Mar. 26, 2001 While it makes intuitive sense that corridors would benefit wildlife living in fragmented habitats, the evidence that animals actually use corridors is limited and ambiguous. Now genetic evidence shows that red-backed voles use existing corridors to move between forest fragments, according to new research in the April issue of Conservation Biology.
This is the first genetic study showing that animals use corridors.
"Our results show that for habitat specialists, forest corridors increase gene flow between populations relative to isolated patches," says lead author Stephen Mech, who did this work at Washington State University in Pullman, Washington, and is now at the University of Memphis in Memphis, Tennessee. Mech's co-author is James Hallet of Washington State University in Pullman, Washington.
Mech and Hallet assessed corridor use in a managed forest near the Pend Oreille River in northeastern Washington state that, like much of the land in the Pacific Northwest, is a mix of closed-canopy, clearcut and regenerating areas. To test corridor use, the researchers determined the genetic relatedness of (and so gene flow between) animal populations living in pairs of closed-canopy sites. There were three types of site pairs: they were either both in continuous closed-canopy, connected by a corridor of closed-canopy, or isolated by a clearcut or young regenerating stand. The distance between site pairs ranged from about 1500 to 4000 feet, and the corridors were up to about 500 feet wide.
Mech and Hallet found that corridors did increase gene flow in red-backed voles: populations connected by a corridor were more related to each other than those that were isolated. However, populations were even more related to each other in continuous closed-canopy, showing that corridors do not completely connect populations. This makes sense because the voles are habitat specialists that prefer closed-canopy forest.
In contrast, the researchers found that gene flow did not vary with habitat type in deer mice: populations in all three types of site pairs were equally related to each other. Likewise, this makes sense because deer mice are habitat generalists that thrive in all three types of habitat studied.
Because forest corridors increased gene flow between vole populations, Mech and Hallet conclude that corridors can help connect populations of habitat specialists. This suggests that managers should preserve corridors of forest when planning timber harvests.
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