Differential phoretic host use among sympatric Caenorhabditis nematodes and an association with invasive nitidulid beetles in southwestern Germany

Abstract

Little is known about the natural history of many Caenorhabditis nematodes, despite their relationship to the model species C. elegans. While these nematodes rely on invertebrate vectors to disperse to new habitats (phoresy), vector use for most species has not been characterized. We surveyed the invertebrate community of a habitat containing three sympatric Caenorhabditis in southwestern Germany, determining differential and specific vector use for each of these co-occurring species. We documented a specific association between C. apta n. sp. and two species of invasive nitidulid beetles, and a particularly strong association of the nematode with the beetle Stelidota geminata, where we recovered more nematodes per individual beetle and a higher proportion of beetles carrying nematodes compared to the co-occurring Epuraea ocularis. Our results provide evidence for group dispersal using beetles in C. apta, supporting previous observations of collective dispersal behavior in this species, and establish a starting point for further dissecting the evolutionary and mechanistic causes and consequences of interactions between Caenorhabditis nematodes and their vector species in ecologically relevant conditions.