Influência combinada dos rios como barreira e do gradiente de inundação nos padrões biogeográficos de anfíbios e répteis Squamata no sudeste da Amazônia

Abstract

The historical search for recognition of evolutionary patterns and processes of Amazonian organisms aiming to reconstruct the evolutionary history of this mega-diverse landscape led to several hypotheses. Advances in sampling and analysis methods allowed the use of unexplored localities and organisms as a model for this search, such as amphibians and squamates. In this study, we seek to understand the integrated influence of riverine barriers and the flooding gradient in current assemblages distribution patterns of amphibians and squamates in the Middle Tapajós River region, eastern Amazonia, which is little known and threatened by imminent anthropogenic activity. For this, we detect individuals at sampling units located in all banks of the main rivers, Tapajós and Jamanxim, through active search, pitfall traps and occasional encounters in all periods of fluvial hydrological cycle. We identify the taxa with a morphological, acoustic, ecological and molecular integrative approach, detect and test the distribution patterns with uni- and multivariate ordinations, linear and piecewise regressions and analysis of variance. In total, we found 92 amphibians and 101 squamates, and 26 and seven, respectively, showed riverine barrier effect in their distribution, evidencing the Tapajós River as a possible recent barrier and the Jamanxim River as a weak barrier. Differences were found in the composition of assemblages restricted or not to riparian forests and the most affected by the riverine barrier were non-riparian amphibians and squamates, and small stream riparian amphibians. Small, diurnal terrestrial amphibians and small- medium, diurnal semi-arboricole squamates prove to be especially affected by riverine barriers, and should be priorized in further studies with this theme. The Middle Tapajós River region is evidenced as a faunistic contact zone, limiting the distribution of typical lineages of West and East Amazonian regions. The fluvial dynamics controls the distribution patterns in the region and may be affected by changes from anthropogenic activities, promoting or preventing the taxa segregation and extinguishing relevant environments, highlighting the importance to preserve this dynamics.