We thank J. Cabot and J. González for allowing us to study specimens in collections under their care. Manuel Moreno helped in field sampling. J. Hódar and L. Luiselli contributed with valuable comments on the first draft of the manuscript. K. Setser improved the language style. We thank three anonymous reviewers for their very constructive and detailed suggestions and corrections.The last stage of this study was supported by the Research Award REN2000-1376 GLO of the Spanish MCYT to the senior author and to MF.