Abstract:
The approximately 500 species of the cichlid fish species flock of Lake Victoria, East Africa, have evolved
in a record-setting 100 000 years and represent one of the largest adaptive radiations.
We examined the population structure of the endangered cichlid species
Xystichromis
phytophagus
from Lake Kanyaboli, a satellite lake to Lake Victoria in the Kenyan Yala
wetlands. Two sets of molecular markers were analysed — sequences of the mitochondrial
control region as well as six microsatellite loci — and revealed surprisingly high levels of genetic
variability in this species. Mitochondrial DNA sequences failed to detect population
structuring among the three sample populations. A model-based population assignment
test based on microsatellite data revealed that the three populations most probably
aggregate into a larger panmictic population. However, values of population pairwise
F
ST
indicated moderate levels of genetic differentiation for one population. Eleven distinct
mitochondrial haplotypes were found among 205 specimens of
X. phytophagus
, a relatively
high number compared to the total number of 54 haplotypes that were recovered from
hundreds of specimens of the entire cichlid species flock of Lake Victoria. Most of the
X. phytophagus
mitochondrial DNA haplotypes were absent from the main Lake Victoria,
corroborating the putative importance of satellite lakes as refugia for haplochromine
cichlids that went extinct from the main lake in the last decades and possibly during the
Late Pleistocene desiccation of Lake Victoria.
