149 
Appalachian Trechus of the vandykei Group 
3) The GBM population dispersed northward and southward, but 
only relict populations survive in the Newfound Mountains to the north 
and on Whiteside Mountain to the south. The GSM population, 
however, dispersed to the northeast along the Tennessee-North Carolina 
border and southwest into the Cheoah, Snowbird, Tusquitee-Valley 
River, and Unicoi mountains. 
4) In the Smokies, the extensive upland area and microhabitat 
heterogeneity (patchiness) favored colonization and speciation in other 
species groups of Trechus ; the vandykei- group isolate was subject to 
strong selection pressure for niche divergence to permit coexistence. 
Meanwhile, colonies dispersing to the northeast and southwest evolved 
less rapidly; consequently, they are more similar to each other than to 
bowlingi , the species that now occupies the Smokies. 
5) An early offshoot of the GSM population eventually colonized 
the mountains southwest of the Smokies — Tusquitee Bald, Joanna Bald, 
and Cheoah Bald. Finding only one, two, or no competing Trechus 
species, they diverged less rapidly than the GSM ancestor. Possibly they 
represent an evolutionary stage intermediate to the beetles that dispersed 
northeastward and the present-day, more derivative species now found 
in the Smokies, T. bowlingi. 
6) Meanwhile, the original GSM ancestral type crossed the French 
Broad River valley and successively colonized CC, BB, the Blacks-Great 
Craggies to the south, and finally Unaka Mountain to the northeast. A 
relict population of the southwesterly dispersal survives in the Unicoi 
Mountains as T. haoe. The two peripheral subgroups have evolved less 
(at least biochemically) than the parental populations they left behind in 
the Smokies. 
ACKNOWLEDGMENTS .— We thank William Badaracca, Judith 
Barr, and Thomas C. Barr III for assistance with the field collecting. A 
significant portion of this research was conducted at the Highlands 
Biological Laboratory, Highlands, N.C. We acknowledge the cooperation 
of the staff at Great Smoky Mountains National Park, Gatlinburg, 
Tenn., and Wolf Laurel Resort, Mars Hill, N.C., for permission to 
collect in areas under their supervison. This study was supported in part 
by National Science Foundation grants DEB-8202273 (TCK) and DEB- 
8202339 (TCB) and by a grant from the Highlands Biological Foundation 
(TCB). 
LITERATURE CITED 
Barr, T. C., Jr. 1962. The genus Trechus (Coleoptera: Carabidae: Trechini) in 
the southern Appalachians. Coleopt. Bull. 16:65-92. 
