Evaluating functional connectivity with matrix behavior uncertainty for an endangered butterfly
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Understanding animal responses to landscape elements helps forecast population reactions to changing landscape conditions. The challenge is that some behaviors are poorly known and difficult to estimate. We assessed how uncertainty in behavioral responses to dense woods, an avoided landscape structure, impacts functional connectivity among reproductive habitat patches for Fender’s blue butterfly, an endangered prairie species of western Oregon, USA. We designed a factorial simulation experiment using a spatially explicit individual-based model to project functional connectivity for female butterflies across current and alternative landscapes. We varied the probability of dense woods entry and turning angle standard deviation for movements within the dense woods over a range of biologically reasonable and observed values. Butterflies in the current landscape (46 % dense woods) and one with prairie encroached by forest (60 % dense woods) showed reductions in functional connectivity estimates consistent with the expectations of habitat fragmentation. Although dense woods entrance uncertainty impacted functional connectivity projections, uncertainty in the dense woods turning angle standard deviation had comparatively little impact on connectivity estimates. Reduction and reconfiguration of the current dense woods to 27 % cover (restored landscape) appeared to facilitate a corridor behavior in dispersing individuals, likely providing a functional connectivity estimate comparable to the historic landscape (<5 % dense woods). Our simulations suggest that additional study of butterfly movement within the dense woods is unnecessary and that a partial reduction in dense woods would be sufficient to achieve historic levels of functional connectivity for Fender’s blue across the study landscape.
KeywordsHabitat fragmentation Functional connectivity SEIBM Biased correlated random walk Matrix configuration Habitat restoration
We thank the Cardwell Hills private landowners (Charlie and Rich Clark, PK and Dai Crisp, Karen Fleck-Harding, Lorin and Josh Lidell, William Pearcy, and Amy Schoener) for enabling the study of Fender’s blue butterflies on their properties. Without their help, cooperation and commitment to conservation this research would not have been possible. We thank Elizabeth Crone for helpful conversations and feedback throughout the project, two anonymous reviewers and C. Vos provided thoughtful comments that improved this manuscript. This project was financially supported by the US Fish and Wildlife Service, Strategic Environmental Research and Development Program (SERDP), Washington State University Vancouver, the Natural Science and Engineering Research Council of Canada Discovery Grant and the Canada Research Chair program.
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