Current invasive species research being conducted at MSU
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Project 11

Project Title: Evolution of Trophic Linkages in an Invaded Food Web
Investigators: Andrea L. Jaeger, Andrew G. McAdam, and Scott D. Peacor
Contact: Andrea L. Jaeger (jaegeran@msu.edu)

Abstract: One of the greatest threats to ecosystems is exotic species invasion. While the ecology of exotic species is well studied, the importance of evolutionary processes to species invasions has only recently gained prominence. Adaptive evolution results from natural selection acting on heritable traits. For traits to evolve, genetic (i.e. heritable) variation must be phenotypically expressed and result in the differential survival and reproduction (i.e. selection) of an organism. A recent wave of species invasions in the Laurentian Great Lakes of North America and surrounding inland lakes, including the predaceous zooplankton Bythotrephes longimanus, offers the opportunity to rigorously examine the evolutionary effects of species invasions. Bythotrephes has a distinctive morphology featuring a prominent tail spine, which can function as a deterrent against gape-limited fish (<100mm length) predation. Gape-limited fish predation is strong in the invaded range of Bythotrephes, thus it is likely that Bythotrephes spine morphology experiences intense selection pressure, yet, the evolutionary potential of this important exotic species remains unstudied. Bythotrephes is also particularly well suited to evolutionary studies because it is a cyclic parthenogen that annually undergoes multiple generations of asexual reproduction culminating in one generation of sexually reproduced diapausing eggs. Our research investigates the effects of rapid evolutionary change in Bythotrephes on its food web interactions. We hypothesize that differences in selection pressures between the native and invaded ranges of Bythotrephes has resulted in the evolution of spine morphology since invasion. To investigate this hypothesis, during summers 2007 and 2008 we will quantify phenotypic and genetic variation (i.e. heritability) in tail spine length of Great Lakes and inland lake Bythotrephes from contemporary populations. Second, we will quantify the strength of natural selection on Bythotrephes morphology, and will use the estimates of heritability and selection to estimate the evolutionary response of Bythotrephes morphology. Third, we will compare the evolutionary prediction against observed changes in Bythotrephes morphology since arrival in North America by resurrecting Bythotrephes from sediment cores in winters 2007 and 2008. Finally, during summer 2009 we will determine the consequence of predatory adaptations in Bythotrephes and antipredatory adaptations in Daphnia mendotae, a primary prey of Bythotrephes, for food web dynamics using a series of predation experiments pairing historical and contemporary individuals resurrected from sediment cores. This research will provide novel insight into the effects of Bythotrephes invasion in the Great Lakes and surrounding inland waters, as well as advance our current understanding of the evolutionary effects of exotic species invasion on our valued ecosystems.

For more information:
Andrew G. McAdam: http://www.fw.msu.edu/people/McAdam/Index.htm
Scott D. Peacor: http://www.msu.edu/~peacor/
NOAA Great Lakes Environmental Research Laboratory: http://www.glerl.noaa.gov/
Great Lakes Fishery Commission: http://www.glfc.org/