Parasitic monogenean flatworms as tags for invasive aquatic vertebrates in Africa, using mitochondrial markers and historical collections

Abstract

Reasons why introduced alien species are major risks to biodiversity include parasite co-introduction and lateral transfer to local hosts, but this parasitological impact is understudied. The origins and identities of introduced organisms are often unknown, including those of their parasite fauna. Recent species monitoring only provides partial answers for want of baseline data: especially in the Global South and in sub-Saharan Africa in particular, where native parasite biodiversity is poorly known. We studied introduced vertebrates (cichlids, sardines, frogs) in Central and Southern African inland waters, and parasitic flatworms (monogeneans) infecting them. Given their obligate one-host lifestyle, these parasites are thought to be more easily co-introduced with their hosts, and to be used as “tags” for the origin and introduction pathway of host populations. Parasites were isolated from hosts sampled from historical collections and in recent fieldwork. Monogenean parasites were morphologically identified to species level, and characterised using nuclear and mitochondrial markers. Using historical fish collections to reconstruct pre-introduction baselines for cichlid parasite communities, we distinguished between native and co-introduced parasite species, and detected parasite transmission to native cichlids. Monogeneans helped identify origins and introduction pathways of invasive sardines. For the notoriously invasive Nile tilapia and African clawed frog, these parasites provided a higher resolution than host genetics. This a proof-of-concept of biodiversity infrastructure and parasites as information sources for invasion biology. Nevertheless, a review of the state-of-the-art of parasitological research on Nile tilapia, an invasive fish of global economic and ecological importance, shows that work on its parasites mostly overlooks their indicator potential. We recommend more scientific consideration to the parasites of invasive species, using a more integrative approach than is currently often taken.