BULLETIN FLORIDA STATE MUSEUM


saburrae, it is very important to the understanding of the relationship
between the disjunct populations of C. bosquianus. The slight morphologi-
cal and meristic divergence of the disjunct populations (discussed pre-
viously) suggests either a relatively short period of isolation, parallel evolu-
tion, or a slow evolutionary rate. Although each of these mechanisms is
possible, I believe the simplest explanation is that the two populations have
only been isolated since the last glaciation, about 14,000 years BP (Brookes
1977).
 The two populations of Chasmodes bosquianus could have come in
contact with each other and interbred in the southern part of Florida by
dispersing southward in response to decreased water temperature. This
dispersal in response to decreased water temperature hypothesis was pro-
posed by Walters and Robins (1961) and has been used by Smith-Vaniz
(1980) to explain the lack of divergence between populations of Hypso-
blennius. As water temperature rose following the end of the last glacial
period, the C. bosquinaus populations would disperse northward until
reaching their present geographic positions.
 EXPERIMENTAL HYBRIDIZATION
 A hybridization experiment was performed using specimens of Chas-
modes saburrae and C. bosquianus longimaxilla collected in Mobile Bay.
Hybridization was observed between a male C. saburrae and a female C.
b. longimaxilla in a 76-liter saltwater aquarium supplied with empty oyster
and gastropod shells. In addition to the two specimens mentioned above,
there was also one adult male C. b. longimaxilla in the aquarium. The three
specimens were introduced into the aquarium simultaneously. Once intro-
duced into the aquarium, the male C. b. longimaxilla established a territory
in one of the empty oyster shells while the C. saburrae male chose a
gastropod shell. This is interesting since the choices correspond to the types
of shells found in their respective habitats. The female spawned indiscrim-
inately with both males, although she also chose the oyster shells for
protection. The eggs were tended by the males until hatching. The newly
hatched conspecific and hybrid larvae were active, but due to a lack of
suitable food or some other factor, they did not survive more than a few
days.
 Due to the extreme artificiality of the enclosure in which the interspe-
cific spawning occurred, I do not feel that these results can justifiably be
used to draw taxonomic conclusions regarding the validity of the two
species, but it does at least prove that natural production of hybrids is
possible. Hybridization in marine fish species is a comparatively rare
phenomenon.
 In the areas where these species are sympatric, they appear to be
allotopically distributed. This segregation was indicated in the choice of


VOL. 29, NO. 2