Molecular phylogenetics and evolution of sexual dichromatism among populations of the Yarrow's spiny lizard (Sceloporus jarrovii)

Understanding evolution of geographic variation in sexually dimorphic trait s is critical for understanding the role that sexual selection may play in speciation. We performed a phylogenetic analysis of geographic variation in sexual dichromatism in the Yarrow's spiny lizard (Sceloporus jarrovii), a taxon that exhibits remarkable diversity in male coloration among populatio ns (e.g., black, red, green, yellow, blue, brown). An mtDNA phylogeny based on approximately 880 bp from the 12S ribosomal RNA gene and 890 bp from th e ND4 gene was reconstructed for 30 populations of S. jarrovii and eight ot her species of the torquatus species group using maximum-likelihood and par simony methods. The phylogeny suggests that S. jarrovii consists of at leas t five evolutionary species, none of which are sister taxa. Although intras pecific diversity in male coloration is less than indicated by previous tax onomy, two species formerly referred to as S. jarrovii exhibit impressive g eographic variation in sexual dichromatism. In one of these species, the ph ylogeny shows the independent evolution of a distinctive blue color morph i n different parts of the species range. This pattern suggests that sexual s election may lead to striking phenotypic divergence among conspecific popul ations and striking convergence. Results also demonstrate the importance of a phylogenetic perspective in studies of evolutionary processes within nom inal species and the problematic nature of "polytypic" species recognized u nder the biological species concept.