Overachieving amphibians

Globally, amphibians aren't doing so well. This most endangered class of vertebrates is being hammered from all sides by a whole suite of environmental impacts. Still, there are groups and places where they're doing OK - the salamanders of the Appalachians are amphibians who're getting the job done. New research coming out in the Proceedings of the National Academy of Sciences takes a look at how they might be doing that.

The Appalachians support the greatest diversity of salamanders of any place on earth. The eastern mountains are home to 70 species, 30 in the Great Smoky Mountain National Park alone. Evan Grant, one of the researchers involved in the study makes an excellent point when he stresses that, while we're often rightly preoccupied with species that are threatened with extinction, "it is also important to look at the populations that are doing well, and to understand what makes the population or species more stable. You can apply this to interpret what might be happening with populations that are declining."

In the PNAS study, researchers marked over 2500 individuals belonging to two species of lungless salamanders (Desmognathus fuscus and D. monticola) in small streams of Shenandoah National Park (that's D. fuscus up top). While the salamanders are primarily aquatic, particularly are larvae, they are able to move over land and sometimes will travel between adjacent streams. Results indicated that, while salamanders prefer to disperse upstream, there is significant movement between streams, especially among juveniles. This movement within stream basins adds significantly to the probability of a population surviving. This is a common finding in metapopulation studies, which show that ever moderate levels of immigration between subpopulations can go a long way toward fighting the loss of genetic diversity that plague small populations.

Also of significant import on the conservation side of this study, is the significance of the terrestrial habitat between the streams. I think many of would focus our attention on the stream basins and riparian forest - this study indicates that even terrestrial areas quite distant from the stream itself may be critical in maintaining salamander diversity.