A landscape genetic analysis of swamp rabbits (Sylvilagus aquaticus) suggests forest canopy cover enhances gene flow in an agricultural matrix

Leah K Berkman,Clayton K Nielsen,Edward J Heist,Charlotte L Roy

doi:10.1139/cjz-2017-0116

Leah K Berkman, Clayton K Nielsen + Show 2 more

Open Access

https://doi.org/10.1139/cjz-2017-0116

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Abstract

Habitat loss and fragmentation pose a continued and immediate threat to wildlife and create a persistent need for ecological information at the landscape scale to guide conservation efforts. Landscape features influence population connectivity for many species and genetic analyses can be employed to determine which of these features are most important. Because population connectivity through dispersal is important to the persistence of swamp rabbits (Sylvilagus aquaticus (Bachman, 1837)) at the northern edge of their range, we used a landscape genetic approach to relate gene flow to landscape features that may impact dispersal success. We tested resistance values for attributes of land cover, watercourse corridors, canopy cover, and roads and used causal modeling and redundancy analysis to relate these representations of landscapes to genetic distance for swamp rabbits in southern Illinois, USA. Models that included canopy cover had the strongest correlations with genetic distance and were supported by our methods whereas other models were not. We concluded that high tree canopy cover enhances gene flow and landscape connectivity for swamp rabbits in southern Illinois. Our study provides important empirical evidence that landscape variables may impact the habitat connectivity of swamp rabbits. Preserving dispersal routes for swamp rabbits should focus on improving canopy cover, in both bottomland and upland, to connect suitable habitat.

Highlights

Suitable habitat is often patchily distributed on the landscape, especially for habitat specialists and species of conservation concern (Hilty et al 2006)
All sites known to be occupied in previous surveys (Kjolhaug et al 1987; Porath 1997; Woolf and Barbour 2002; Scharine et al 2009) or predicted to have highly suitable habitat for swamp rabbits based on models (Robinson et al 2016) were trapped or surveyed for fecal pellets at least once during December–March 2004–2011
All surfaces were significantly correlated (P < 0.05) with genetic distance after accounting for physical distance in a partial Mantel test and the equal cost was not significantly correlated (P > 0.10) after accounting for the tested surface (Table 3). This means that all surfaces that were considered passed all diagnostic tests of the first step of causal modeling

Summary

Introduction

Suitable habitat is often patchily distributed on the landscape, especially for habitat specialists and species of conservation concern (Hilty et al 2006). For such patchily distributed species (e.g., metapopulations; Levins 1969), successful colonization of suitable habitat patches is critical to long-term population viability. The likelihood of successfully accessing and colonizing suitable habitat patches, in turn, relates to factors affecting dispersal (Gustafson and Gardner 1996) and is referred to as landscape connectivity (Taylor et al 1993). Understanding and maintaining landscape connectivity (Fahrig and Merriam 1994) is of paramount importance for conservation of fragmented populations and patch-dependent species.

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