Ensamblajes de anuros de sistemas productivos y bosques en el piedemonte llanero, departamento del meta, Colombia

Anthropogenic habitat disturbances generate changes in the composition, diversity and abundance patterns of frogs. Due to the strict relationship with microhabitat, frogs could reflect environmental changes along disturbance and vegetation structure gradients. Between September and December 2001 we surveyed frogs in three different areas (pastures, cultivated areas, and forests) representing both dry and wet seasons at the piedemonte llanero (Meta Department savannas). We registered 247 individuals of 16 frog species (7 in pasture, 9 in cultivated areas, and 9 in forest). There was an increase in frog species richness and abundance during wet seasons, and species diversity was significantly higher during wet season in forest. As a general rule species composition and dominance fluctuated along seasons and areas. Most dominant species at the study site were Dendropsophus mathiassoni, principally at cultivated lands. Most vulnerable anurans to anthropogenic disturbance and habitat fragmentation and loss of Meta savannas were: Pristimantis medemi, Dendropsophus minutus Leptodactylus fragilis and Allobates marchesianus. Specially A. marchesianus may be particularly at risk from the synergy between sensitivity to changes in habitat and its specificity in tolerance of environmental gradients. Likewise, the absence of records of Pristimantis frater, Pristimantis savagei, Allobates juani and Allobates ranoides could indicate that production systems surrounding forest fragments remaining in the piedmont plains generate a degree of disturbance that reduces the populations of frogs that do not tolerate anthropogenic matrix. In general, relative humidity, distance to bodies of water, and the canopy coverage, influence the distribution of anurans in the mosaic of habitats in the piedmont plains. Locally to conserve these species it is important to maintain bodies of water inside forest remnants, and high canopy cover that generates a wide layer of leaf litter on the soil and environments with stable and low temperatures. It is a priority in the country to carry out detailed studies of the variables that determine the presence of anurans in microhabitat and their distribution along spatio-temporal gradients. This information not only contributes to the knowledge of the autoecology and natural history of Colombian anurans, but generates robust tools for management and conservation of these organisms in fragmented landscape.