COLOR PATTERNS AND ZONES OF INTERGRADATION IN THE ALAMEDA WHIPSNAKE (MASTICOPHIS LATERALIS EURYXANTHUS) AND CHAPARRAL WHIPSNAKE (M. L. LATERALIS).
Karen E. Swaim; Swaim Biological Inc.; 4435 First Street, PMB 312, Livermore, CA, 94551; (925) 455-8770; kswaim@swaimbio.com; E.J. Britt, M. Yacelga, R. Stoelting, J.Q. Richmond, C. Swaim, Eric J. Britt
The Alameda whipsnake (Masticophis lateralis euryxanthus Riemer 1954) is one of two subspecies of the California whipsnake (Masticophis lateralis [Hallowell 1853]). The subspecies are purportedly distinguished based on differences in phenotype in the form of color characters. However, the geographic boundaries and phenotypic distinctiveness of the two forms have never been examined in a formal quantitative analysis. From an evaluation of nine color characters, when we assessed each character individually in a geographic context, nonparametric tests identified population-level and ontogenetic variation in many of the supposed diagnostic character states, and notable intergradation among states near the putative southern range boundary of M. l. euryxanthus. However, results of multivariate statistical analyses showed that the two subspecies were statistically different when all characters were considered collectively. The zone of morphological intergradation occurs within the same geographic area where M. lateralis populations show genetic admixture between regionally divergent clusters, suggesting that the two morphs display at least some evolutionary distinctiveness. These findings provide the first quantitative evidence that protection for the Alameda whipsnake under the CESA/ESA is warranted, although further work is needed to more precisely delimit the geography of the transition zone in terms of the nuclear genome and morphology.
The Anthropocene: Speciation & Hybridization