The effect of matrix structure on gene flow between Rana sylvatica populations

Historically, dispersal studies have assumed a simple structure of the landscape, with patches of suitable habitat surrounded by an uninhabitable matrix and connectivity between populations only dependent upon the distance between populations. However, in reality, landscapes are complex and may show varying degrees of permeability to different organisms. As a result, variation in the matrix can account for a greater proportion of the variability in genetic differentiation between populations than can a model of Isolation by Distance alone. To assess the effects of habitat fragmentation on the connectivity of populations, we compared the genetic structure and patterns of gene flow between sets of fragmented and unfragmented populations of wood frogs (Rana sylvatica). We expected that in the unfragmented habitat, patterns of gene flow would best be explained by an Isolation by Distance model, whereas in the fragmented habitat, incorporation of matrix structure would improve our ability to model these patterns. The affect of matrix structure on gene flow patterns was modeled using least-cost path analysis. Each habitat type was assigned a relative resistance level, which was used to calculate the path of least resistance between populations. This path was then compared to the null model of isolation by distance using microsatellite data. Preliminary results show a pattern of Isolation by Distance between populations in the unfragmented habitat (p < 0.01). In order to accurately model dispersal between populations, it may therefore be important to include the effects of the matrix on population connectivity.