Expanding ain't easy

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Proc. Natl Acad. Sci. USA 106, 11160–11165 (2009)

Credit: JASON DZURISIN

It is often assumed that species will shift their populations poleward as temperatures rise with climate change. Now a study has tested this hypothesis for two butterflies, Erynnis propertius and Papilio zelicaon, that have an overlapping coastal distribution in North America.

A team of researchers led by Jessica Hellmann at the University of Notre Dame in Indiana switched a central population of each species with a peripheral, poleward population of the same species. For each translocation, they tested whether host plants and local climate would affect range expansion. While the peripheral population of E. propertius thrived in the relatively high summer temperatures of the central location, this benefit was probably negated by the extra energy expended under warmer winter conditions, found the researchers. In contrast, translocated peripheral populations of P. zelicaon suffered under the relatively high summer temperatures. The ability of the species to shift their populations poleward was hampered by the availability and suitability of host plants.

The study suggests that enhancing peripheral populations is unlikely to facilitate simple poleward range shifts, at least for these two butterfly species. The findings have important implications for efforts to conserve species affected by climate change.

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Heffernan, O. Expanding ain't easy. Nature Clim Change 1, 88 (2009) doi:10.1038/climate.2009.71

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