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Appalachian Trechus of the vandykei Group 
are often quite abundant, exhibiting densities of about 20 to 80 individuals 
per square meter. The vandykei group is represented in the Black-Great 
Craggy and Bald mountains east and north of Asheville, and to the west 
in the Great Smoky, Newfound, Unicoi, Cheoah, Snowbird, Tusquitee- 
Valley River, and Great Balsam ranges. An apparent relict population 
occurs on Whiteside Mountain, where the Cowees meet the Blue Ridge 
escarpment. Nevertheless, some curious distributional gaps exist: Pop- 
ulations assignable to this group have not been found elsewhere in the 
Cowees, on the Toxaway Mountain spur off the Great Balsams, in the 
Plott Balsams (between the Smokies and Great Balsams), nor in the 
Nantahalas, despite special efforts to collect them there. Discontinuity is 
also found in the chain of higher peaks along the Tennessee-North 
Carolina border, with the vandykei group represented on Sandymush 
Bald and Camp Creek Bald, but not on Tennessee Bluff in between. 
Trechus taxa assignable to other species groups are relatively abundant 
in these areas where the vandykei group is absent. 
Although extensive collecting over the past quarter century has well 
established the altitudinal restriction of these isolates, such negative 
evidence does not totally preclude the possibility of some limited gene 
flow across lowlands. In fact, one specimen of T. bowlingi has been 
taken in Greenbrier Cove, in the Great Smokies, and one specimen of T. 
tusquitee was taken near Old Road Gap along the north approach to 
Tusquitee Bald, both specimens near elevations of about 900 m. Also, 
several altitudinally restricted species, including T. bowlingi , occur at 
about 950 to 1,050 m on the north (Tennessee) side of the Great 
Smokies, where cool microclimates prevail as cold air flows down from 
the crest through deep ravines. However, the rarity of specimens at 
lower elevations indicates only that minimal gene flow across lowlands 
is possible, not that it is significant. 
In this study we examine a suite of closely related Trechus taxa (the 
vandykei species group) using the technique of gel electrophoresis. This 
technique permits us to look at another set of characters, enzymatic 
proteins, thus providing data complementary to biogeographic and 
morphological considerations. Electrophoretic data are easily quantified 
and permit insight into relative degrees of biochemical differentiation. 
The underlying genetic basis of electrophoretic variation can usually be 
inferred, allowing us to determine whether or not limited gene flow 
exists between geographically and altitudinally isolated populations. 
Although most of the isolates sampled are restricted to single peaks, 
three are more widely distributed in major, continuous uplands — T. 
vandykei in the Black and Great Craggy mountains, T. bowlingi in the 
Great Smoky Mountains, and T pisgahensis in the Great Balsam 
