Community assembly and phylogenetic structure of the fish community from the upper Amazon basin

Abstract

Environmental influences on the composition and abundance of species in a region has long been study topic in ecology. The introduction of a space dimension, and an acknowledgement of the influence of spatial autocorrelation in ecological studies has greatly facilitated expanded biological pattern interpretation. Recently, the availability of phylogenies for several taxa has provided a better understanding of the regional patterns of species distribution at large spatial scales. Despite decades of investigation, there are few ecological studies of the Amazonia fish fauna that have both looked at the main factors shaping the fish assemblages in the region and used environmental, spatial and phylogenetical approaches simultaneously. The current study aimed to measure the relative influence of environmental, spatial and historical events on the fish assemblages of the upper Amazon basin. Climate, slope and elevation were used as proxies for environmental features; phylogenetic relationships were used as a proxy for historical events and watercourse was used to represent the spatial distance between sites. A strong influence by historical events was expected, since many fish assemblies are known to have been isolated in headwater regions for extended periods. The influence of both historical (or phylogeny, 22.4%) and spatial events (4.1%) was higher than the influence of purely climatic events (1.4%). In addition, the total influence of historical events (pure phylogeny, phylogeny + space, and phylogeny + climate, 41.5%) was greater than the total influence of space (19.7%) and climate (13.1%). Such patterns are most likely due to the extinction processes caused by environmental filters generated by the Andean orogeny and formation of new taxa caused by increases in sediment load in large river systems. In conclusion, our analysis indicated that historical events were the strongest drivers of the local fish composition in the upper Amazon basin.