Sistemática e história natural de anfíbios anuros das nascentes dos rios Samã e Miang em áreas de altitude do Escudo da Guiana em Roraima (amphibia, anura)

Abstract

In studies of faunal distribution it is coherent to adopted regions naturally delimited, because allow us to better interpret results, besides generate more secure data on biological differentiation. In Roraima such studies can, depending of the research question, insert the geographic unit of the study inside the Guiana Shield, an old geological formation covering part of Colombia, Venezuela, French Guiana and North Amazonia. In this study on systematics and distribution of anurans amphibians, in regional and general scales covering various vegetal formations, the geographic unit of the study refers to the headwaters of the rivers Samã and Miang, both located in altitudinal areas of the Guiana Shield in Roraima, in a region that makes the transition among the Brasilian Boa Vista Basin, the region of lavrado, and the Venezuelan Gran Sabana, the tepuyes region. As the geographic unit of the study is inserted in the Guiana Shield, the premisse is that its anurofauna is associated to that formation – most of the species, more than 50%, will have its occurrence restricted to this geological formation. The operational hyppothesis makes the counterpoint: there is no such restricted or endemic in the Guiana Shield. In this geographic unit of the study were registered 26 species distributed in 8 families: Hylidae 6 genera and 11 species, Leptodactylidae 3 genera and 6 species, Bufonidae 2 genera and 4 species; Allophrynidae, Centrolenidae, Craugastoridae, Microhylidae e Ranidae one species each. In the Guiana Shield occur 270 anuran species, of those 145 are said to be endemics and only two registered in the study falls in that endemism – Elachistocleis surinamensis and Hypsiboas benitezi. By this one can conclude that there is no such endemic anurofauna in the Guiana Shield in the headwaters of the sampled rivers of the present study, besides all the 24 identified species occur in the area of the Shield – two of the genera Pristimantis and Vitreorana are new species. At least 12 species are restricted to the Amazonia and North of South America, including those two falling as endemic (A. ruthveni, R. guttatus, R. margaritifera, R. merianae, H. boans, H. benitezi, O. taurinus, A. andreae, L. bolivianus, L. knudseni, E. surinamensis e S. wandae). In relation to the other 14 species, 12 are widely distributed and 2 are new. With respect to the natural history, there are brief peaks where all the population are exposed by one or two days after havy rains (Phyllomedusa, Allophryne, Trachycephalus, Elachistocleis e Vitreorana), and the reproduction of the other 22 species is continuous along all the rains period. With respect to the clutches and tadpole development there are nine variations among spawning in the floor, on the water and on the trees. With respect to the individual abundance per species Pristimantis sp., H. benitezi e H. multifasciatus were more abundant and more frequent, followed by H. geographicus, O. taurinus e L. fuscus.