Modelagem de ocupação e genética populacional do anuro Hylodes fredi (Hylodidae) endêmico da Ilha Grande, Angra dos Reis, Rio de Janeiro

Abstract

Amphibians are considered the most threatened group of terrestrial vertebrates in terms of species extinction. Considering megadiverse countries, where the conservation status of most species is unknown, several species of the Hylodidae family are categorized as data deficient, including Hylodes fredi, a stream-dwelling endemic frog from Ilha Grande (Angra dos Reis, Rio de Janeiro). Although different aspects of the biology and ecology of H. fredi have already been studied, none of them considered in their methods the possible bias caused by problems in the detection of the species. Furthermore, there are still no population genetics studies with Hylodes species, and there is no information on the genetic variation in H. fredi. Seeking to better understand the threat level of H. fredi and to help guide conservation efforts for the species on Ilha Grande, this thesis was divided in two chapters. The first chapter sought to better understand the factors affecting the occupation of H. fredi within the streams where it occurs. For this, the occupancy modeling approach was used on a finer scale, considering the imperfect detection. Perpendicular transects were established in six streams with known occurrence of the species, and each stream was subdivided into ten sampling plots. Single-species and single-season occupancy models were created with the UNMARKED R package, and model selection was performed. The species had an occupancy of 0.28 and detectability of 0.25. The best models suggest that H. fredi occupancy increases proportionally with the rock cover in the landscape, and inversely with leaf litter cover. On the other hand, detectability lowered with an increase in leaf litter cover and was affected by the air temperature. The results of this chapter indicate that H. fredi has a restricted and reduced occupation to streams and their nearby banks, with implications for its conservation. The second chapter uses a mitochondrial maker to perform the first population genetic study of H. fredi. This chapter mainly explores genetic variation and the possibility of genetic population structure in the species. A high haplotype diversity (Hd= 0.876) and low nucleotide diversity (Π=0.006) were found for the ND2 gene region in the species as a whole. The data suggest that H. fredi is structured in three groups, but that did not reflect the geographic aspects of the island, such as microbasins and slopes. Each genetic group found may represent a significant evolutionary unit for conservation, and their geographic distribution should be better understood. Although the results point to a high genetic variation within the species, further studies are needed using genetic markers that capture the recent evolutionary history of the species, and research that explores the displacement by females and juveniles of H. fredi in the landscape. The data reinforce the importance of not relaxing conservation efforts for the species.