Do mountain tops act as sky islands for species that live at high elevations? Are plant populations on these mountain tops isolated from one another because the valleys between them act as barriers, or can pollinators act as bridges allowing genes to flow among distant populations?
Dr. Andrea Kramer and colleagues from the Chicago Botanic Garden and the University of Illinois at Chicago were interested in pursuing these questions, particularly for a genus of plants, Penstemon (Plantaginaceae), endemic to the Great Basin region of the Western United States. They published their findings in the January issue of the American Journal of Botany (http://www.amjbot.org/cgi/content/full/98/1/109).
The flow of genetic material between populations maintains a species. In plants, if populations are separated by a landscape barrier such that pollen or seeds are unable to traverse either over or through, then the populations will begin to differ, either via mutations or genetic drift over time. However, habitat fragmentation and distance may not always be barriers, depending on the species and their modes of dispersal. And sometimes studies surprise us with their findings.
"These questions become increasingly important in places like the Great Basin as we consider the effects of climate change on native plant communities and the wildlife that depend upon them," Kramer commented. "The majority of the Great Basin region's species diversity is located on mountain tops, and as a generally warming climate drives species to higher elevations, the distance between mountaintop plant populations increases and more is required of the pollinators in order to traverse the arid valleys between them."
Kramer and her colleagues chose Penstemon because these plants provide critical resources for pollinators and other wildlife. But, as Kramer notes, "Until recently
|Contact: Richard Hund|
American Journal of Botany