Old hosts as treasure troves of worms, worms as tags for new hosts: the overlooked potential of helminthology in invasion biology

Abstract

Introduced alien species are major threats to biodiversity worldwide. Potential reasons include parasite co-introduction and transmission, aspects that are often understudied. Origins and identity of introduced species or strains are often unknown, let alone of their parasite fauna. Monitoring only provides partial answers for lack of baseline data. Especially in the Global South, native parasite biodiversity is often scarcely studied.

We studied introduced fishes and amphibians in Central and Southern African inland waters, and the monogenean parasites infecting them. Given their direct lifecycle, these flatworms are hypothesized to be easily co-introduced with their hosts, and to be useful “tags” for host populations.

Monogeneans were collected from hosts retrieved from biodiversity collections and through recent fieldwork. Parasites were morphologically identified to species level, and characterised genetically using nuclear and mitochondrial markers, including some mitochondrial genomes.

We demonstrate the potential of historical host collections to establish pre-translocation baselines for parasite communities, enabling distinguishing between native and co-introduced parasite species. Monogeneans can help trace origins and pathways of aquatic invasions. For Nile tilapia and African clawed frog, two notorious invaders, parasite mitochondrial markers provide higher resolution than host genetics.

We offer proof-of-concept of biodiversity infrastructure and helminths as sources of information in a One Health context. However, closer scrutiny of the parasitology of Nile tilapia, a fish of global economic and ecological importance, indicated that a One Health approach is mostly lacking. We recommend more scientific consideration to the parasites of invasive species, using a more integrative approach than currently often taken.