Structure of an anuran community in a montane meadow in southeastern Brazil: effects of seasonality, habitat, and predation

Abstract

Abstract In order to assess the main factors influencing its structure, an anuran community was studied from August 1996 to July 1997, in a 1200 m high rocky meadow site at the Serra do Cipó, Minas Gerais, Brasil, a region with markedly seasonal climate. The study site included three temporary habitats: a stream, a puddle, and a swamp. Thirteen anuran species were recorded at the study site. Species of tadpoles differed in microhabitat as to their position in water column, annual occurrence period, and water flow in the occupied sites. Aquatic vegetation, depth and occupied habitat (stream, swamp, or puddle) were of secondary importance in telling species apart. Calling sites of males were distinguished based on occupied habitat and annual activity period. Most species started their reproductive activities at the onset of the rains, in an opportunistic way. Water availability in the habitat seems to be the most important factor affecting temporal distribution of reproductive activities in the anuran community. Competitive interactions could not be detected in the community. The most important tadpole predators recorded at the study site were belostomatid water bugs and dragonfly nymphs. Their abundance peaks occurred after those of tadpoles, as predicted for predator-prey populations with interconnected cycles. Mortality rates were high for tadpoles, and predation is the most likely cause. Differences recorded among species, considering time of occurrence, tadpole microhabitats, and male calling sites, may reflect distinct specific adaptations and preferences.