30 
Carter R. Gilbert 
The unusual character of the south Georgia-peninsular Florida fish 
fauna results from (a) the relatively unvarying lowland habitat of much 
of the area, particularly the lower two-thirds of peninsular Florida; (b) 
periodic inundation of much of the area during the late Cenozoic era; 
and (c) the comparative isolation of this area from the main centers of 
faunal diversity (thus presumed centers of evolution) in southeastern 
United States, particularly the Tennessee uplands and Mobile Bay 
basin. 
Speculation on the sources of origin for various faunal elements is 
especially complicated here in comparison to other areas of the 
Southeast. The geographically intermediate position of the state in rela- 
tion to the Gulf and Atlantic slopes is largely responsible, inasmuch as a 
number of species are widespread on both slopes. In the cases of Esox 
americanus and Aphredoderus sayanus, northern and peninsular Flor- 
ida populations have been shown mostly to be subspecific intergrades 
(Crossman 1966, 1980a; Lee 1980), and thus a dual origin is clearly 
involved. Given this and related problems, only 50 of the 72 species 
under consideration could be evaluated with reasonable certainty, with 
the following results: (a) Gulf slope — 17, (b) Atlantic slope — 16, (c) 
combined Gulf and Atlantic slopes — 2, (d) peninsular Florida — 9, (e) 
southern Georgia and northern Florida — 4, and (f) marine — 2. 
It is often assumed that peninsular Florida, because of its relatively 
uniform habitat and obscure drainage divides, has an essentially homo- 
geneously distributed fish fauna, but this is far from the truth. Analysis 
of the fauna reveals distinctive distribution patterns that, in many cases, 
reflect pathways of dispersal. For example, the distribution of Percina 
nigrofasciata in the southern half of the peninsula is limited to the Kis- 
simmee River, which flows in a southerly direction down the center of 
the state and is the principal tributary emptying into Lake Okeechobee 
(Burgess 1980b). Esox niger and Lepisosteus osseus show similar dis- 
tributions, but differ in that both species are also in the Hillsborough 
River (on the west coast), which is the largest tributary to Tampa Bay 
(Crossman 1980b, Wiley 1980a). Notropis emiliae peninsularis occurs in 
the Kissimmee River, but is absent from the Hillsborough; it also 
occurs, on the lower west coast, in the Peace River system, which emp- 
ties into Charlotte Harbor (Gilbert and Bailey 1972, Gilbert 1980b). All 
of the above species are absent from the four geographically interme- 
diate, and ecologically similar, river systems between the Peace and 
Hillsborough rivers on the middle west coast (Myakka, Manatee, Little 
Manatee and Alafia rivers). 
Enneacanthus obesus and Elassoma okefenokee range southward 
only as far as the middle of the peninsula, with neither entering the 
Kissimmee system (Lee and Gilbert 1980b, Bohlke and Rohde 1980b). 
