| Description |
Universal species identification using specific molecular tags derived from the cytochrome c oxidase subunit 1 gene (COI) of the mitochondrial DNA, has successfully been implemented in many taxonomic groups. Correspondingly, molecular characterisation has revealed cryptic species. However, incongruence between morphological and genetic results in well-studied monogenean species was documented in members of Diplectanidae (Monogenea). In our study, we tested the link between the level of genetic and morphological differentiation for diplectanid parasites infecting latid hosts in geographically isolated areas in Lake Albert and Lake Tanganyika. Specimens from five African latid species (Lates angustifrons, L. mariae, L. microlepis, L. niloticus, L. stappersii) were examined for the presence of monogenean gill parasites from several localities. Monogeneans were characterised morphologically via morphometrics of sclerotised structures and genetically using markers with different rates of molecular evolution from nuclear ribosomal and mitochondrial DNA regions. In total, four out of five latid species were infected by monogenean parasites belonging to Diplectanum. Continuous morphological variation was documented, and the genetic distance between parasites of geographically isolated host species in the COI region did not reach the previously published threshold of 14.5%. Therefore, a single species, D. lacustre, is suggested to infect latids in both lakes. Based on the age of the eastern African Rift Lake system (9 MYA), the substitution rate in the COI region of D. lacustre was estimated to be 0.5%. Despite the persistent geographic barrier, D. lacustre has not reached the threshold of genetic differentiation in COI gene proposed for species delineation of diplectanid monogeneans. Congruence between the slow rate of molecular evolution in the mitochondrial COI region and the level of parasite morphological differentiation is suggested. Universal species identification using specific molecular tags derived from the cytochrome c oxidase subunit 1 gene (COI) of the mitochondrial DNA, has successfully been implemented in many taxonomic groups. Correspondingly, molecular characterisation has revealed cryptic species. However, incongruence between morphological and genetic results in well-studied monogenean species was documented in members of Diplectanidae (Monogenea). In our study, we tested the link between the level of genetic and morphological differentiation for diplectanid parasites infecting latid hosts in geographically isolated areas in Lake Albert and Lake Tanganyika. Specimens from five African latid species (Lates angustifrons, L. mariae, L. microlepis, L. niloticus, L. stappersii) were examined for the presence of monogenean gill parasites from several localities. Monogeneans were characterised morphologically via morphometrics of sclerotised structures and genetically using markers with different rates of molecular evolution from nuclear ribosomal and mitochondrial DNA regions. In total, four out of five latid species were infected by monogenean parasites belonging to Diplectanum. Continuous morphological variation was documented, and the genetic distance between parasites of geographically isolated host species in the COI region did not reach the previously published threshold of 14.5%. Therefore, a single species, D. lacustre, is suggested to infect latids in both lakes. Based on the age of the eastern African Rift Lake system (9 MYA), the substitution rate in the COI region of D. lacustre was estimated to be 0.5%. Despite the persistent geographic barrier, D. lacustre has not reached the threshold of genetic differentiation in COI gene proposed for species delineation of diplectanid monogeneans. Congruence between the slow rate of molecular evolution in the mitochondrial COI region and the level of parasite morphological differentiation is suggested.
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