A phylogeny of the high-elevation Tibetan megophryid frogs and evidence for the multiple origins of reversed sexual size dimorphism


Jinzhong Fu, Department of Integrative Biology, University of Guelph, Guelph, ON N1G 2W1, Canada. Tel: 519 824 4120 ext. 52715; Fax: 519 767 1656
Email: jfu@uoguelph.ca


A molecular phylogeny of the high-elevation Tibetan megophryid frogs was reconstructed using mitochondrial and nuclear gene sequences. Both parsimony and Bayesian analysis produced similar tree topologies, which identified the genus Leptobrachium as a sister group to Vibrissaphora, and the genera Oreolalax and Scutiger as monophyletic groups. Within the latter two genera, several species groups were also clearly recognized. At least 13 megophryids display reversed sexual size dimorphism (RSSD), where males are equal to or larger than females. According to our phylogenetic hypothesis, RSSD may have independently evolved at least five times or as many as seven times in this group. The multiple origins of RSSD within this group provide an excellent opportunity for studying the relationship between body size sexual dimorphism and other life-history traits and for determining the costs and benefits of RSSD.