Zoogeography of the Freshwater Fish Fauna 
of Southern Georgia and Peninsular Florida 
Carter R. Gilbert 
Florida State Museum, 
University of Florida, Gainesville, Florida 3261 1 
ABSTRACT . — The freshwater fish fauna of southern Georgia and 
peninsular Florida is impoverished in comparison with those of other 
areas of southeastern United States, but at the same time displays a 
relatively high percentage of endemism at species, subspecies, or racial 
levels. Historical factors relating to this are reviewed, from which it is 
concluded that peninsular Florida had its origin in the middle Oligo- 
cene epoch (about 30 million years before present), and that subse- 
quent pre-Pleistocene fluctuations in sea level resulted in complete 
insularization of the peninsula on at least two separate occasions. This 
and various related zoogeographic phenomena are discussed. 
Peninsular Florida is an important area of biological endemism 
(Neill 1957). It is generally accepted that this endemism has, in most 
cases, resulted from physical separation of the peninsula from the rest of 
southeastern United States by a saltwater barrier located in the northern 
part (“neck”) of the peninsula. Until recently, this insularization was 
believed to have been strictly a Pleistocene event, resulting from fluctua- 
tions in sea level brought about by cycles of glacial freezing and melting. 
This explanation was unsatisfactory for a number of reasons, but par- 
ticularly from the standpoint that the duration of periods of isolation 
would have been insufficient to have permitted evolution to proceed to 
its present state. In this paper I will discuss recent findings pertaining to 
pre-Pleistocene fluctuations in sea level that provide a more logical 
explanation for the above. Related problems considered include (a) 
composition, relationships and origins of the fish fauna; (b) factors con- 
tributing to faunal distinctiveness of the area, including discussion of 
the origin and biogeographic effects of Okefenokee Swamp; (c) origin of 
the St. Johns River drainage and its fauna; (d) influence of the early 
Pliocene “Cody Scarp” on the distributions of certain species; and (g) 
species evolution in southern Georgia and northern Florida, including 
the enigmatic absence of amblyopsid fishes or other cave fishes from the 
area. 
The acronym UF-FSU appearing in this paper refers to specimen 
lots originally housed in the Florida State University ichthyological col- 
lection, Tallahassee. This collection was subsequently combined in its 
entirety with that in the Florida State Museum, University of Florida, 
Gainesville. 
Brimleyana No. 13:25-54, July 1987 
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