Ayres Abstracts

Ungerer, M.J., M.P. Ayres, and M.J. Lombardero. 1999. Climate and the northern distribution limits of Dendroctonus frontalis Zimmermann (Coleoptera: Scolytidae). Journal of Biogeography 26:1133-1145. Full text in pdf.

Abstract.  The southern pine beetle, Dendroctonus frontalis is among the most important agents of ecological disturbance and economic loss in forests of the southeastern United States. We combined physiological measurements of insect temperature responses with climatic analyses to test the role of temperature in determining the northern distribution limits of D. frontalis. Laboratory measurements of lower lethal temperatures and published records of mortality in wild populations indicated that air temperatures of--16° should result in almost 100% mortality of D. frontalis. The distribution limits for D. frontalis approximate the isoline corresponding to an annual probability of 0.90 of reaching -16°C. Thus, D. frontalis have been found about as far north as they could possibly occur given winter temperature regimes. At latitudes from 39° N (southern Ohio) to 33° N (central Alabama), winter temperatures must exert high mortality on D. frontalis populations in at least 1 year out of 10. In contrast, we reject the hypotheses that summer temperatures or the distribution of host trees constrain the northern distribution of D. frontalis. Because of the short generation time of D. frontalis, its high dispersal abilities, and the cosmopolitan distribution of host trees, changes in either the mean or variance of minimum annual temperatures could have almost immediate effects on regional patterns of beetle infestations. We estimate that an increase of 3°C in minimum annual temperature could extend the northern distribution limits by about 170 km. The scenarios that most relaxed climatic constraints on D. frontalis involved an increase in minimum annual temperatures combined with either an increase or decrease in the interannual variance. Results emphasize the ecological importance of spatial and temporal variability in minimum annual temperatures. The physiologically based models provide a tool for guiding land management decisions in forests of the eastern United States and illustrate a general approach for predicting the regional effects of climatic patterns on the distribution of organisms.

Keywords: Dendroctonus frontalis, lower lethal temperature, distribution, Southern forest, Geographic Information System, Global change.


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