Ephemeral Pleistocene woodlands connect the dots for highland rattlesnakes of the Crotalus intermedius group

Abstract

Aim To test how Pleistocene climatic changes affected diversification of the Crotalus intermedius species complex. Location Highlands of Mexico and the south‐western United States (Arizona). Methods We synthesize the matrilineal genealogy based on 2406 base pairs of mitochondrial DNA sequences, fossil‐calibrated molecular dating, reconstruction of ancestral geographic ranges, and climate‐based modelling of species distributions to evaluate the history of female dispersion. Results The presently fragmented distribution of the C. intermedius group is the result of both Neogene vicariance and Pleistocene pine–oak habitat fragmentation. Most lineages appear to have a Quaternary origin. The Sierra Madre del Sur and northern Sierra Madre Oriental are likely to have been colonized during this time. Species distribution models for the Last Glacial Maximum predict expansions of suitable habitat for taxa in the southern Sierra Madre Occidental and northern Sierra Madre Oriental. Main conclusions Lineage diversification in the C. intermedius group is a consequence of Pleistocene climate cycling. Distribution models for two sister taxa in the northern and southern Sierra Madre Occidental and northern Sierra Madre Oriental during the Last Glacial Maximum provide evidence for the expansion of pine–oak habitat across the Central Mexican Plateau. Downward displacement and subsequent expansions of highland vegetation across Mexico during cooler glacial cycles may have allowed dispersal between highlands, which resulted in contact between previously isolated taxa and the colonization of new habitats.

Análise preliminar revela baixos níveis de diversidade na estrutura filogeográfica da cascavel mexicana Crotalus polystictus (Serpentes: Viperidae).

“…Bryson et al (2011a) concluded that major lineages in the C. triseriatus Group diverged through orogenic vicariance during the late Neogene, with most phylogeographic structuring within these major lineages attri butable to Quaternary glacialinterglacial climatic cycles. A similar pattern was recovered for the C. intermedius Group, although lineage formation was biased toward the Quaternary rather than the Neogene (Bryson et al 2011b). Because C. polystictus occurs at high elevations, but does not inhabit montane forests, it may have responded differently to Quaternary climatic events than have progenitors of the C. triseriatus and C. intermedius groups, the members of which primarily inhabit pine-oak forests.…”

Phylogeny-Based Comparative Analysis of Venom Proteome Variation in a Clade of Rattlesnakes (Sistrurus sp.)

“…We used the species tree topology and associated multilocus-based branch lengths from Kubatko et al [22] as our estimate of the phylogeny for this group with the exception that we added C. atrox to the phylogeny. To estimate a value for the multilocus branch length connecting C. atrox with the Sistrurus ingroup clade, we used divergence estimates based on mtDNA ATP6–8 gene sequences from C. atrox [30] and S. miliarius and S. catenatus [22]. Venom composition for each taxa was measured as the relative percent of total venom composition made up by proteins from distinct families using data from this study and Sanz et al [23] for Sistrurus , Calvete et al [25] for C. atrox and Calvete et al [unpublished data – see Supplemental Information] for A. c. contortrix .…”

“…[22]. Branch lengths for C. atro x were estimated based on mtDNA ATP6–8 gene sequence divergences between C. atrox [30] and S. miliarius and S. catenatus [22].…”

New species in the Sitalcina sura species group (Opiliones, Laniatores, Phalangodidae), with evidence for a biogeographic link between California desert canyons and Arizona sky islands

“…In Arizona and northern mainland Mexico (Sonora), unsampled populations are predicted to occur in montane habitats between known Sitalcina catalina - Sitalcina rothi populations, and south of our current sample. We are not aware of Sitalcina records from northern mainland Mexico, but based on habitat and distribution of other regional sky-island animal taxa (e.g., Maddison and McMahon 2000, Bryson et al 2011, Bryson et al 2013, Grummer et al 2014), we expect Sitalcina to occur in the mountains of Sonora.…”

“…For many lineages, montane populations in southern Arizona constitute a “northern tip of a southern iceberg”, with centers of distribution found in northern Mexico (e.g., montane jumping spiders - Maddison and McMahon 2000, montane rattlesnakes - Bryson et al 2011). The desert canyons of southern California plus Baja California Norte constitute another distributional area with potentially high unknown diversity.…”