Mitochondrial DNA-based phylogeography of North American rubber boas, Charina bottae (Serpentes : Boidae)

We used 783 bp of mitochondrial DNA sequences to study the phylogeography o f Charina bottae (rubber boa) in western North America, with an emphasis on populations from California (U.S.A.). Maximum-parsimony and maximum-likeli hood methods identified a basal divergence within C. bottae that correspond s to southern and northern segments of its current distribution. These clad es coincide with the ranges of the two recognized subspecies, C. b. umbrati ca in the south and C. b. bottae to the north. A subsequent cladogenetic ev ent in the C. b. bottae clade resulted in two groupings, which we refer to as the Sierra Nevada and the Northwestern subclades, based on the geographi c distribution of their constituent populations. The two subclades have com pletely allopatric distributions, with a genetic break in the vicinity of L assen Volcanic National Park in northeastern California, an area that was s ubjected to glaciation during the Pleistocene and that has been volcanicall y active in the past 100 years. An earlier genetic study documented fixed d ifferences between populations of bottae and umbratica in four of seven all ozymes surveyed, and despite noticeable variation and overlap in the charac ters that define C. b. bottae and C. b. umbratica, the two forms still can be separated in most cases using a suite of morphological. traits. All avai lable evidence thus indicates that C. b. umbratica is a genetically cohesiv e, allopatric taxon that is morphologically diagnosable, and we conclude th at it is an independent evolutionary unit that should be recognized as a di stinct species, Charina umbratica. (C) 2001 Academic Press.