The phylogenetic relationship and cross-infection of nucleopolyhedroviruses between the invasive winter moth (Operophtera brumata) and its native congener, Bruce spanworm (O. bruceata)

Abstract

Disease can affect biological invasions by acting as either a synergist or antagonist. Disease-mediated invasions have important implications for understanding the spread of invasive insects, which cost billions of dollars in damages annually. One such non-native, destructive insect is the winter moth, Operophtera brumata L. (Lepidoptera: Geometridae), which causes defoliation and mortality of deciduous trees in its introduced range. In the northeastern United States, winter moth populations overlap with a native congener, Bruce spanworm, Operophtera bruceata Hulst. Nucleopolyhedrovirus (NPV), appears to be an important natural enemy in Bruce spanworm and there is some evidence that the NPV infection found in winter moth in the northeastern U.S. may originate from Bruce spanworm. By sequencing two viral genes (the polyhedrin and p74 genes) from field-collected larvae of both species, we found that the winter moth virus (OpbuNPV) is distinct from the virus from Bruce spanworm (OpbrNPV). However, the two viruses do constitute a clade within the Alphabaculovirus Group 2 NPVs, indicating that they are more similar to each other than they are to other lepidopteran viruses, even other geometrid-derived NPVs. As far as we know, this is the first report of sequences from an NPV from Bruce spanworm. Results from cross infection trials suggest that cross infection is uncommon if it occurs at all. Our results show that these two closely related species have distinct viruses and, unlike previous suggestions, Bruce spanworm virus is not mediating the winter moth invasion.

Keywords: Disease mediated invasion; Nucleopolyhedrovirus; Operophtera bruceata; Operophtera brumata; Phylogenetic comparisons, host specificity.