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ABSTRACT: Using a multilocus approach, we investigated the tempo and pattern of diversification in a widely distributed New World songbird, the cardinalid genus Pheucticus. Each of the three geographic groups recovered (North American, Middle American, and South American) was comprised of a pair of currently recognized species, and four, three, and three geographically and genetically distinct phylogeographic lineages respectively. Diversification within Pheucticus appears to have occurred at a relatively constant pace throughout the Pleistocene and evenly across a broad latitudinal distribution. The Isthmus of Panama completion and Pleistocene glacial cycles both appear to have played prominent roles in the diversification of this group.
Molecular Phylogenetics and Evolution 06/2013; · 3.61 Impact Factor
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ABSTRACT: Interpretations of phylogeographic patterns can change when analyses shift from single gene-tree to multilocus coalescent analyses. Using multilocus coalescent approaches, a species tree and divergence times can be estimated from a set of gene trees while accounting for gene-tree stochasticity. We utilized the conceptual strengths of a multilocus coalescent approach coupled with complete range-wide sampling to examine the speciation history of a broadly distributed, North American warm-desert toad, Anaxyrus punctatus. Phylogenetic analyses provided strong support for three major lineages within A. punctatus. Each lineage broadly corresponded to one of three desert regions. Early speciation in A. punctatus appeared linked to late Miocene-Pliocene development of the Baja California peninsula. This event was likely followed by a Pleistocene divergence associated with the separation of the Chihuahuan and Sonoran Deserts. Our multilocus coalescent-based reconstruction provides an informative contrast to previous single gene-tree estimates of the evolutionary history of A. punctatus.
Molecular Phylogenetics and Evolution 05/2012; 64(3):393-400. · 3.61 Impact Factor
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ABSTRACT: Neogene vicariance during the Miocene and Pliocene and Quaternary climate change have synergistically driven diversification in Mexican highland taxa. We investigated the impacts of these processes on genetic diversification in the widely distributed bunchgrass lizards in the Sceloporus scalaris group. We searched for correlations between timing in diversification and timing of (1) a period of marked volcanism across the Trans-Mexican Volcanic Belt in central Mexico 3-7.5million years ago (Ma) and (2) a transition to larger glacial-interglacial cycles during the mid-Pleistocene. From our phylogenetic analyses of mitochondrial DNA we identified two major clades that contained 13 strongly supported lineages. One clade contained lineages from the two northern sierras of Mexico, and the other clade included lineages associated with the Trans-Mexican Volcanic Belt and Central Mexican Plateau. Results provided support for Neogene divergences within the S. scalaris group in response to uplift of the Trans-Mexican Volcanic Belt, a pattern observed in several co-distributed taxa, and suggested that Quaternary climate change likely had little effect on diversification between lineages. Uplift of the Trans-Mexican Volcanic Belt during specific time periods appears to have strongly impacted diversification in Mexican highland taxa.
Molecular Phylogenetics and Evolution 10/2011; 62(1):447-57. · 3.61 Impact Factor
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ABSTRACT: The widespread montane Mexican horned lizard Phrynosoma orbiculare (Squamata: Phrynosomatidae) represents an ideal species to investigate the relative impacts of Neogene vicariance and Quaternary climate change on lineage diversification across the Mexican highlands. We used mitochondrial DNA to examine the maternal history of P. orbiculare and estimate the timing and tempo of lineage diversification. Based on our results, we inferred 11 geographically structured, well supported mitochondrial lineages within this species, suggesting P. orbiculare represents a species complex. Six divergences between lineages likely occurred during the Late Miocene and Pliocene, and four splits probably happened during the Pleistocene. Diversification rate appeared relatively constant through time. Spatial and temporal divergences between lineages of P. orbiculare and co-distributed taxa suggest that a distinct period of uplifting of the Transvolcanic Belt around 7.5-3 million years ago broadly impacted diversification in taxa associated with this mountain range. To the north, several river drainages acting as filter barriers differentially subdivided co-distributed highland taxa through time. Diversification patterns observed in P. orbiculare provide additional insight into the mechanisms that impacted differentiation of highland taxa across the complex Mexican highlands.
