Molecular phylogenetic analysis of slender salamanders genus Batrachoseps (Amphibia: Plethodontidae), from central coastal California with descriptions of four new species

Abstract

Plethodontid salamanders of the genus Batrachoseps comprise a clade of morphologically similar, elongate species whose great genetic diversity is being revealed through molecular studies. We used allozymes and mtDNA sequences to study variation in 62 populations from central coastal California, treated most recently as members of the B. pacificus complex. Analyses of mtDNA data identify four lineages that are well differentiated from each other and do not form a monophyletic group. Instead, the central coastal lineages are multiply paraphyletic with respect to the southern California members of the pacificus group. Marked allozymic differences show that these four lineages are strongly differentiated, although some limited gene exchange may have occurred in the past. Each lineage is also morphologically distinctive, but the differences between them are subtle. Because these lineages appear to be evolving independently, we describe them as new species: B. luciae, B. incognitus and B. minor, distributed parapatrically from north to south in the Santa Lucia Mountains of coastal Monterey and San Luis Obispo Counties, and B. gavilanensis, occurring mainly inland from the range of B. luciae, centered on the Gabilan Mountains, but also extending to the Pacific coast at the north end of the range of the complex, along the northern border of Monterey Bay. Although no sympatry is known among any of the new species, B. luciae and B. gavilanensis are narrowly parapatric. Furthermore, all but B. luciae occur in sympatry with other members of the genus in at least a part of their geographic ranges. The new species may have arisen vicariantly with respect both to each other and to related forms in southern California, in part as a result of the dramatic tectonic movements that have characterized the last 15 million years of geological history in western North America.