GENETIC EVIDENCE SHOWS ANIMALS USE CORRIDORS
PULLMAN, Washington, March 26, 2001 (ENS) - New genetic evidence shows
that some forest species make use of habitat corridors - strips of green
space that join larger patches of intact forest - to travel between
forest fragments.
The study, published in the April issue of Conservation Biology, 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,"
said lead author Stephen Mech of 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 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 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 1,500 to 4,000 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 connect populations as well as intact 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. 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.