Montane barriers to gene flow of Melanoplus bivittatus (Orthoptera: Acrididae)
1988
Baker, A.E.M. | Williams, J.S.
To determine the effectiveness of montane barriers to gene flow of the two-striped grasshopper, Melanoplus bivittatus, collections were made at four sites at the corners of a square location, each bisected by one of five Colorado mountains (total: five locations, 18 sites). The premise of this design is that samples from opposite sides of an effective barrier should have more genotypic differences than samples from the same side. Genotypic differences were measured for each grasshopper as 18 morphological measurements and six enzyme loci. Dissimilarities in morphology or enzyme loci were expressed as significant estimates of Mahalanobis squared distance (respectively, D2 or G2) between two sample sites. The presence of foothills had no influence on the number of significant G2 (age and sex classes combined) or significant D2 (age and sex classes separated). For samples near the foothills, adult females had more significant D2 than adult males. For samples near the two higher mountains, adult males had more significant D2 for site samples from opposite sides. A combination of gene flow and selection is the most plausible explanation for most of these results.
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