Expanding forests in the Canadian Rocky Mountains are slowly isolating groups of alpine butterflies from each other, which may lead to the extinction of the colourful insects in some areas, says a new study from the University of Alberta.

A rising tree line in the Rockies due to global warming, and a policy not to initiate "prescribed burns" (intentionally started, controlled fires) in order to manage forest growth, has created the tenuous condition for the alpine butterflies, said Jens Roland, a biological scientist at the University of Alberta.

The alpine Apollo butterfly (Parnassius) inhabits open meadows because they, like other types of butterflies, need sunlight to generate enough body heat in order to fly, and forests are generally too shady for them and inhibit their ability to move.

However, expanding forests are pinching off the Parnassius from their neighbors in nearby meadows.

"The risk of local extinction and inbreeding depression will increase as meadows shrink, the population sizes decrease and the populations become more isolated," Roland said.

"The gene pool of this species is getting more and more fragmented, and gene flow is reduced, which means these populations are more vulnerable," he added.

One particularly cold winter or summer season may be enough to wipe out an entire meadow of Parnassius, said Roland, who is the lead author of a paper on this research that appears today in the Proceedings of the National Academy of Sciences.

Roland also said the Parnassius are not currently a threatened species, but they and smaller species native to Rocky Mountain meadows, including some insects and rodents, will suffer "several consequences" if forests continue to expand unchecked.

"Often forest management practice is led by the needs of larger species, such as mountain sheep, elk and grizzly bears, while the interests of the smaller species, such as butterflies, are ove
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Contact: Ryan Smith
ryan.smith@ualberta.ca
780-492-0436
University of Alberta
13-Aug-2007