Cryptic diversity and gene introgression of Moinidae (Crustacea: Cladocera) in Nigeria

The distribution and species/lineage diversity of freshwater invertebrate zooplankton is understudied in Sub-Saharan Africa. In the present study, we explored the lineage diversity and regional distribution of Moinidae (Crustacea: Cladocera) species in Southeast Nigeria. Three species of Moinidae were identified, based on morphology, in 11 of 32 Nigerian lakes examined. Their phylogenetic relationships were investigated based on mitochondrial DNA sequences (cytochrome oxidase c subunit I gene; COI) and two nuclear internal transcribed spacer regions (ITS-1 and ITS-2). Three COI lineages were detected, corresponding to the morphological species. Two of the COI lineages are newly reported, but one COI lineage (and the haplotype found) is globally distributed, suggesting an ability of moinids to disperse over long distances. Interestingly, two individuals that were morphologically M. cf. macrocopa and had ITS alleles typical of that species had mtDNA sequences typical of M. cf. micrura. Additionally, one individual that corresponded morphologically to M. cf. macrocopa (and also had a mitochondrial sequence typical of M. cf. micrura) had one ITS-2 allele typical of that species and one typical of M. cf. micrura. This discordance between mtDNA and nuclear phylogenies suggests gene introgression and/or hybridization between different species within the genus. Our data shows the lineage distribution/diversity and the presence of gene introgression/interspecific hybridization among moinid species from a tropical region.