Structural Connectivity Predicts Functional Connectivity for Fishes in Fragmented Dendritic Ecological Networks

Streams represent dendritic ecological networks (DENs) characterized by bifurcating chains of habitat through which fishes disperse.  Fragmentation of streams in which dispersals is completely or partially blocked has the potential to negatively influence the distribution of stream fishes and predictive approaches regarding the influence of barrier manipulation are needed.  Habitat availability measures such as the recently developed Dendritic Connectivity Index (DCI) aid in predicting ecological responses to changes in stream connectivity, but application and suitability of such approaches remain largely untested.  We utilized a neutral landscape approach to model the relationship between structural connectivity (quantified using the DCI) and dispersal patterns of fish in both idealized and realistic riverine landscapes.  Preliminary results suggested variance in fish distribution among stream segments negatively correlated with the DCI in the neutral riverscape network when barriers were assigned a uniform permeability of 0.5 (R² = 0.99, P < 0.01), and the relationship persisted when permeability was decreased to 0.25 (R² = 0.96, P < 0.01).  Our findings suggest structural connectivity measured as the DCI predicts functional connectivity of fish populations measured as variability in distribution among stream segments, and the relationship is robust with regard to permeability of barriers.