Microhabitat use of northern and southern flying squirrels in a recent hybrid zone

Abstract

AbstractSecondary contact of closely related species may lead to hybridization if reproductive isolation is incomplete. Selection against hybrids may become reinforced if hybrid fitness is low. This can be evident from the divergence of isolating traits. We examined habitat use of northern (Glaucomys sabrinus(Shaw, 1801)) and southern (Glaucomys volans(Linnaeus, 1758)) flying squirrels in an area of secondary contact in Ontario, Canada. We looked at summer microhabitat use within sites of sympatry and allopatry to test for evidence of reinforcement due to diverging habitat use. We also examined differences in broad-scale habitat features at woodlots to determine predictors of species occurrence across sites. We used 18 years (2002 - 2019) of flying squirrel summer capture data from 6 sites along a north-south transect. Vegetation surveys were conducted at trap locations during summer 2016 to characterize the available microhabitats within sites. Site-level habitat variables were calculated using the collected microhabitat variables. We found microhabitat variables to be weak predictors of trap-level flying squirrel presence and we found no evidence of divergence in microhabitat use over the 18 years. Further, we found latitude, not broad-scale habitat, was the strongest predictor of site-level flying squirrel occurrence. Overall, our findings suggest that microhabitat-based isolation is not being reinforced between flying squirrels; however, hybridization may be limited to areas where climate and habitat is suitable for both species.