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

Center for Infectious Disease Dynamics, Department of Biology, 208 Mueller Laboratory, The Pennsylvania State University, University Park, PA 16802, USA; Tern and Plover Conservation Partnership, University of Nebraska, 3310 Holdrege St, Lincoln, NE 68583, USA; Department of Preclinical Sciences, Faculty of Medical Sciences, University of the West Indies, St. Augustine, Trinidad, West Indies
Evolutionary Ecology (Impact Factor: 2.41). 01/2011; 25(2):403-416. DOI: 10.1007/s10682-010-9419-9

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.

KeywordsArbovirus–Buggy Creek virus–Cliff swallow–House sparrow–Swallow bug–Virus evolution–Virus population genetics

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