Taxocenose de serpentes em ambientes aquáticos de áreas de altitude em Roraima (squamata: serpentes)

Abstract

In studies on faunal distribution it is coherent to adopt naturally delimited regions, because allow us to interpret the results with better biogeographic accuracy, and generate more secure data on biological differentiation. In all Roraima region such studies can, depending on the question, to insert their geographic units of work into the Guiana Shield, an old geologic formation comprising part of Colombia, Venezuela, French Guiana and North Amazonia – Roraima is inserted in the central area of the Shield. In this study on snakes distribution, in regional and general scale comprising various vegetal formations, the geographic unit refers to the headwaters of the rivers Samã and Miang, both located in altitudinal areas of the Guiana Shield in Roraima (04º25', 61º08'W), region that makes the transition between the Brasilian Boa Vista Basin, region of lavrado, and the Venezuelan Gran Sabana, region of the tepuyes. The operational hypothesis is that as the geographic unit of the study is inserted into Guiana Shield, its ofiofauna is endemic to this formation – most of the species, more than 50%, will have restricted occurrence to that geologic formation. It was registered in the geographic unit of the study 42 species of snakes, included in 6 families: Leptotyphlopidae 1 genera and 1 species, Boidae 2 genera and 2 species, Colubridae 8 genera and 12 species, Dipsadidae 11 genera and 20 species, Elapidae 1 genera and 3 species and Viperidae 3 genera and 4 species. In the Guiana Shield region occur 149 species of snakes, 17 are said to be endemic to the geological formation. At least 10 species registered at BV-8 in Roraima are restricted to the Amazonian domain and North of South America: Trilepida macrolepis, Chironius multiventris, Phrynonax poecilonotus, Dipsas pavonina, Dipsas variegata, Erythrolamprus breviceps, Pseudoboa neuwiedii, Xenodon severus, Micrurus hemprichii and Bothrops atrox. Two species, Dipsas copei and Erythrolamprus trebbaui have localized distribution, occurring only in some Amazon regions; 29 species have wide distribution and only Micrurus pacaraimae can be considered endemic to the study are, so far. Although the 42 registered species occur in Shield area, the distribution is wider, therefore it can be concluded that there is no such endemic Guiana Shield ofiofauna in the geographic unit of this study. With respect to the natural history, four guilds of snakes are present into the geographic unit of study, prevailing batracophagy and saurivory, followed by those that predate birds and mammals. In respect to the reproduction most species have some link to the rain season, some with more than one reproductive cycle, most of them are oviparous. The most frequent species in this study and with more specimens collected was Bothrops bilineata, which is not common in herpetological reports. Most of the species leaving in the headwaters of the rivers Samã and Miang use forested areas to survive, showing the importance of the microhabitats associated to the headwaters of these rivers.