A Tool for Understanding Gene Flow and Connectivity in Riverscapes

We introduce Cost Distance FISHeries (CDFISH), a program to simulate gene flow in complex stream networks (riverscapes) under a wide range of environmental scenarios for aquatic organisms. The spatially-explicit computer program implements individual-based population genetic modeling with age structure, Mendelian inheritance, and a k-allele mutation model on a stream network with resistance gradients to movement. The program simulates subpopulations and computes changes in parameters (allele frequencies, heterozygosity, F_ST, pairwise distance matrices) through time, employing user-defined functions of individual movement (e.g., migration), reproduction, mortality, and dispersal through straying on a continuous riverscape resistance surface. This program is a valuable tool (http://cel.dbs.umt.edu/software/CDFISH/) for the study of landscape genetics for aquatic species living in complex stream environments, and allows assessments of effects of future changes of riverscape resistance (e.g. due to climate change) on connectivity.