**Acknowledgements**

Funding was provided by a graduate scholarship grant from CONACYT and a postdoctoral research grant from DGAPA at Universidad Nacional Autónoma de México (UNAM). My ideas about biogeography and diversification were greatly benefited from discussions with Enrique Martinez Meyer, Oscar Flores Villela, Luna Sanchez Reyes and Mark. E. Olson. Thanks to Mark E. Olson to read several draft versions of this manuscript and for his continuous thoughtful comments. All remaining errors are my own.
