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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Molecular Approaches to Population Structure and Bioassessment
Genetic population structuring in Nigronia serricornis (Say) (Megaloptera:Corydalidae): anthropogenic or natural influence?
J.S. Heilveil. Department of Entomology, University of Illinois, Urbana-Champaign, Illinois, USA 61820
The local extirpation of indicator species due to habitat degradation potentially restricts populations to small “islands” of suitable habitat, reducing gene flow. Reduced gene flow can cause negative impacts ranging from inbreeding depression to loss of local adaptation. In the last 20 years N. serricornis (Say) (Megaloptera: Corydalidae), an important indicator of high water quality, has disappeared from numerous sites where populations had previously been collected. Using allozymes and microsatellite markers, the population structuring of N. serricornis is being examined in order to answer two questions: First, what effect does habitat fragmentation have on the population structuring in N. serricornis? Second, are the observed patterns of population structuring more influenced by degree of anthropogenic change, or by geographic distance alone? Allozyme data from 19 loci revealed three scorable, polymorphic, loci with little population structuring (FST=0.0198). Microsatellite data (from the first megalopteran microsatellite marker) reveals a much greater level of differentiation (FST=0.63). The large disparity between allozyme and microsatellite differentiation suggests that allozymes may be under selection in this system. Microsatellite FST is large even between sites in a relatively undeveloped region (FST=0.41), suggesting that some of the population structure may pre-date anthropogenic habitat modification.
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