44 
Carter R. Gilbert 
east to the Suwannee, whereas F. lineolatus is an Atlantic slope form 
occurring from extreme southeastern Virginia south throughout most of 
peninsular Florida and west to the Apalachicola drainage. Outside the 
area of distributional overlap, these species regularly occur both above 
and below the Cody Scarp, but within the area of overlap (i.e., the 
Suwannee to the Apalachicola) their distributions usually appear to be 
strongly influenced by this physiographic break, with most populations 
of F. lineolatus occurring above and most populations of F. escambiae 
below (Fig. 7). This correlation holds up especially well in the Ochlock- 
onee and Suwannee drainages, except in Telogia Creek (the principal 
western tributary of the Ochlockonee), from which F. lineolatus appears 
to be absent. In the Ochlockonee River proper the two forms come in 
close proximity, but have been collected together only twice (UF-FSU 
323 and 6002), from a locality just below the Lake Talquin (= Jackson 
Bluff) dam, which is situated along the scarp on the main river. In both 
cases gene interchange appears to have occurred (pers. observ.), despite 
previous information to the contrary (Rivas 1966, Swift et al. 1977). In 
the Suwannee drainage the two are more widely separated, F. escambiae 
occurring only in the lower river, upstream to the Santa Fe River, and 
F. lineolatus in the upper reaches. Neither species has yet been encoun- 
tered in the intervening 120-km stretch of the Suwannee River proper, 
above the mouth of the Santa Fe. In the Santa Fe system, F. escambiae 
ranges upstream to the point where the river emerges from under- 
ground, whereas in the sections above the Santa Fe Sink only F. lineo- 
latus occurs. The area where the Santa Fe descends underground is pre- 
cisely on the edge of the scarp. 
In the Suwannee drainage the distributions of several other species 
also appear to be limited by this physiographic feature. This is best 
demonstrated by Fundulus cingulatus , whose distribution in the Santa 
Fe and upper Suwannee parallels almost exactly that of F. lineolatus 
(Gilbert and Burgess 1980d). Other species limited to lower parts of the 
Suwannee drainage include Fundulus seminolis (also absent from the 
upper Santa Fe system), Micropterus notius , Fundulus chrysotus and 
Notropis petersoni (Gilbert 1980f,g; Shute 1980; Swift 1980a). Species 
confined to the upper sections of the Suwannee include Notropis leedsi, 
Notropis texanus and Notropis venustus (Gilbert 1980d, Swift 1980b, 
Gilbert and Burgess 1980b). Unlike the situation involving F. escambiae 
and F. lineolatus , there is, in many cases, considerable overlap in ranges 
of these “upstream” and “downstream” species. 
The distributional break between F. escambiae and F. lineolatus 
may be equally sharp in the St. Marks drainage, but as yet collections 
from upsteam have failed to yield individuals of either species. There are 
