[show abstract][hide abstract] ABSTRACT: Multivariate analyses of morphological characters provide strong evidence that a highland Vaejovis from the Sierra de los Ajos, a Madrean 'sky island' in northern Sonora, Mexico, represents a distinct new species of the V. vorhiesi group. This new species is described and compared to other geographically adjacent species of the V. vorhiesi group, named V. bandido, and brief notes on ecology are provided. Results from this study provide evidence that multivariate analysis of morphological characters is a powerful tool to delimit small and otherwise cryptic scorpion species.
Journal of Arachnology 01/2012; 40(3):281-290. · 0.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aim We used inferences of phylogeographical structure and estimates of divergence times for three species of gophersnakes (Colubridae: Pituophis) distributed across the Mexican Transition Zone (MTZ) to evaluate the postulated association of three Neogene geological events (marine seaway inundation of the Isthmus of Tehuantepec, formation of the Transvolcanic Belt across central Mexico, and secondary uplifting of the Sierra Madre Occidental) and of Pleistocene climate change with inter- and intraspecific diversification.Location Mexico, Guatemala, and the western United States.Methods We combined range-wide sampling (67 individuals representing three putative species distributed across northern Middle America and western North America) and phylogenetic analyses of 1637 base pairs of mitochondrial DNA to estimate genealogical relationships and divergence times. The hypothesized concordance of inferred gene trees with geological histories was assessed using topology tests.Results We identified three major lineages of Middle American gophersnakes, and strong phylogeographical structure within each lineage. Gene trees were statistically congruent with hypothesized geological histories for two of the three postulated geological events. Estimated divergence dates and the geographical distribution of genetic variation further support mixed responses to these geological events. Considerable phylogeographical structure appears to have been generated during the Pleistocene.Main conclusions Phylogenetic and phylogeographical structure in gophersnakes distributed across northern Middle America and western North America highlights the influence of both Neogene vicariance events and Pleistocene climate change in shaping genetic diversity in this region. Despite the presence of two major geographical barriers in southern Mexico, extreme geological and environmental heterogeneity in this area may have differentially structured genetic diversity in highland taxa. To the north, co-distributed taxa may display a more predictable pattern of diversification across the warm desert regions. Future studies should incorporate nuclear data to disentangle inferred lineage boundaries and further elucidate patterns of mitochondrial introgression.
[show abstract][hide abstract] 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
Journal of Biogeography 01/2011; 38(12):2299-2310. · 4.86 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aim To assess the genealogical relationships of widespread montane rattlesnakes in the Crotalus triseriatus species group and to clarify the role of Late Neogene mountain building and Pleistocene pine–oak forest fragmentation in driving the diversification of Mexican highland taxa.Location Highlands of mainland Mexico and the south-western United States (Texas, New Mexico, and Arizona).Methods A synthesis of inferences was used to address several associated questions about the biogeography of the Mexican highlands and the evolutionary drivers of phylogeographical diversity in co-distributed taxa. We combined extensive range-wide sampling (130 individuals representing five putative species) and mixed-model phylogenetic analyses of 2408 base pairs of mitochondrial DNA to estimate genealogical relationships and divergence times within the C. triseriatus species group. We then assessed the tempo of diversification using a maximum likelihood framework based on the birth–death process. Estimated times of divergences provided a probabilistic temporal component and questioned whether diversification rates have remained constant or varied over time. Finally, we looked for phylogeographical patterns in other co-distributed taxa.Results We identified eight major lineages within the C. triseriatus group, and inferred strong correspondence between maternal and geographic history within most lineages. At least one cryptic species was detected. Relationships among lineages were generally congruent with previous molecular studies, with differences largely attributable to our expanded taxonomic and geographic sampling. Estimated divergences between most major lineages occurred in the Late Miocene and Pliocene. Phylogeographical structure within each lineage appeared to have been generated primarily during the Pleistocene. Although the scale of genetic diversity recognized affected estimated rates of diversification, rates appeared to have been constant through time.Main conclusions The biogeographical history of the C. triseriatus group implies a dynamic history for the highlands of Mexico. The Neogene formation of the Transvolcanic Belt appears responsible for structuring geographic diversity among major lineages. Pleistocene glacial–interglacial climatic cycles and resultant expansions and contractions of the Mexican pine–oak forest appear to have driven widespread divergences within lineages. Climatic change, paired with the complex topography of Mexico, probably produced a myriad of species-specific responses in co-distributed Mexican highland taxa. The high degree of genetic differentiation recovered in our study and others suggests that the Mexican highlands may contain considerably more diversity than currently recognized.
[show abstract][hide abstract] ABSTRACT: Morphological studies have proven inconsistent in establishing the phylogenetic placement and taxonomic assignment of Elgaria parva. Originally classified as Gerrhonotus parvus Knight and Scudday, this taxon was reassigned to Elgaria based on morphology. To investigate its phylogenetic affinities, we generated mitochondrial DNA sequence data and conducted phylogenetic analyses together with published sequences for a broad taxonomic sampling of anguid lizards. We conducted parsimony, likelihood, and Bayesian analyses of the data. Our results indicate that E. parva forms a clade with other Gerrhonotus rather than Elgaria. Furthermore, Elgaria and Gerrhonotus are not sister taxa. Based on our new molecular evidence, we suggest that E. parva be classified as Gerrhonotus parvus as originally described.
Journal of Herpetology 09/2009; · 0.89 Impact Factor