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T. C. Kane, T. C. Barr, Jr., and G. E. Stratton 
vandykei and longer-term isolation than had previously been postulated; 
and (2) the vandykei subgroup has a much stronger affinity with haoe, 
the similarity being most striking at the CAH locus, where both 
subgroups not only have the same two electromorphs but have them in 
very similar frequencies. Trechus haoe and T. vandykei are readily 
differentiated by morphological characters (Barr 1962); furthermore, 
they occupy the western and eastern extremes of the geographic region 
tracked by the entire vandykei group. 
It appears that the vandykei subgroup dispersed across the French 
Broad River valley by a route farther north than previously suggested, 
probably along the chain of high mountains on the Tennessee-North 
Carolina border, then south into the Blacks, Great Craggies, and 
adjacent high Blue Ridge. The electrophoretic data clearly are in accord 
with biogeographical and morphological data supporting this hypothesis; 
the only representative of Microtrechus in the northeast region other 
than the vandykei subgroup isolates is T. inexpectatus (Barr 1985b), 
described from Camp Creek Bald (CC), the first major peak encountered 
as one proceeds eastward along the Tennessee-North Carolina border 
from the French Broad River valley. Going in the opposite direction, 
from northeast to southwest across the French Broad, the first major 
peak encountered is Tennessee Bluff (Cocke Co., Tenn., and Madison 
Co., N.C.); two Trechus s. str. taxa occur on Tennessee Bluff, an 
undescribed species related to T. scopulosus (Barr 1962, 1979) and the 
only subspecies (undescribed) of the abundant, widely distributed 
(northwest North Carolina, northeast Tennessee, southwest Virginia, 
eastern West Virginia) polytypic T. ( T .) hydropicus known from the 
southwest region (Barr, in preparation). The hypothesis of an earlier, 
more remote separation of subgenus Microtrechus from Trechus s. str. 
during a period of isolation in the Unaka region west of the Asheville 
basin is thus supported not only by “center of origin” considerations but 
by additional biochemical and biogeographical data. 
More difficult to explain are the close affinities between T. haoe 
(Unicoi Mountains) and the vandykei subgroup, given that, at present, 
the range of T. bowlingi in the Great Smoky Mountains intervenes. One 
possible but speculative scenario (Barr 1985a) for evolution of the 
vandykei group includes the following sequence: 
1) An ancestral species diverged from Microtrechus by occupying 
the niche of small predator in superficial litter; among southern 
Appalachian Trechus spp., only the vandykei group isolates occupy that 
niche at present (Barr 1985a). 
2) The ancestral species split into populations in the two major 
mountain ranges of the southwest region, the Smokies (GSM) and the 
Great Balsams-Pisgah Ledge (GBM). 
