RESUMEN
Sceloporus subniger Poglaygen Smith is a montane bunchgrass lizard distributed across pine-oak forests of central Mexico. Prompted by the discovery of a new population of this lizard in far western Mexico, and by recent studies suggesting S. subniger may be a composite of several distinct species, we examined in more detail the genetic structure of S. subniger. We generated a mitochondrial DNA (mtDNA) dataset from 81 specimens and an ultraconserved elements (UCE) dataset representing thousands of genomic regions from 12 specimens to specifically evaluate the genetic distinctiveness of populations from western Michoacán and adjacent Jalisco along with the newly discovered population in the Sierra de Mascota in western Jalisco. We also recorded morphological data from 47 museum specimens to compare to our genetic data. Results from our analyses of the genetic data, augmented by specimen measurements and scale counts, support the notion that S. subniger is indeed a composite of distinct species. Montane bunchgrass lizards from western Michoacán and adjacent Jalisco, and from the Sierra de Mascota in western Jalisco, each represent distinct new species, which we describe and name here.
Asunto(s)
Biodiversidad , Lagartos , Animales , Secuencia Conservada/genética , ADN Mitocondrial/genética , Bosques , Lagartos/clasificación , Lagartos/genética , MéxicoRESUMEN
BACKGROUND: A considerable amount of evidence has favored ecological host-fitting, rather than coevolution, as the main mechanism responsible for trypanosome divergence. Nevertheless, beyond the study of human pathogenic trypanosomes, the genetic basis of host specificity among trypanosomes isolated from forest-inhabiting hosts remains largely unknown. METHODS: To test possible scenarios on ecological host-fitting and coevolution, we combined a host capture recapture strategy with parasite genetic data and studied the genetic variation, population dynamics and phylogenetic relationships of Trypanosoma terrestris, a recently described trypanosome species isolated from lowland tapirs in the Brazilian Pantanal and Atlantic Forest biomes. RESULTS: We made inferences of T. terrestris population structure at three possible sources of genetic variation: geography, tapir hosts and 'putative' vectors. We found evidence of a bottleneck affecting the contemporary patterns of parasite genetic structure, resulting in little genetic diversity and no evidence of genetic structure among hosts or biomes. Despite this, a strongly divergent haplotype was recorded at a microgeographical scale in the landscape of Nhecolândia in the Pantanal. However, although tapirs are promoting the dispersion of the parasites through the landscape, neither geographical barriers nor tapir hosts were involved in the isolation of this haplotype. Taken together, these findings suggest that either host-switching promoted by putative vectors or declining tapir population densities are influencing the current parasite population dynamics and genetic structure. Similarly, phylogenetic analyses revealed that T. terrestris is strongly linked to the evolutionary history of its perissodactyl hosts, suggesting a coevolving scenario between Perissodactyla and their trypanosomes. Additionally, T. terrestris and T. grayi are closely related, further indicating that host-switching is a common feature promoting trypanosome evolution. CONCLUSIONS: This study provides two lines of evidence, both micro- and macroevolutionary, suggesting that both host-switching by ecological fitting and coevolution are two important and non-mutually-exclusive processes driving the evolution of trypanosomes. In line with other parasite systems, our results support that even in the face of host specialization and coevolution, host-switching may be common and is an important determinant of parasite diversification.
Asunto(s)
Perisodáctilos/parasitología , Trypanosoma/clasificación , Caimanes y Cocodrilos/parasitología , Animales , Teorema de Bayes , Coevolución Biológica , Análisis por Conglomerados , Fenómenos Ecológicos y Ambientales , Ecosistema , Variación Genética , Genética de Población , Interacciones Huésped-Parásitos , Filogenia , Dinámica Poblacional , Trypanosoma/genética , Trypanosoma/crecimiento & desarrolloRESUMEN
Mountain formation in Mexico has played an important role in the diversification of many Mexican taxa. The Trans-Mexican Volcanic Belt in particular has served as both a cradle of diversification and conduit for dispersal. We investigated the evolutionary history of the Isthmura bellii group of salamanders, a widespread amphibian across the Mexican highlands, using sequence capture of ultraconserved elements. Results suggest that the I. bellii group probably originated in southeastern Mexico in the late Miocene and later dispersed across the Trans-Mexican Volcanic Belt and into the Sierra Madre Occidental. Pre-Pleistocene uplift of the Trans-Volcanic Belt likely promoted early diversification by serving as a mesic land-bridge across central Mexico. These findings highlight the importance of the Trans-Volcanic Belt in generating Mexico's rich biodiversity.
Asunto(s)
Ecosistema , Filogenia , Urodelos/clasificación , Urodelos/genética , Animales , Teorema de Bayes , Calibración , México , Filogeografía , Factores de TiempoRESUMEN
Interspecific gene flow is pervasive throughout the tree of life. Although detecting gene flow between populations has been facilitated by new analytical approaches, determining the timing and geography of hybridization has remained difficult, particularly for historical gene flow. A geographically explicit phylogenetic approach is needed to determine the overlap of ancestral populations. In this study, we performed population genetic analyses, species delimitation, simulations and a recently developed approach of species tree diffusion to infer the phylogeographic history, timing and geographic extent of gene flow in lizards of the Sceloporus spinosus group. The two species in this group, S. spinosus and S. horridus, are distributed in eastern and western portions of Mexico, respectively, but populations of these species are sympatric in the southern Mexican highlands. We generated data consisting of three mitochondrial genes and eight nuclear loci for 148 and 68 individuals, respectively. We delimited six lineages in this group, but found strong evidence of mito-nuclear discordance in sympatric populations of S. spinosus and S. horridus owing to mitochondrial introgression. We used coalescent simulations to differentiate ancestral gene flow from secondary contact, but found mixed support for these two models. Bayesian phylogeography indicated more than 60% range overlap between ancestral S. spinosus and S. horridus populations since the time of their divergence. Isolation-migration analyses, however, revealed near-zero levels of gene flow between these ancestral populations. Interpreting results from both simulations and empirical data indicate that despite a long history of sympatry among these two species, gene flow in this group has only recently occurred.
Asunto(s)
Flujo Génico , Genética de Población , Lagartos/genética , Filogenia , Simpatría , Animales , Teorema de Bayes , Núcleo Celular/genética , ADN Mitocondrial/genética , Funciones de Verosimilitud , México , Modelos Genéticos , Modelos Estadísticos , Datos de Secuencia Molecular , Filogeografía , Análisis de Secuencia de ADNRESUMEN
A new species of bunchgrass lizard in the Sceloporus scalaris group is described from the southern portion of the Sierra Madre Occidental in Mexico. The new species, Sceloporus aurantius sp. nov., was previously confused with S. brownorum but differs from this and all but one species within the S. scalaris group by a lack of blue belly patches in males. It shares with S. chaneyi an absence of blue belly patches, but differs from this species in size, number of dorsal scales, number of scales around midbody, and presence of an un-patterned morph. The new species further differs from S. chaneyi, and all other species in the S. scalaris species group, by unique phylogenetic position revealed through species delimitation based on multi-locus nuclear DNA. Principal component analyses of 24 traditional morphological characters used to describe previous S. scalaris group taxa indicate that these characters may be of limited use to delineate species in this species group. However, male lateral and ventral coloration may still be an important character for diagnosing species.