Abstract
Corridors are frequently proposed to connect patches of habitat that have become isolated due to human-mediated alterations to the landscape. While it is understood that corridors can facilitate dispersal between patches, it remains unknown whether corridors can mitigate the negative genetic effects for entire communities modified by habitat fragmentation. These negative genetic effects, which include reduced genetic diversity, limit the potential for populations to respond to selective agents such as disease epidemics and global climate change. We provide clear evidence from a forward-time, agent-based model (ABM) that corridors can facilitate genetic resilience in fragmented habitats across a broad range of species dispersal abilities and population sizes. Our results demonstrate that even modest increases in corridor width decreased the genetic differentiation between patches and increased the genetic diversity and effective population size within patches. Furthermore, we document a trade-off between corridor quality and corridor design whereby populations connected by high-quality habitat (i.e., low corridor mortality) are more resilient to suboptimal corridor design (e.g., long and narrow corridors). The ABM also revealed that species interactions can play a greater role than corridor design in shaping the genetic responses of populations to corridors. These results demonstrate how corridors can provide long-term conservation benefits that extend beyond targeted taxa and scale up to entire communities irrespective of species dispersal abilities or population sizes.
Highlights
Agriculture and urbanization currently account for 43% of the earth’s land area (Vitousek et al 1997; Foley et al 2011; Barnosky et al 2012), and much of the remaining area is interlaced with networks of roads (Barnosky et al 2012)
The effect of population size on genetic diversity was greater at large corridor areas than at small corridor areas
The results presented here demonstrate the mitigating effects of corridors on the negative genetic effects associated with habitat fragmentation are achieved through two mechanisms: the exchange of individuals between patches and the reduction in genetic drift
Summary
Agriculture and urbanization currently account for 43% of the earth’s land area (Vitousek et al 1997; Foley et al 2011; Barnosky et al 2012), and much of the remaining area is interlaced with networks of roads (Barnosky et al 2012) These substantial disturbances to natural ecosystems and communities are projected to continue (Haberl et al 2007; Foley et al 2011) and have created a conspicuous mosaic of habitat patches embedded within a matrix of altered landscapes. The evaluation of evolutionary forces such as genetic drift and gene flow is critical for determining the long-term effects of habitat fragmentation; any resulting genetic changes will affect how populations respond to current and future agents of selection such as increased disease risk, invasive species, and global climate change (Stockwell et al 2003; Hughes and Boomsma 2004; Spielman et al 2004; Doi et al 2010; Pauls et al 2013)
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