Exploring How the Branching Geometry of River Systems Influences Biodiversity Patterns

Principal Investigator(s): 

William Fagan

Ecologists and conservation biologists have long been interested in spatial problems such as habitat fragmentation and latitudinal gradients of biodiversity. However, much of this interest has focused on terrestrial habitat because they are the landscapes in which people live. In contrast, far less attention is paid to the spatial dynamics of river systems, which are critical for people as sources of drinking water, irrigation, and transportation.

During my time at NCEAS, I will be exploring how the branching geometry of river systems influences patterns of biodiversity, such as how many species can coexist locally, what kinds of upstream-downstream gradients in species richness exist, and how species sets differ from one watershed to another. Specific issues I'll be exploring include what happens to biodiversity patterns when new connections (such as canals) are forged between rivers and what happens when the connectivity, capacity, and dynamics of river systems are disrupted by human modifications (such as dams and withdrawals of water for irrigation).

Although most of my efforts will focus on building theoretical models and analyzing datasets on river fishes, branching geometry typical of river systems also occurs in many other contexts, including caves, hedgerows, road networks and, on a smaller scale, individual plants. Consequently, some of the results I find when studying river fishes may generalize to other systems as well.