Molecular Phylogenetics and Evolution 09/2011; 62(1):87-96. · 3.61 Impact Factor
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ABSTRACT: Studies of speciation and taxon delimitation are usually decoupled. Combining these methods provides a stronger theoretical ground for recognizing new taxa and understanding processes of speciation. Using coalescent methods, we examine speciation, post-speciation population demographics, and taxon delimitation in the Arizona Mountain Kingsnake (Lampropeltis pyromelana), a species restricted to high elevations in southwestern United States and northern Mexico (SW). These methods provide a solid foundation for understanding how biogeographic barriers operate at the regional scale in the SW. Bayesian species delimitation methods, using three loci from samples of L. pyromelana taken throughout their range, show strong support for the existence of two species that are separated by low elevation habitats found between the Colorado Plateau/ Mogollon Rim and the Sierra Madre Occidental. Our results suggest an allopatric mode of speciation given the near absence of gene flow over time, which resulted in two lineages of unequal population sizes. Speciation likely occurred prior to the Pleistocene, during the aridification of the SW and/or the uplift of the Colorado Plateau, and while these species occupy similar high-elevation niches, they are isolated by xeric conditions found in the intervening low deserts. Furthermore, post-speciation demographics suggest that populations of both lineages were not negatively impacted by climate change throughout the Pleistocene. Finally, our results suggest that at least for this group, where divergence is old and gene flow is low, Bayesian species delimitation performs well.
Molecular Phylogenetics and Evolution 05/2011; 60(3):445-54. · 3.61 Impact Factor
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ABSTRACT: We investigate the evolutionary history of the wide-ranging Nearctic treefrog Hyla arenicolor through the integration of extensive range-wide sampling, phylogenetic analyses of multilocus genetic data, and divergence dating. Previous phylogeographic studies of this frog documented a potential signature of introgressive hybridization from an ecologically and morphologically divergent sister species. Based on our Bayesian phylogenetic analyses of mitochondrial DNA, we inferred strong phylogeographic structure in H. arenicolor as indicated by seven well-supported clades, five of which correspond to well-defined biogeographic regions. Clades from the Balsas Basin and southwestern Central Mexican Plateau in Mexico, and the Grand Canyon of Arizona, group with the morphologically, behaviorally, and ecologically divergent mountain treefrogs in the H. eximia group, rendering H. arenicolor as paraphyletic. The phylogenetic position of at least two of these three H. arenicolor clades within the H. eximia group, however, is most likely the result of several episodes of introgressive hybridization and subsequent mitochondrial gene capture separated in time and space, as supported by evidence from the nuclear genes. Hyla arenicolor from the Balsas Basin appear to be deeply divergent from other H. arenicolor and represent a distinctly different species. Results suggests that introgressive hybridization events, both ancient and contemporary, coupled with late Neogene vicariance and Pleistocene climate-driven range shifts, have all played a role in the historical diversification of H. arenicolor.
Evolution 08/2010; 64(8):2315-30. · 5.15 Impact Factor
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ABSTRACT: The systematic relationships of snakes in the Lampropeltis mexicana complex (L. mexicana, L. alterna, and L. ruthveni) are poorly known despite several taxonomic studies over the last 80 years. Mitochondrial DNA sequences were used to infer the phylogeny of the L. mexicana complex. At least one representative sample from the nine currently recognized species of Lampropeltis was sequenced. Our results suggest that a deep basal split resulted in the divergence of two groups of Lampropeltis, with one group occupying the upland areas of western United States and most of western and central Mexico, and the other northeastern Mexico and the lowland areas of the southern United States. Results also revealed that the L. mexicana complex and Lampropeltis triangulum are polyphyletic, with taxa from both groups nested together in deeply divergent northern and southern clades. These results are incongruent with previous hypotheses of phylogenetic relationships based on morphology, and suggest that morphological characters shared among the various tri-colored Lampropeltis (e.g., hemipenal structure and tri-colored pattern) may be difficult to interpret phylogenetically.
Molecular Phylogenetics and Evolution 06/2007; 43(2):674-84. · 3.61 Impact Factor
