Studying the movement ecology of small or elusive species can be logistically challenging if not impossible given our current tracking technology. However, population genetics and modeling can be used to elucidate movement ecology such as migration, dispersal or connectivity. Understanding the movement ecology of species of conservation concern can be crucial for effective management. The Black-capped Vireo (Vireo atricapilla) is a recently delisted migratory passerine that has been threatened by habitat fragmentation and brood parasitism, producing fragmented populations across central Texas. Our goal was to understand Black-capped Vireo dispersal in central Texas adjacent to Fort Hood, which houses the largest and most stable population. Our research questions were 1) What are the patterns of gene flow? We genotyped 343 individuals using microsatellite and SNP loci and estimated gene flow using genetic differentiation, migration rates, and parentage assignment 2) What landscape features may influence functional connectivity between populations? We ran gravity and linear mixed models to test how landscape features influence gene flow. 3) What will happen to functional connectivity and subsequently the populations given future IPCC climate change projections? We used a spatially-explicit individual-based model to simulate the resulting gene flow based on the IPCC A1B, A2, B1, and B2 scenarios.
Results/Conclusions
Across gene flow and migration analyses, we found evidence for asymmetrical movement from Fort Hood to other central Texas sites. In concordance with demographic studies, we assert that there is a source-sink metapopulation in central Texas with Fort Hood generally acting as a source to the smaller surrounding populations. Our top gravity models, based on AIC values, indicated that agriculture impedes gene flow while wetlands associated with riverine systems facilitate gene flow. Rapid habitat fragmentation in central Texas may be an ever-growing threat to connectivity, but riverine systems could act as corridors between populations. Our spatially explicit individual based model showed that with increased fragmentation throughout central Texas, functional connectivity would decrease accordingly. With depressed dispersal between populations of a source-sink metapopulation, the sink populations could eventually go extinct without the immigration from Fort Hood. The presented results elucidate the movements and factors influencing dispersal of Black-capped Vireo populations in hopes of informing conservation efforts.