The Nuclear Central American Highlands (NCAH) is a mountainous region located within a complex transition zone. Here, we analyzed the distribution patterns of 282 species of resident land birds of the NCAH. We gathered a database with records of presence of species, from which we generated realized ecological niche models using the Genetic Algorithm for Rule Set Production. These ecological niche models were used to obtain maps of each species' potential distribution and generated species richness maps that were also compared to the map of protected areas. In addition, the maps were overlaid with a 0.25 diameter hexagonal grid to generate a presence-absence matrix to create regionalizations through (a) a Parsimony Analysis of Endemism and (b) a phenogram. Results show contrasting patterns of distribution between total species richness and endemic species richness. The regionalizations show groups influenced by slope and altitude. Species composition is mainly Mesoamerican and Neotropical species. Our results offer a new view of the regional understanding of bird diversity patterns and biogeographical processes that have shaped regional richness, like the effects of the Great American Biotic Interchange that are visible in the species composition of the NCAH. We believe that these maps of both species richness and regionalization can serve as useful tools for conservation biologists and authorities in implementing strategies for the protection of natural areas in the NCAH.
Humid tropical forests in Mesoamerica are distributed along the Atlantic slope and, in scattered locations, along the Mexican Pacific slope. These poorly explored Mexican forests include microendemic bird species. Two species in the genus Dendrocolaptes occur in lowland and foothill humid tropical forests of Mesoamerica. One of these, D. sanctithomae, is comprised of four subspecies, of which the two that occur in Mexico, D. s. sanctithomae and D. s. sheffleri, are distinctly different morphologically, and the latter is a poorly known microendemic taxon of the Mexican Pacific humid tropical forest in the Sierra Madre del Sur. We used both nuclear (nDNA) and mitochondrial DNA (mtDNA) to evaluate the genetic variation of D. sanctithomae in Mexico, and complemented this with a quantitative analysis of phenotypic traits. We also conducted analyses of environmental niche models to test the hypothesis of niche differentiation of D. s. sheffleri from other taxa of D. sanctithomae. Our phylogenetic reconstructions of mtDNA consistently recovered D. s. sheffleri and D. s. sanctithomae as reciprocally monophyletic, while they shared alleles of nDNA. These mtDNA differences are comparable with differences reported between other Dendrocolaptes sister-taxa pairs. Our analysis of phenotypic traits also indicated that the taxa differ in measurements of hallux and feather barring. In contrast, niche differentiation tests suggest that the niches of both taxa are more similar than expected by chance. Our evidence leads us to propose species status for D. sheffleri. This is an additional example of recent speciation in Mexico that indicates active and peripatric evolutionary differentiation in the northern Neotropics.
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Los procesos ecológicos determinísticos son fundamentales en la estructuración del ensamblaje de aves del complejo volcánico de Colima, el cual destaca por su alto endemismo, migración y recambio taxonómico, además por su actividad volcánica, gradiente altitudinal y tipos de vegetación. El objetivo de este trabajo fue describir la diversidad de aves del complejo volcánico de Colima y los mecanismos ecológicos y biogeográficos que estructuran su composición, a partir de datos de incidencia y variables ambientales. Los resultados muestran que el riesgo volcánico, la altitud y la orientación cardinal son las variables explicativas de los patrones de riqueza. Se registraron 397 especies de las cuales 248 (62.5%) son residentes, 149 (37.5%) son migratorias y 89 (22.4%) tienen alguna categoría de endemismo. Existe una alta disimilitud (βSOR = 0.907), causada por un alto recambio de especies (βSIM = 0.749). La afinidad biogeográfica mejor representada es el dominio mesoamericano con 41-47% de las especies residentes. Se concluye que los procesos ecológicos y biogeográficos son los que estructuran a la avifauna regional y se provee un primer acercamiento a la comprensión de la actividad volcánica como un mecanismo activo en la dinámica biológica regional.
La diversidad taxonómica y funcional de un ensamblaje de aves está determinada por diversos procesos ecológicos y evolutivos. Conforme se establecen las especies, las condiciones bióticas y abióticas cambian configurando el proceso de sucesión o colonización. En ocasiones, estos procesos son alterados por eventos catastróficos que impactan de formas diversas a las especies funcionando como filtros ecológicos. En este trabajo se realiza una revisión bibliográfica sobre el disturbio volcánico como agente de perturbación que inicia procesos de sucesión ecológica en los ensamblajes de aves. Se analiza el impacto de estos fenómenos naturales sobre otros taxones y se construye una hipótesis sobre las posibles afectaciones y el proceso de sucesión que rige a las aves. Se concluye que hay un patrón en el filtro ecológico causado por el disturbio volcánico, inhibiendo principalmente a las especies que se alimentan de recursos vegetales como las granívoras, nectarívoras y frugívoras, mientras que facilita la incorporación de las especies carroñeras. La relación del ensamblaje de aves con los efectos de las erupciones volcánicas es un tema poco estudiado y con gran potencial para la investigación.
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