Parallel Evolution of the Melanic Form of the California Legless Lizard, Anniella Pulchra, Inferred From Mitochondrial Dna Sequence Variation

Abstract

The phylogenetic relationships among populations of the fossorial California legless lizard, Anniella pulchra, were examined by sequencing a 990-bp region of the mitochondrial cytochrome b gene. The mitochondrial DNA gene tree was then compared with the geographic distributions of two currently recognized subspecies: A. p. nigra, a melanic form restricted to two disjunct coastal populations, and A. p. pulchra, a more widely distributed, silvery form. We tested the null hypothesis that all A. p. nigra form a clade that is monophyletic with respect to A. p. pulchra. Our results strongly reject the monophyletic origin of the melanic forms and suggest that the two populations of the nominal subspecies A. p. nigra may have arisen independently from different ancestral populations in a parallel evolutionary response to selection in cool, coastal habitats.

Unraveling the thread of nature’s tapestry: the genetics of diversity and convergence in animal pigmentation

“…Other reptiles have locally differentiated signaling colors, possibly due to sexual selection (e.g., variation in male ornaments like Anolis dewlaps; Nicholson et al, 2007). Finally, some reptiles exhibit geographic variation in coloration that cannot be unambiguously linked to particular environmental pressures (e.g., legless lizards on islands ⁄ coasts are darker than their inland counterparts; Pearse and Pogson, 2000).…”

“…Third, it is important to ask whether convergent phenotypes have a similar molecular basis in a broader sample of reptiles. Melanism is an excellent focal phenotype because many reptile species have convergently evolved melanic dorsal coloration (e.g., associated with dark lava substrates and coastal or island regions; King, 1988;Pearse and Pogson, 2000;Rosenblum et al, 2004). However, melanin-based traits are only one aspect of reptile coloration.…”

Rapid parallel evolution of standing variation in a single, complex, genomic region is associated with life history in steelhead/rainbow trout

“…In addition, when the same traits respond to similar selective pressures in multiple species or populations, parallel evolution may lead to similar phenotypic changes [9][10][11]. In such cases, these parallel phenotypic changes may have the same underlying genetic basis [12 -17] or may involve different genetic changes that cause similar phenotypic responses [18,19].…”

Parallel evolution of the summer steelhead ecotype in multiple populations from Oregon and Northern California

“…Similarities in the selective pressures experienced by populations or species can lead to convergent phenotypes (Pearse and Pogson 2000;Steiner et al 2009;Rosenblum et al 2010), although the underlying genetic change associated with the phenotypic trait may be the same (Cresko et al 2004;Mundy et al 2004;Colosimo et al 2005;Gross et al 2009;Miller et al 2012;Hohenlohe et al 2012;Protejo-Garcia et al 2013;Pearse et al 2014), or different (Jessen et al 1991Chen et al 1997;Hoekstra and Nachman 2003). Thus, a first step in understanding the evolution of phenotypic variation in life-history traits is to compare the genetic relationships among populations with the same, and different, phenotypes.…”