RESUMO
The Mesoamerican slider Trachemysvenusta is endemic to Central America and Southern Mexico. Several human-mediated disturbances, including habitat degradation and illegal hunting for food, have impacted its populations along the Usumacinta river basin. The extent to which these disturbances have affected the genetic diversity and population structure of T. venusta inhabiting the basin remains unresolved. To this end, we analyzed eight microsatellite markers in five wild populations of T. venusta from the middle and lower reaches of the basin as well as one captive population. Our results show high levels of genetic diversity for all analyzed populations, low F ST values, high gene flow and no genetic structure, indicating an absence of genetic differentiation across sites and, thus, a single panmictic population for the basin. Evidence of a genetic bottleneck was observed in two of the wild populations (and the captive one), indicating some impact from disturbances, whether from poaching or habitat fragmentation, despite the seemingly high connectivity of most populations. Results are discussed in terms of the relative importance of genetic parameters for the conservation of T. venusta, particularly in light of the importance of demographic stochasticity in local conditions undergoing rapid changes.
Assuntos
Distribuição Animal , Variação Genética , Repetições de Microssatélites , Tartarugas/genética , Animais , Animais Selvagens , Animais de Zoológico , Teorema de Bayes , DNA/genética , México , Rios , Tartarugas/fisiologiaRESUMO
The Central American River Turtle (Dermatemys mawii) is an endangered species that has been poorly studied. There are no reports on their population status, habitat condition, and the species distribution area is still unknown. This study analyzes the seasonal and spatial variations of their habitat and the presence/absence of D. mawii in three rivers within the Pantanos de Centla Biosphere Reserve (Tabasco, Mexico). For habitat characterization, natural segmentation of rivers was used and three sites per segment were identified, 9 in each rivers (Grijalva and Usumacinta) and 6 in Tabasquillo. Additionally, the evaluation of 11 environmental variables such as water hydrological, physicochemical characteristics and riparian and hydrophytic vegetation were carried out during two different seasons (dry and rainy). The presence/absence of species was assessed with eight fike nets that were set per segment, with a capture effort of 384 hours per trap. The capture per unit effort (CPUE) was used as an indicator of relative abundance. The results indicated spatio-temporal variations in habitat characteristics and the presence of environmental gradients. The principal components analysis (PCA) applied allowed us to determine that the first three components explained 67.8% of the environmental variability. The species presence was confirmed in all rivers, however significant differences exists in their relative abundance: the highest was registered in the Tabasquillo River where the species was present in both seasons and in all segments. Of the 11 environmental variables analyzed, the gradient, shelter and depth were the most indicative of species presence. The obtained results evidenced the importance of riparian vegetation as habitat for Dermatemys. This represents the first approach towards an action plan for a species and its habitat protection within the Pantanos de Centla Biosphere Reserve.
Assuntos
Ecossistema , Tartarugas/classificação , Animais , Conservação dos Recursos Naturais , México , Densidade Demográfica , Dinâmica Populacional , Análise de Componente Principal , Estações do Ano , Conglomerados Espaço-Temporais , Tartarugas/fisiologiaRESUMO
Presence and spatio-temporal habitat characterization of Dermatemys mawii (Testudines: Dermatemydidae) in the Grijalva-Usumacinta watershed, Tabasco, Mexico. The Central American River Turtle (Dermatemys mawii) is an endangered species that has been poorly studied. There are no reports on their population status, habitat condition, and the species distribution area is still unknown. This study analyzes the seasonal and spatial variations of their habitat and the presence/absence of D. mawii in three rivers within the Pantanos de Centla Biosphere Reserve (Tabasco, Mexico). For habitat characterization, natural segmentation of rivers was used and three sites per segment were identified, 9 in each rivers (Grijalva and Usumacinta) and 6 in Tabasquillo. Additionally, the evaluation of 11 environmental variables such as water hydrological, physicochemical characteristics and riparian and hydrophytic vegetation were carried out during two different seasons (dry and rainy). The presence/absence of species was assessed with eight fike nets that were set per segment, with a capture effort of 384 hours per trap. The capture per unit effort (CPUE) was used as an indicator of relative abundance. The results indicated spatio-temporal variations in habitat characteristics and the presence of environmental gradients. The principal components analysis (PCA) applied allowed us to determine that the first three components explained 67.8% of the environmental variability. The species presence was confirmed in all rivers, however significant differences exists in their relative abundance: the highest was registered in the Tabasquillo River where the species was present in both seasons and in all segments. Of the 11 environmental variables analyzed, the gradient, shelter and depth were the most indicative of species presence. The obtained results evidenced the importance of riparian vegetation as habitat for Dermatemys. This represents the first approach towards an action plan for a species and its habitat protection within the Pantanos de Centla Biosphere Reserve. Rev. Biol. Trop. 58 (4): 1247-1260. Epub 2010 December 01.
La tortuga centroamericana (Dermatemys mawii) es una especie en peligro de extinción pobremente estudiada. En el presente trabajo se analizaron las variaciones estacionales y espaciales del hábitat y se relacionaron con la presencia/ausencia de D. mawii en tres ríos de la Reserva de la Biosfera Pantanos de Centla (Tabasco, México). Para caracterizar el hábitat se evaluaron 11 variables (hidrológicas, fisicoquímicas del agua y de la vegetación) en dos temporadas (seca y lluviosa). Para determinar la presencia/ ausencia de la especie se colocaron 8 trampas de desvío acuáticas, empleando la captura por unidad de esfuerzo (CPUE) como indicador de la abundancia relativa. Los resultados indicaron variaciones espacio-temporales. El análisis de componentes principales (ACP) permitió determinar la variabilidad ambiental. La presencia de la especie se confirmó en los tres ríos, sin embargo la mayor abundancia relativa se registró en el Río Tabasquillo. Cuatro variables tuvieron el mayor peso como variables predictoras de la presencia de la especie. Con los resultados obtenidos, es evidente la importancia que tiene el ambiente ribereño como hábitat para Dermatemys, asimismo es posible hacer el primer acercamiento a un plan de acción para la protección de la especie y su hábitat en esta reserva.