evolution. DOI: 10.1002/ece3.1610