444
JAMES E. DEACON AND W. L MINCKLEY
limited in its eastern distribution by the less saline waters (or by the more
saturated fauna of more well-watered zones). It often comprises the only
fish in seasonally hot, silty, far-western Kansas rivers (Metcalf, 1966;
Cross, 1967). Only a few have been taken after flooding in the eastern
side, but its proclivity for severe environments is nicely demonstrated by
the most eastern, reproducing population that occurs in a salt spring of Missouri (Miller, 1955).
Salinities may also strongly limit the distribution of species. Rivers flowing parallel and in close approximation, then entering the sea, may have
quite different components in their obligate, freshwater fish fauna. Springs
and streams entering closed-basin, saline lakes, may be even more isolated.
Great Salt Lake, for example, has freshwater fishes in tributary streams
and on their deltas (Sigler and Miller, 1963). Yet the open waters support
no aquatic vertebrate life. In the Anatolian basin of central Turkey, Kosswig (1961) and his associates have studied populations of cyprinodonts
(Aphanius, Anatolichthys, and Kosswigichthys). These have undergone
complex differentiation, then anastomosis through hybridization for thousands of years, alternating isolation by saline lake waters with periods of
intermingling when lake conditions permitted (Kosswig, 1956, 1961, 1963;
Villwock, 1958, 1966). The same type of situation may have prevailed
in some fishes of the Cuatro Ciénegas basin, Mexico, before canalization
destroyed most of the large, barrial lakes (Minckley, 1969b). LaBounty
and Deacon (1971) have drawn parallels with the apparently more
desiccated aquatic habitats in Death Valley.
Temperature may strongly influence the northern limits of ranges for
warm-adapted fishes such as the cyprinodontoids, cichlids, and characids.
In some instances, the northern limit of a fish's range may be extended by
selection of cold-hardy stocks, as in the case of mosquitofish (Krumholz,
1944, 1948), or through man-made structures or conditions that allow
them to overwinter. Damming of streams produces amelioration of winter
temperatures in some instances. This may have allowed the Mexican
tetra to establish in Oklahoma (Moore, 1968), and the threadfin shad to
move up the Ohio River (Minckley and Krumholz, 1960).
Hot waters from steam plants now allow some warm-water fishes to live
at northern latitudes (Dryer and Benson, 1957), and introductions of
tropical fishes into warm springs of cold climates have often succeeded
(McAllister, 1969; Lachner et al., 1970). The reciprocal also is true. Witness the relict populations of trout far south of the major regions of cool
or temperate climate, on high mountains of arid regions, such as Arizona,
Baja California, Mexico, and the northwestern part of the Mexican Plateau
(Miller, 1950a, 1971; Needham and Gard, 1959, 1964), as well as the
JAMES E. DEACON AND W. L MINCKLEY
limited in its eastern distribution by the less saline waters (or by the more
saturated fauna of more well-watered zones). It often comprises the only
fish in seasonally hot, silty, far-western Kansas rivers (Metcalf, 1966;
Cross, 1967). Only a few have been taken after flooding in the eastern
side, but its proclivity for severe environments is nicely demonstrated by
the most eastern, reproducing population that occurs in a salt spring of Missouri (Miller, 1955).
Salinities may also strongly limit the distribution of species. Rivers flowing parallel and in close approximation, then entering the sea, may have
quite different components in their obligate, freshwater fish fauna. Springs
and streams entering closed-basin, saline lakes, may be even more isolated.
Great Salt Lake, for example, has freshwater fishes in tributary streams
and on their deltas (Sigler and Miller, 1963). Yet the open waters support
no aquatic vertebrate life. In the Anatolian basin of central Turkey, Kosswig (1961) and his associates have studied populations of cyprinodonts
(Aphanius, Anatolichthys, and Kosswigichthys). These have undergone
complex differentiation, then anastomosis through hybridization for thousands of years, alternating isolation by saline lake waters with periods of
intermingling when lake conditions permitted (Kosswig, 1956, 1961, 1963;
Villwock, 1958, 1966). The same type of situation may have prevailed
in some fishes of the Cuatro Ciénegas basin, Mexico, before canalization
destroyed most of the large, barrial lakes (Minckley, 1969b). LaBounty
and Deacon (1971) have drawn parallels with the apparently more
desiccated aquatic habitats in Death Valley.
Temperature may strongly influence the northern limits of ranges for
warm-adapted fishes such as the cyprinodontoids, cichlids, and characids.
In some instances, the northern limit of a fish's range may be extended by
selection of cold-hardy stocks, as in the case of mosquitofish (Krumholz,
1944, 1948), or through man-made structures or conditions that allow
them to overwinter. Damming of streams produces amelioration of winter
temperatures in some instances. This may have allowed the Mexican
tetra to establish in Oklahoma (Moore, 1968), and the threadfin shad to
move up the Ohio River (Minckley and Krumholz, 1960).
Hot waters from steam plants now allow some warm-water fishes to live
at northern latitudes (Dryer and Benson, 1957), and introductions of
tropical fishes into warm springs of cold climates have often succeeded
(McAllister, 1969; Lachner et al., 1970). The reciprocal also is true. Witness the relict populations of trout far south of the major regions of cool
or temperate climate, on high mountains of arid regions, such as Arizona,
Baja California, Mexico, and the northwestern part of the Mexican Plateau
(Miller, 1950a, 1971; Needham and Gard, 1959, 1964), as well as the