Data from: Same school, different conduct: rates of multiple paternity vary within a mixed-species breeding school of semi-pelagic cichlid fish (Cyprichromis spp.)

Mating system variability is known to exist between and within species,
often due to environmental influences. An open question is whether, vice
versa, similar environmental conditions entail congruent mating behavior,
for example in terms of multiple paternity, in species or populations
sharing largely comparable breeding modes. This study employed
microsatellite markers to investigate the incidence of multiple paternity
in Cyprichromis coloratus and Cyprichromis leptosoma, two sympatric,
closely related, mouthbrooding Lake Tanganyika cichlids with similar
ecological and behavioral characteristics including the formation of
open-water schools. Mouthbrooding females of both species were collected
from the same mixed-species breeding school at the same time, minimizing
environmental variation during courtship and mating. In C. coloratus, four
of 12 broods had more than one sire, with a mean of 1.33 reconstructed
sires per brood. C. leptosoma exhibited multiple paternity in 18 of 22
broods, with a mean of 2.59 or 2.86 reconstructed sires per brood
according to the programs gerud and colony, respectively. In addition, two
broods were found to contain offspring transplanted from another brood.
There was no significant difference in brood size between species, but
mean sire number did differ significantly. Hence, substantial similarity
in reproductive behavior along with shared environmental conditions during
courtship and spawning did not lead to equal rates of polyandry or
sneaking in the two species.