Global Warming-Induced Hybridization in Flying Squirrels

Garroway et al. write that "many species have responded to contemporary climate change through shifts in their geographic ranges," and they say that "this could lead to increased sympatry [i.e., partially overlapping ranges] between recently diverged species, likely increasing the potential for hybridization." And they further note that this phenomenon "can be positive if it increases genetic variability and creates new gene combinations that increase the potential to adapt." To test this hypothesis, between 2002 and 2004, Garroway et al. conducted more than 1600 successful live-trappings of southern (Glaucomys volans) and northern (Glaucomys sabrinus) flying squirrels throughout portions of Ontario, Canada and Pennsylvania, USA; and from the hairs of these squirrels they extracted nuclear and mitochondrial DNA, which they analyzed in ways that allowed them to obtain the following results.

It had already been determined by Bowman et al. (2005) that G. volens had expanded its range from the south beginning in the mid-1990s in concert with a series of warm winters; and now the nine Canadian and U.S. researchers' new findings indicate that "the expansion of G. volans north into the G. sabrinus range in Ontario has resulted in the formation of a new hybrid zone." In addition, their analyses suggest that "the hybridization was recent, coinciding with the recent increase in sympatry." Thus, they go on to state that -- to their knowledge -- "this is the first report of hybrid zone formation following a range expansion induced by contemporary climate change," which unique findings represent yet another way in which living organisms can both physically (by shifting their ranges) and genetically (by hybridization) successfully confront the challenges that may be presented to them by global warming.

Additional Reference
Bowman, J., Holloway, G.L., Malcolm, J.R., Middel, K.R. and Wilson, P.J. 2005. Northern range boundary dynamics of southern flying squirrels: evidence of an energetic bottleneck. Canadian Journal of Zoology 83: 1486-1494.