Meeting Abstract

38.6  Jan. 5  A climate-based model of winter energy consumption to examine the southern range limit of the goldenrod gall fly (Eurosta solidaginis) on late goldenrod (Solidago gigantea) IRWIN, J.T.*; DIDRICKSEN, D.J.; REILLY, B.W.; ABRAHAMSON, W.G.; Central Washington University, Ellensburg, WA; Central Washington University, Ellensburg, WA; Central Washington University, Ellensburg, WA; Bucknell University, Lewisburg, PA irwinj@cwu.edu

The goldenrod gall fly, Eurosta solidaginis, is a gall-inducing insect that has diverged into two reproductively isolated and genetically differentiated host races on its host plants Solidago gigantea and S. altissima. Both host plants range from Ontario to Florida in eastern North America. Flies of the altissima host race are found virtually everywhere that its host plant is present, but gigantea flies are only present in the northern tier of its host�s range. We performed a series of experiments to identify factors restricting the gigantea host race to northern locales. Correlation analysis suggests that the southern limit of gigantea flies is constrained by warm winters, likely because warmth increases energy consumption. Gigantea flies are smaller and less fecund because S. gigantea senesces earlier (thus ceasing feeding earlier in the autumn) than does S. altissima. Being smaller, the gigantea host race has less energy to support metabolism during winter and egg production the following spring. We will present our ongoing efforts to produce a model of winter energy use for goldenrod gall flies across their range, and consequent range limitations. Our work provides a model for predicting shifts in geographic distributions with global climate change.