Biodiversity loss; Conservation; Endemic; Host specificity; Coevolution; Phytomonas; Heteroptera

Most remote and oceanic islands are important, yet highly vulnerable biodiversity hotspots, which host a significant proportion of endemic species. Along with iconic endangered or extinct animals and plants, the disappearance of their co-inhabitants, including protist parasites, gets usually unnoticed from the conservation perspective. Here, we examined insects from Madagascar, Reunion, and Mauritius for the presence of trypanosomatid parasites (Kinetoplastea). Out of 660 specimens of the true bugs (Heteroptera) belonging to 87 species and 18 families, 95 individuals of 30 species were found to be infected (14% prevalence) by at least one trypanosomatid species, here referred to as typing units (TUs). Out of 141 flies (Diptera), 19 (13%) were infected. High diversity of the host species correlated with a high diversity of detected TUs belonging to 11 trypanosomatid genera, and representatives of 7 genera (Angomonas,Blastocrithidia,Herpetomonas, 'jaculum',Leptomonas,Wallacemonas, andZelonia) yielded axenic cultures. Of 39 detected TUs, more than half have not been encountered in other geographical regions and appear to be endemic. Altogether, 27 TUs, including 15 newly detected ones, were found exclusively in bugs, while flies hosted 11 TUs, out of which five were found exclusively on the studied islands. Only a single species,Leptomonas moramango, was found in both insect groups. Several new isolates have significantly extended the diversity of the plant-pathogenicPhytomonas. Geographically widespread as well as endemic TUs were detected in both widely distributed and (sub)endemic insects. The high proportion of endemic TUs suggests that the prominent role of islands in the global diversity of macroscopic organisms likely extends also to their protistan parasites and that the protection of macro-organisms in biodiversity hot spots can also protect the vast, yet mainly invisible, diversity of their parasitic companions.