Fatores determinantes dos padrões de distribuição e densidade de Allobates sumtuosus (Dendrobatidae) e Atelopus spumarius (Bufonidae) em duas bacias de drenagem em uma área de floresta de terra-firme na Amazônia central

Abstract

Species-distribution models based on remote sensing data may be useful to support conservation decisions at wide geographical scales. However, they may be inadequate for planning conservation zones within small reserves because many species occur patchily within the broad envelopes defined by such models. I investigated the spatial distributions of two frog species of conservation concern, Allobates sumtuosus and Atelopus spumarius, within a 64 km2 reserve in Brazilian Amazonia. I undertook visual and acoustic surveys in 40 riparian plots distributed throughout the two major drainages basins in Reserva Ducke, on the outskirts of Manaus, from January to March 2013. Each species was totally or largely confined to only one or other of the major drainage basins within the reserve. The drainages differ in environmental variables, such as stream pH and the density of connected and isolated pools. The differences in abiotic characteristics of drainages are associated the limited distributions of the frog species. Within drainages, distributions are also affected by stream discharge. The density of Allobates sumtuosus was negatively affected by stream pH and stream discharge and positively influenced by the number of isolated pools. The occurrence of Atelopus spumarius was associated with streams with intermediated discharge, pH near neutral and many pools connected to the stream. Very large reserves will probably contain sufficient landscape heterogeneity to accommodate most species. However, due to strongly patchy distributions, in situ studies using fine-scale species distribution models will be necessary to assess the adequacy of reserves with few square kilometers in Amazonia for the conservation of anurans.