Tuesday, August 5, 2008 - 3:40 PM

COS 37-7: Riverine landscapes: Exploring connectivity, extinction risk, and biogeography in an alternative geometry

William F. Fagan, University of Maryland


Riverine landscapes differ in fundamental ways from terrestrial ones. Of particular note is that the dendritic patch geometry and downstream flow of river networks leads to inherently asymmetrical opportunities for connections among parts of a landscape. My colleagues and I have been exploring what happens when spatial ecological processes such as dispersal play out in riverine systems, with a particular emphasis on understanding how these processes influence species' biogeography and extinction risks.


Here I will discuss how critical spatial features, such as branching hierarchical geometry, upstream-downstream sequencing of habitat units, and habitat fragmentation, are important to species ecology and conservation in riverine landscapes. To illustrate these points, I will discuss recent research drawing upon detailed empirical datasets for the biogeography of fishes in the Colorado and Mississippi-Missouri River systems. Results from the Colorado River dataset make clear that the degree to which a species' riverine distribution was fragmented historically is a strong predictor of the extent of extinctions that species has suffered over the last few decades.   Results from the Mississippi-Missouri River System demonstrate that considerations of river network geometry structure, coupled with a neutral metacommunity model, recapitulates important large-scale biogeographic patternsfor freshwater fish. Taken together these research projects illustrate the important contributions that riverine geometry makes to our understanding of interspecific variation in extinction risks and the potentially broad relevance of the neutral theory of biodiversity.