Falling apart and merging: diversification of slender salamanders (Plethodontidae: Batrachoseps) in the American West

Abstract

The plethodontid genus Batrachoseps, the slender salamanders, is the most diverse clade of salamanders in western North America, but it has posed taxonomic difficulties because it contains many morphologically cryptic species. A segment of the mitochondrial DNA gene cytochrome b was studied for 278 individuals densely sampled from throughout the range of all 18 described species and several undescribed species. Phylogenetic analyses of the mtDNA data identify six major clades, one corresponding to the subgenus Plethopsis and five within a monophyletic subgenus Batrachoseps. All major clades and most species within these clades display strong phylogeographic structuring. Comparisons of mtDNA and allozyme data show that several allozymically cohesive groups are not monophyletic with respect to mtDNA. We suggest that this phenomenon results from fragmentation of populations, divergence in allopatry, and then recontact and gradual merging of units caused predominantly by male‐mediated gene flow. The mtDNA offers evidence that populations were once more isolated than they are now, while the patterns of allozyme variation reflect recent and current interactions among populations. The complex patterns of morphological, allozymic and mtDNA variation associated with the constantly changing geological landscape give insight into the nature of processes responsible for species formation in Batrachoseps. © 2002 The Linnean Society of London. Biological Journal of the Linnean Society, 2002, 76, 361–391.

Patterns of differential introgression in a salamander hybrid zone: inferences from genetic data and ecological niche modelling

“…Jockusch & Wake 2002;García-París et al 2003). However, the available evidence does not support the idea that greater dispersal of male Plethodon underlies the discordant patterns of genetic and morphological variation in the hybrid zone.…”

Genome size, cell size, and the evolution of enucleated erythrocytes in attenuate salamanders

“…Individuals from different mitochondrially-diagnosed population-level lineages (called species for simplicity, although not all meet criteria for species status) were selected to represent each of the major clades of Batrachoseps (Jockusch and Wake, 2002) for measurements of genome size, cell size, RBC enucleation, and phylogenetic analyses. Attempts were made to use the same exemplar taxa for all analyses, but this was not always possible.…”

“…The genus Batrachoseps is a clade of plethodontids comprising 20 named species with distributions in the western United States and Baja California, Mexico. Despite high levels of genetic diversity (Yanev, 1980;Jockusch and Wake, 2002), most species of Batrachoseps exhibit extreme overall morphological stasis. Body form within the genus evolved from a fairly robust ancestral morphology to an attenuated body form with miniaturized limbs and a slender trunk, head, and tail.…”

“…However, one member of the attenuate clade, Batrachoseps stebbinsi, has secondarily evolved a more robust body form. Previous analyses based on the mitochondrial cytochrome-b gene have demonstrated five wellsupported, monophyletic species groups within the attenuate clade (the nigriventris group, the pacificus group, the attenuatus group, the gabrieli group, and the relictus group), but the relationships among them have remained unresolved (Jockusch and Wake, 2002). …”

Supplemental Material for 'The amphibian tree of life. (Bulletin of the AMNH ; no. 297)'

“…Wake et al, 2005), although this may be an artifact of the relatively small size of the group (173 species currently recognized) and the few, mostly coordinated, workers. Salamanders are the best-known group at the species level, but salamander phylogenetic work has largely focused on the generic and infrageneric levels of investigation (e.g., Zhao, 1994;Titus and Larson, 1996;Highton, 1997Highton, , 1998Highton, , 1999García-París and Wake, 2000;Highton and Peabody, 2000;Jockusch et al, 2001;Parra-Olea and Wake, 2001;Jockusch and Wake, 2002;Parra-Olea et al, 2002;Steinfartz et al, 2002;Parra-Olea et al, 2004;Sites et al, 2004), although there have been several important efforts at an overall synthesis of morphological and molecular evidence (Larson and Dimmick, 1993;Larson et al, 2003;Wiens et al, 2005).…”