40 
Thomas C. Barr, Jr. 
was thus implied, each “pulse” corresponding to colonizations at the 
beginning of each interglacial. Polytypic Trechus hydropicus and T. 
cumberlandus show present distribution patterns suggesting how a 
Unaka-based stock might have spread west and north (Barr 1969, 1979a). 
Study of the engelhardti complex, coupled with concurrent examina- 
tion of cave trechines west of the Allegheny plateau (Barr, in prepara- 
tion), suggests a different interpretation. 1) With the notable exception of 
the engelhardti group, species groups of Pseudanophthalmus on opposite 
sides of the Allegheny Plateau are quite distinct and mutually exclusive. 
The small genera of eastern cave trechines — Neaphaenops (see Barr 
1979b), Darlingtonea, Ameroduvalius, and Nelsonites (see Valentine 
1952) — are limited to Kentucky and part of Tennessee west of the 
Alleghenies; they have no counterpart in the Appalachian valley. 2) In 
Appalachian valley caves the majority of Pseudanophthalmus species are 
concentrated near the Allegheny front and become increasingly rare 
toward the Unaka front. 3) No edaphobitic species of Pseudanophthal- 
mus have been found in the Unaka region, despite considerable searching 
during the past 20 years. In fact, the only edaphobitic, noncavernicolous 
species of Pseudanophthalmus thus far known from eastern United 
States is P. sylvaticus (Barr 1967b), from Pocahontas County, West Vir- 
ginia, in the heart of the Allegheny Plateau. 4) The pattern of species 
distribution in caves is not what one would expect from repeated expan- 
sion and contraction of an ancestral stock from a Unaka source. Only the 
engelhardti group shows this sort of pattern — a series of closely similar 
species strung out as if on a chain of islands in an archipelago, with 
representatives on both sides of the Alleghenies. All other species groups 
in the genus differ substantially across the Allegheny Plateau. The caves 
of two karst islands — Grassy Cove and Pine Mountain — are inhabited 
by species of the jonesi and hypolithos groups, other species of which are 
found in Appalachian valley caves to the east. 
The significance of the Allegheny Plateau as an interglacial refugium 
for Pseudanophthalmus ancestors has been neglected in favor of Jean- 
nel’s Unaka refugium hypothesis. As an alternative view I offer the possi- 
bility that the source of many, perhaps most, of the species groups of 
Pseudanophthalmus was the upland forest of the Allegheny Plateau. The 
diversity within the genus and the difficulty of relating species groups on 
opposite sides of the Allegheny Plateau — only the gracilis group (east) 
and inexpectatus group (west) seem clearly related (Krekeler 1973) — 
suggest that considerable precave diversification may have taken place 
within the plateau, and that only those groups near karst areas survived 
the warm, dry, climatic regimes of four successive interglacial periods. In 
fact, the level of intrageneric diversity opens up the possibility that 
Pseudanophthalmus is much older than the Pleistocene. Jeannel (1949 
