Novel interspecies co-habitation of anthropogenic structures leads to host-species expansion in an ectoparasitic hemipteran vector, the swallow bug, Oeciacus vicarius

The modification of landscapes has the potential to impact the ecology and evolution of species occupying them. This, in part, may be driven by novel yet significant interactions between species that have previously experienced little to no contact. The significance of these interactions may be enhanced through the co-invasion of parasites (i.e., those that have been co-introduced and then spread to new, native hosts), yet few opportunities exist to study this process on a contemporary time frame; fewer still of the recent co-invasion of animal ectoparasites of disease vectoring significance. Here we present ecological and genetic data of the recent co-invasion of a hemipteran ectoparastite, the swallow bug, Oeciacus vicarius, a vector of Buggy Creek virus (Togaviridae, Alphavirus), an arbovirus within the western equine encephalomyelitis virus complex that circulates in colonially nesting cliff swallows (Petrochelidon pyrrhonota). Over the past half-century anthropogenic modification of landscapes has seen a transition in the primary nesting habits of the cliff swallow from its ancestral cliff faces to contemporary nest sites under bridges and culverts. Within these new environments, inter-species interactions now exist between the cliff swallow, the barn swallow, and the house sparrow, when nest sites are cohabitated; and along with this has been the spread of the swallow bug to these new, alternative hosts. The evolutionary and potentially significant ecological significance of this host-species expansion will be discussed.