Intraspecific diversification and mitonuclear discordance in native versus introduced areas: co-introduction ofDolicirroplectanum lacustre, a monogenean gill parasite of the invasive Nile perchLates niloticus

The Nile perch ( Lates niloticus ) is a notorious invasive species. The introductions of Nile perch into several lakes and rivers in the Lake Victoria region led to the impoverishment of the trophic food webs, particularly well documented in Lake Victoria. Along with the introductions of the Nile perch, its parasites were co-introduced. Dolicirroplectanum lacustre (Monogenea, Diplectanidae) is a gill parasite of latid fishes ( Lates spp.) inhabiting several major African freshwater systems. We examined the intra-specific diversification of D. lacustre from L. niloticus in Lake Albert (native range) and Lake Victoria (introduced range) by assessing morphological and genetic differentiation, and microhabitat preference. We expected reduced morphological and genetic diversity for D. lacustre in Lake Victoria compared to Lake Albert, as a result of the historical introductions. Dolicirroplectanum lacustre displays high morphological variability within and between African freshwaters. Mitonuclear discordance within the morphotypes of D. lacustre indicates an incomplete reproductive barrier between the morphotypes. The diversification in the mitochondrial gene portion is directly linked with the morphotypes, while the nuclear gene portions indicate conspecificity. Based on our results, we reported reduced genetic and morphological diversity, potentially being a result of a founder effect in Lake Victoria.