Isolation by distance explains genetic structure of Buggy Creek virus, a bird-associated arbovirus

Abstract

Many of the arthropod-borne viruses (arboviruses) show extensive genetic variability and are widely distributed over large geographic areas. Understanding how virus genetic structure varies in space may yield insight into how these pathogens are adapted to and dispersed by different hosts or vectors, the relative importance of mutation, drift, or selection in generating genetic variability, and where and when epidemics or epizootics are most likely to occur. However, because most arboviruses tend to be sampled opportunistically and often cannot be isolated in large numbers at a given locale, surprisingly little is known about their spatial genetic structure on the local scale at which host/vector/virus interactions typically occur. Here, we examine fine-scale spatial structure of two sympatric lineages of Buggy Creek virus (BCRV, Togaviridae), an alphavirus transmitted by the ectoparasitic swallow bug (Oeciacus vicarius) to colonially nesting cliff swallows (Petrochelidon pyrrhonota) and invasive house sparrows (Passer domesticus) in North America. Data from 377 BCRV isolates at cliff swallow colony sites in western Nebraska showed that both virus lineages were geographically structured. Most haplotypes were detected at a single colony or were shared among nearby colonies, and pair-wise genetic distance increased significantly with geographic distance between colony sites. Genetic structure of both lineages is consistent with isolation by distance. Sites with the most genetically distinct BCRV isolates were occupied by large numbers of house sparrows, suggesting that concentrations of invasive sparrows may represent foci for evolutionary change in BCRV. Our results show that bird-associated arboviruses can show genetic substructure over short geographic distances.

Revised time scales of RNA virus evolution based on spatial information

“…A pattern of IBD at short spatial distances that decays over larger distances is thus indicative of such factors impacting on genetic divergence estimates. IBD has been detected in many organisms, including humans [19,20], with only relatively few formal reports from viruses [21][22][23][24][25]. However, many studies report the spatial clustering of nucleotide sequences in phylogenetic trees [26][27][28][29][30] which might indicate an IBD pattern.…”

Predation by ants controls swallow bug (Hemiptera: Cimicidae:Oeciacus vicarius) infestations

“…The swallow bug (Hemiptera: Cimicidae: Oeciacus vicarius ) is a vector of Buggy Creek virus (BCRV; Togaviridae, Alphavirus ), an arbovirus within the western equine encephalomyelitis virus complex that circulates in colonially nesting cliff swallows ( Petrochelidon pyrrhonota ) and introduced house sparrows ( Passer domesticus ) occupying swallow nests (Hopla , O'Brien et al , Padhi et al ). Swallow bugs increase in larger cliff swallow colonies (Brown and Brown , ), and this leads to higher BCRV prevalence at sites with more cliff swallows and/or house sparrows (Brown et al , Moore et al , O'Brien and Brown ).…”