Aspectos da biologia e da dinâmica populacional em cinco espécies de dendrobatídeos (Amphibia: Anura) na Amazônia Central

Abstract

Although there exists much data about breeding behavior of dendrobatid species, there is a lack of information on other biological traits and aspects of population dynamics. Herein, I describe the variation in population structure and recapture rates of five simpatric species of dendrobatids, Colostethus caeruleodactylus, Colostethus nidicola, Colostethus sp., Epipedobates hahneli, and Epipedobates trivittatus, over four years. The study was carried out in an area of primary forest of terra firme , located at the Castanho municipality, south of Manaus, Central Amazonian. Individuals of the five species were captured and marked from august 2000 to april 2005, with aproximate monthly samplies, of two or three days. Captured individuals were measured, sexed, and toe-clipped. Colostethus females were larger than males, which is the pattern observed in dendrobatids. The number of captured individuals within an amphibian population may vary along the time, and a series of factors could be related with population fluctuation. Precipitation is an important environmental factor influencing amphibian populations, but did not influence the number of adult Colostethus captured in different years. Dendrobatids found in seasonal environments restrict their reproductive activities, such as vocalization, mating and/or tadpole transportation, to the wet season. There was seasonality in the capture of adult individuals of the five species, with the higher number of adults captured from october to may. The number of juveniles captured varied between months for the three species of Colostethus, suggesting the existence of a temporal displacement on the juvenil recruitment. The number of juveniles of Epipedobates trivittatus captured was higher than the number of adults, and the presence of juveniles with post-metamorphic sizes (<10 mm) during the whole year, indicates that E. trivittatus breed along the year. However, the number of male E. trivittatus vocalizating, in courtship with females, and transportating tadpoles was higher in wet months. In general it has been suggested that dendrobatid species reach sexual maturity in their first year of life. Likewise, our data suggest that individuals reach adult size in less than one year, mainly because juvenile average size of Colostethus increases along several months, reaching adult sizes within 6-9 months. The few studies about survival of anuran species in tropical environments, revealed a great variation in recapture rates. Recapture rates between reproductive seasons varied among the three species of Colostethus. Although low recapture rates found in Colostethus caeruleodactylus and Colostethus nidicola suggest that most individuals of those populations do not survive to the second reproductive season, Colostethus sp. has similar recapture rates to the temperate species, indicating that that most individuals of these populations survive to the second reproductive season. Besides this, recapture data suggests that migration or survival rates vary between the sexes.