Study provides insights into how climate change might impact species’ geographic ranges

University of Notre Dame News: A new study by a team of researchers led by Jessica Hellmann, assistant professor of biological sciences at the University of Notre Dame, offers interesting insights into how species may, or may not, change their geographic range — the place where they live on earth — under climate change. The lead author on the paper is recent Notre Dame doctoral degree recipient Shannon Pelini.

…In a paper appearing in this week’s edition of the Proceedings of the National Academy of Sciences (PNAS), Hellmann and her team describe how they tested the assumption that populations at the northern edge of a species’ range will increase with warming and thereby enhance the colonization process by using two butterflies: the Propertius duskywing and the Anise swallowtail.

….Hellmann pointed out that by comparing and contrasting two distinct butterfly species in the same geographic area, researchers can obtain general principles to help predict if species will change their geographic ranges under climate change.

Hellmann and her colleagues found that populations at the northern range edge in both butterfly species experienced problems when exposed to warmer conditions — the conditions that they will experience under climate change. The duskywing performed well in the summer months, initially suggesting that populations could increase with warming conditions. However, it performed poorly under warmer winter conditions, which would likely offset the summer population gains. Additionally, range expansion of the species is inhibited by the lack of host plants.

Northern populations of the swallowtail did not benefit from any of the warming treatments. The species fared badly during heat waves occurring during the summer months when tested under field conditions and fared no better under conditions of steady, moderate warming in the laboratory. Temperatures at the northern edge of the geographic range also impacted the host plant the species relies on, implying that interactions among species could change under climate change.

The results shed doubt on the assumption that populations near the upward range boundary are pre-adapted to warming and will increase with upward range expansions and this paper is the first based on experiments to say so....

Anise Swallowtail on the San Francisco Bay Trail in Tiburon, California, shot by Stephen Lea, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2