Corridor design and quality impact genetic resilience across populations

Although corridors are known to facilitate dispersal, what is still unknown is whether corridors can reduce the negative genetic effects of habitat fragmentation, such as reduced population size and genetic diversity due to genetic drift or inbreeding.  How does corridor quality and design affect population genetics at an ecologically relevant scale?  In their recent paper in Evolutionary Applications, Christie and Knowles examine this question by modeling a patch-corridor system using a forward-time, agent-based model that tracks individuals and their genotypes through space and time.  They focus on four illustrative species groups that differ in population size and dispersal abilities: beech trees (good dispersers, large population sizes), crickets (poor dispersers, large population sizes, foxes (good dispersers, small population sizes), and salamanders (poor dispersers, small population sizes).  They specifically look at how population genetics are affected by corridor quality, species interactions, and design properties such as corridor length and width.

They found that corridors effectively mitigate the negative effects of habitat fragmentation through the exchange of individuals and the reduction of genetic drift. As a consequence of this, increasing corridor width leads to higher overall population numbers and increases the exchange of individuals, and also facilitates the survival of offspring from a larger number of individuals.   The benefits of increased corridor width are maximized when corridor habitat quality is high, and higher quality habitat tends to support populations that are more resilient to poor corridor design (i.e. long and narrow corridors).  Positive species interactions also mitigated negative genetic effects by increasing total genetic diversity, highlighting the importance of designing corridors for entire communities rather than one focal species.  From a management and conservation perspective, the benefits of increased genetic resilience associated with corridor quality and design can have far-reaching implications for not just local populations, but communities as a whole.