Levels and patterns of genetic diversity in wild Chrysichthys nigrodigitatus in the Lagos Lagoon complex

Mitochondrial DNA control region sequences were used to investigate the genetic diversity of populations of Chrysichthys nigrodigitatus and Chrysichthys walkeri in the Lagos Lagoon complex. A total of 34 haplotypes were detected. The genetic diversity among C. nigrodigitatus as determined by haplotype and nucleotide diversities were 0.879 ± 0.033 and 0.0131 ± 0.003, respectively and the values were 0.93 ± 0.04 and 0.010 ± 0.0020 for a population of C. walkeri . The largest genetic distance was 7.01% between C. walkeri from Lagos Lagoon (WAK) and control region sequences of Chrysichthys nigrodigitatus samples obtained from different parts of the lagoon complex in 2008 (PRE). Within population differences accounted for 80.41% of total genetic variance in C. nigrodigitatus . There was no evidence of decreased genetic diversity in the populations. The mismatch distribution and neutrality test suggest that the effective size of C. nigrodigitatus population has been large and stable for a long period. Key words : Chrysichthys nigrodigitatus , Chrysichthys walkeri , Lagos Lagoon complex, mtDNA control region.