46 
Carter R. Gilbert 
certain other species^ are strongly influenced by the Cody Scarp, which 
in turn delineates an ecological break between the Northern Highlands 
and Coastal Lowlands. These ecological differences alone do not appear 
sufficiently great to limit the distributions of either F. escambiae or F. 
lineolatus in those drainages in which only one of them is present. In 
areas containing both species, however, ecological competition presum- 
ably is involved and the upstream-downstream pattern is manifested, as 
for example in the Ochlockonee and Apalachicola river drainages. The 
same may not hold true in the Suwannee drainage, however, since the 
ranges of the two fishes are widely separated either by an impenetrable 
physical barrier on the Santa Fe River (i.e., the Santa Fe Sink) or by an 
extensive (120 km) stretch of river that for some reason appears not to 
be inhabited by either species. 
I theorize that Fundulus lineolatus was present in the Tallahassee 
Hills and Wicomico Peninsula during the “Wicomico high stand” (i.e., 
in the area above the present-day Cody Scarp). At the same time, F. 
escambiae is presumed to have occupied the Western Highlands to the 
west (Puri and Vernon 1964: Fig. 5; Burgess and Franz 1978: Fig. 1). As 
the sea retreated, F. escambiae presumably moved eastward to occupy 
many of the Coastal Lowland streams, but in those streams colonized 
was prevented from moving farther upstream because of ecological com- 
petition with the previously established F. lineolatus. The latter species, 
as well as many others, was present in those tributaries draining the 
eastern side of the Wicomico Peninsula, and thus had access to the 
remainder of the St. Johns River when it subsequently assumed its pres- 
ent form. It is also possible that this species was present, during the 
Pliocene, on the insular areas of peninsular Florida. 
SPECIES EVOLUTION IN NORTHERN FLORIDA 
AND SOUTHERN GEORGIA 
Northern Florida and southern Georgia are characterized by two 
endemic fishes, Micropterus notius and Ictalurus serracanthus. The first 
is restricted to the Suwannee and Ochlockonee rivers (Gilbert 1980g), 
whereas the latter occurs in these two drainages, as well as in the Apala- 
chicola and St. Marks rivers and in Econfina Creek to the west (Yerger 
1980). (Econfina Creek should not be confused with Econfina River, 
which is to the east, just beyond the Aucilla River). The present range of 
M. notius is mostly confined to areas below the Cody Scarp, whereas /. 
serracanthus is slightly more ubiquitous in its distribution. Although no 
other fishes share these same distribution patterns, two other species of 
wider occurrence ( Notropis harperi and Etheostoma edwini ) have dis- 
tributions that are more or less centered in the same area (Gilbert 1980c, 
Stauffer and Hocutt 1980), thus suggesting a similar distributional 
history. 
