Evol Ecol Res 11: 871-887 (2009)     Full PDF if your library subscribes.

The geographic mosaic of co-evolution and the natural enemies of Eurosta solidaginis

Michael D. Dixon1,2, Timothy P. Craig2 and Joanne K. Itami2

1Conservation Biology Graduate Program, University of Minnesota Twin Cities, St. Paul, Minnesota and  2Department of Biology, University of Minnesota Duluth, Duluth, Minnesota, USA

Correspondence: M.D. Dixon, Conservation Biology Graduate Program, University of Minnesota Twin Cities, St. Paul, MN 55108, USA.
e-mail: dixon091@umn.edu


Hypothesis: Natural enemies of a host insect that has diverged across a major biome boundary will display better survival and higher fitness on hosts from their natal biome.

Background: Eurosta solidaginis (Diptera: Tephritidae) forms galls on the goldenrod, Solidago altissima. Solidago altissima has two subspecies, one in the Great Plains and one throughout the eastern United States. Eurosta solidaginis has formed two host races, one on the prairie and one on the forest subspecies of S. altissima. These host races differ in gall size, allozyme frequencies, and morphology. An inquiline beetle, Mordellistena convicta, and a parasitoid wasp, Eurytoma gigantea, are specialist enemies of the larval stage of E. solidaginis and they also consume gall tissue. Both consume plant tissue in the gall as well. Mordellistena convicta is much more abundant in the prairie than in the forest.

Methods: We measured the abundance and mass of the parasitoid and the beetle in laboratory choice experiments, common gardens, and reciprocal transplant gardens to test for evidence of local adaptation to galls from their natal biomes.

Results: The parasitoid Eurytoma gigantea showed evidence of local adaptation consistent with the geographic mosaic of co-evolution hypothesis. The inquiline M. convicta did not show evidence of local adaptation, as both prairie and forest populations performed better on prairie galls. However, the population density of M. convicta is strongly influenced by interactions with other species that have diversified as the result of the geographic mosaic of co-evolution.

Keywords: co-evolution, oviposition preference, Solidago altissima, tritrophic interaction.

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