Biodiversity of Freshwaters - Freshwater Ecology: Concepts and Environmental Applications - page 187

Lake Tanganyika is millions of years old and is renowned for its large
number of endemic fishes, dominated by the perch-like tropical cichlid fishes.
Greenwood (1974) reported that the family Cichlidae is represented by 126
species, all of which are endemic. An additional 67 species of fishes from
other families are found in Tanganyika, 47 of which are endemic. Coulter
(1991a) reported 287 species and subspecies of fish, 219 of which are found
only in Tanganyika. Lakes Victoria and Malawi have more species of Cichli-
dae but not more endemic species in other families, and they have fewer en-
demic genera. The variety of adaptations that have evolved in these fish is as-
tounding (Meyer, 1993). Various species of fish in this one family live by
eating zooplankton, phytoplankton, gastropods, benthic algae, macrophytes,
detritus, or fish. Among the piscivores, some eat the scales of other fish and
have evolved to look like their prey so they are not detected as predators
(Fryer and Iles, 1972). The diversity of body form in just the one family,
Cichlidae (Fig. 10.5), can exceed that seen in all families found in some
temperate habitats.
Behavioral diversity in the Cichlidae is also high (Hori et al., 1993).
Wide variation in coloration (Axelrod, 1973) is probably related to
sexual selection that leads to sympatric speciation (i.e., evolution of a
species within one habitat; Seehausen and van Alphen, 1999). Many ci-
chlids exhibit parental care, which ranges from guarding eggs and fry
from predators to incubating eggs and protecting fry in the oral cavity
(Keenleyside, 1991). Two species can brood in the same region and mu-
tually defend against predators. In another case of evolved cooperation,
mixed groups of predators can cooperate to increase success (Nakai, 1993).
FIGURE 10.5 Some of the many varieties of fish in the family Cichlidae from Lake
Tanganyika. Julidochromis, omnivorous; Petrochromis, herbivorous; Tropheus, herbivorous;
Cyphotilapia, ambush predator, gastropods; Bathybates, pisciverous; Lobochilotes, insectivo-
rous. (from Gillespie et al., 2001)