Phylogenetic relationships among monogenean gill parasites (Dactylogyridea, Ancyrocephalidae) infesting tilapiine hosts (Cichlidae): systematic and evolutionary implications.

We studied the systematics of 14 species of monogenean (Ancyrocephalidae) gill parasites from West African tilapiine hosts (Cichlidae) using both morphological and genetic data. With these tools, we were able to: (i) confirm the validity of the previously described morphological parasite species and of the genus Scutogyrus; (ii) propose that some stenoxenous species (i.e., parasite species with more than one host) may be composed of sister species (e.g., Cichlidogyrus tilapiae); (iii) state that the use of the morphology of the haptoral sclerites is more suitable to infer phylogenetic relationships than the morphology of the genitalia (which seems to be more useful to resolve species-level identifications, presumably because of its faster rate of change). These results imply that: (i) the specificity of these monogenean parasites is greater than initially supposed (what were thought to be stenoxenous species may be assemblages of oïoxenous sister species); (ii) related species groups (i.e., "tilapiae," "halli," and "tiberianus") have to be, as genus Scutogyrus, validated within the 54 ancyrocephalid species described from 18 species of tilapiine hosts in West Africa, (iii) the group "tilapiae," due to its morphology and host range, have to be considered as being the most primitive; (iv) the occurrence of lateral transfers and parallel speciation processes are necessary to describe the repartition of the newly described parasite groups on the three host genera studied (Tilapia, Oreochromis, and Sarotherodon).