An understanding of how environmental factors relate to the characteristics of organisms in ecological communities can help reveal important processes driving patterns of diversity. Functional traits associated with feeding, habitat use, or reproduction can be examined along environmental gradients to investigate how habitat variables influence community composition at multiple spatial scales. In this study, such an approach will be used to compare fish communities along a longitudinal gradient in the RÃo Grijalva, a large tropical river basin in southern Mexico. Functional traits of fishes will be examined along with a suite of environmental variables in study sites across a range of habitats, from upland tributary streams to broad, lowland lagoons. The diversity of traits is expected to increase from upstream to downstream as habitats become less environmentally harsh and food resources are more plentiful.
This research has important implications for conservation in this study region and in other tropical rivers. Few studies have examined changes in tropical fish communities at the scale of an entire watershed, and little is known about how environmental differences affect functional traits. A focus on how environmental factors influence fish communities will provide valuable information for evaluating the effects of species introductions, impoundments, and other forms of habitat degradation.
