Parallel evolution of the melanic form of the California legless lizard, Anniella pulchra, inferred from mitochondrial DNA sequence variation

The phylogenetic relationships among populations of the fossorial Californi a legless lizard, Anniella pulchra. were examined by sequencing a 990-bp re gion of the mitochondrial cytochrome b gene. The mitochondrial DNA gene tre e was then compared with the geographic distributions of two currently reco gnized subspecies: A. p. nigra, a melanic form restricted to two disjunct c oastal populations, and A. p, pulchra, a more widely distributed, silvery f orm. We tested the null hypothesis that all A. p. nigra form a clade that i s monophyletic with respect to A. p. pulchra. Our results strongly reject t he monophyletic origin of the melanic forms and suggest that the two popula tions of the nominal subspecies A. p. nigra may have arisen independently f rom different ancestral populations in a parallel evolutionary response to selection in cool, coastal habitats.