Assessing environmental influences on gene flow for a migratory ungulate in a fire-prone landscape

Context

Migratory species traverse long distances across complex landscape mosaics. Shifts in environmental attributes across space and time could affect movement paths and genetic connectivity of migratory species.

Objectives

We identified boundaries to genetic connectivity based on population structure and evaluated environmental influences on gene flow in a migratory ungulate. We projected how genetic connectivity might be affected by actual wildfire events.

Methods

We collected over 168,400 GPS locations for 97 bighorn sheep (Ovis canadensis) and estimated kinship with 5,140 single nucleotide polymorphisms for 95 individuals. We identified subpopulations and employed machine-learning optimization to evaluate how environmental attributes affect gene flow between them. We projected future genetic connectivity based on recent landscape changes.

Results

We observed that water bodies and > 70% canopy cover may limit effective dispersal, suggesting that shifts in these landscape attributes, influenced by climate and vegetation management, may affect future gene flow. We also predicted recent wildfire events will change gene flow between three subpopulations, predicting more flow where fire reduced canopy cover at a pinchpoint near a linear lake and less flow where fire was internal to the subpopulation.

Conclusions

Modifications in canopy cover could be applied to facilitate or impede connectivity and gene flow, depending on management goals. Large, semi-linear lakes could form movement barriers in other bighorn populations. Recent wildfires will likely increase gene flow between semi-isolated subpopulations, with implications for disease management. As wildfire and tree encroachment and densification increase, gene flow between other spatially structured populations in similar landscapes may shift.