Genetic Patterns and Population Structure 
in Appalachian Trechus of the vandykei Group 
(Coleoptera: Carabidae) 
Thomas C. Kane 
Department of Biological Sciences 
University of Cincinnati, Cincinnati, Ohio 45221 
Thomas C. Barr, Jr. 
School of Biological Sciences 
University of Kentucky, Lexington, Kentucky 40506 
AND 
Gail E. Stratton 
Department of Biology 
Albion College, Albion, Michigan 49224 
ABSTRACT . — The genus Trechus is diverse and widespread in the 
southern Appalachian region. A majority of its species are alpine 
endemics, altitudinally restricted to elevations above 1,350 m. Five 
taxonomic subgroups of the vandykei species group of Trechus were 
examined electrophoretically to assess patterns of differentiation within 
and between taxa. Genetic differentiation within subgroups is slight to 
moderate, suggesting that gene flow between local populations is 
maintained or has only recently been interrupted. Differentiation 
between subgroups is moderate to very great, indicating complete 
genetic isolation at present. Varying degrees of affinity between sub- 
groups are consistent with the hypothesis that speciation has resulted 
from lineage vicariance caused by fluctuating Pleistocene climates. The 
vandykei group belongs to the endemic southern Appalachian subgenus 
Microtrechus, which probably originated southwest of a lowland 
dispersal barrier, the Asheville basin and the French Broad River 
valley. Electrophoretic data indicate that the vandykei subgroup has 
dispersed northeast of this lowland relatively recently. Affinities of this 
subgroup with isolates in the Great Smoky and Unicoi mountains, 
rather than the pisgahensis subgroup in the Great Balsam Mountains 
immediately south of the Asheville basin, suggest that this lowland has 
been a dispersal barrier throughout the Pleistocene and earlier. 
Dispersal of Microtrechus species east of the Asheville basin and of 
Trechus, s. str., species west of the lowland probably occurred across 
the narrow French Broad River gorge and the mountain chains along 
the North Carolina-Tennessee border. 
More than three-fourths of North American species of the carabid 
beetle genus Trechus occur in the southern Appalachians. In this region 
Brimleyana 16:133-150, July 1990 
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