Navegando por Orientadores "OREN, David Conway"

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Aves da Floresta Nacional do Tapajós: composição, distribuição ecológica e efeitos da exploração madeireira de baixo impacto
(Universidade Federal do Pará, 2005) HENRIQUES, Luiza Magalli Pinto; OREN, David Conway; http://lattes.cnpq.br/5451507856491990
Acesso aberto (Open Access)
Composição e biogeografia da avifauna das ilhas Caviana e Mexiana, foz do Rio Amazonas
(Universidade Federal do Pará, 1994-01-14) HENRIQUES, Luiza Magalli Pinto; OREN, David Conway; http://lattes.cnpq.br/5451507856491990
The islands of Caviana and Mexiana, located in the mouth of the Amazon River, are composed of fluvial sediments and well consolidated lands that date from the Terciary and that were separated from the continent by tectonic action at the beginning of the Holocene. The composition of the avifauna of these islands is analized both from the biogeographical and the ecological points of view. I registered 148 bird species for Caviana Island and 183 for Mexiana Island. The discrepancy between the size of the two islands (Caviana is larger than Mexiana) and the number of species observed is due to undersampling of Caviana. However, the analysis of faunal composition demonstrated that Caviana is richer in forest species than is Mexiana. In contrast, Mexiana showed a greater richness of birds of open habitats. These differences suggest that the rising of sea level at the beginning of the Holocene caused the extinction of greater part of the fauna of the understory ou Mexiana. The portions of Mexiana Island with "teso" vegetation were not submerged, maintaining their characteristic avifauna, which is also represented on Marajó Island. To analyse of the distribuitions of 157 species I subdivided the avifauna into seven categorias: widespread distribution in South America (77 species); widespread Amazonian distribution (25); distribution restricted to eastern Amazonia (7); distribution restricted to south of the Amazon River and east of the Tapajós River (3); distribution restricted to várzea (19); widespread distribution in northern Amazonia and absent from the Tocantins-Xingu interfluvium (5); and widespread distribution in Central Brasil (21). I did not find elements restricted to the Tocantins-Xingu interfluvium. This fact is related to ecological rather than historical factors. The pattern related to northern Amazonia can be interpreted as the result of recent dispersal, the system of islands at the mouth of the Amazon, or by the formation of the Purás and Gurupá Arches, which, associated with the lowering of sea level during Pleistocene, established a connection between lhe right and left banks of the Amazon River. The dispersal occurred in both directions, explaining lhe existence of a large number of species and subspecies with distributions restricted to eastern Amazonia, as well as the dispersal of Central Brasilian elements to north of the Amazon River. This last component of the avifauna is a1so related to the expansion of open vegetations, characteristic of Central Brazil, during glacial periods.
Acesso aberto (Open Access)
Composição e diversidade de espécies da anurofauna da Estação Científica Ferreira Penna, Floresta Nacional de Caxiuanã, Pará, Brasil
(Universidade Federal do Pará, 1999-08-30) BERNARDI, José Antônio Renan; OREN, David Conway; http://lattes.cnpq.br/5451507856491990
This study compares the composition of the anurofauna of the four principal habitats (terra firme forest, capoeira, igapô and aquatic vegetation) in the areas of two black water streams (igarapé Arauá and Laranjal), at the "Ferreira Penna Scientific Station" (Estação Científica Ferreira Penna (ECFPn)), located in the "Caxiuanã National Forest (FLONA de Caxiuanã)", Pará, Brazil. The samples of the areas were conduct using transects measuring 850 m in length and 10 m in width. Both areas were studied in the four periods of the year and related to annual rainfall seasonality (period of transition rainy/dry season, dry season, transition dry/rainy season, and rainy season). Shannon-Weiner índex of diversity and Jaccard index of similarity were used to compare the two areas and the habitats. Samples of anurans totalled 924 individuais belonging to 29 species distributed in 15 genera and 5 families. Hylidae was the most abundant, followed by Leptodactylidae, Dendrobatidae, Bufinidae and Pipidae. Terra firme forest showed the highest diversity. The number of species recorded was highest in the rainy season. This study and those of Ávila-Pires and Hoogmoed (1997) indicate a total of 41 species of frogs for this region, a quite high number for eastern Amazonia, reinforcing the hypothesis that the low diversity of the species of frogs normally related to this region is at least partially a result of the low number of herpetological inventories carried out up to now.
Acesso aberto (Open Access)
Variação geográfica de Osteocephalus taurinus Steindachner, 1862 (Amphibia : Anura : Hylidae)
(Universidade Federal do Pará, 2001-06) ESTUPIÑÁN-TRISTANCHO, Ruth Amanda; OREN, David Conway; http://lattes.cnpq.br/5451507856491990
Osteocephalus taurinus is an Amazonian and Orinochian nominal species with a wide geographic distribution. Its great morphologic variation has suggested that O. taurinus is in fact a species complex. This study examines the geographic variation of morphometric and morphologic characters. The species complex hypothesis is tested. Simultaneously, in order to explain the present body form distribution by biogeographic, rainfall and ecological patterns previously established for Amazonia, these patterns were assessed. From total 431 specimens studied, 16 populations were selected for analysis 20 of inner anatomic structures, 14 morphometric and 6 morphologic external characteres. Statistical analyses and isoline maps indicated that O. taurinus not is a especies complex and exist a interpopulation and intrapopulation variation on the morphometry and morphology of O. taurinus. Polymorphic anatomical characters ocurrs in this species. The first axis of a principal component analysis showed a clinal variation of body size along the entire geographic distribution was most plainly evident in males. Clinal variaton in other characters studied was independent of cline. Spatial size distribution indicated the largest specimens occur in the Amazon lands low, where rainforest vegetation divides savanna areas to the north and south of South America. These two last areas more often presented the smaller forms. In this study, the distribution observed for O. taurinus was not explained by traditional divisions of Amazonia, and suggest some noise generated by high intrapopulational variation. This spatial model of O. taurhius body size did not show a pattern of isolation by distance, which may suggest a recent arca colonization by this species. Simultaneusly, the study confirms the early Pliocenic origin hypothesis for Osteocephalus, which allowed O. taurinus had time to disperse before the Andes emerged as a geographical barrier.