Host range expansion by British moths onto introduced conifers

Abstract

Abstract. Over 2% of British angiosperm‐feeding moths (Lepidoptera) have been recorded feeding on conifers introduced to Britain, and may be undergoing host range expansion. We compared some of the life‐history traits and ecological characteristics of fifty such species, originally exploiting angiosperms and now recorded feeding on conifers, with those of 400 non‐shifting angiosperm‐feeding moths, to identify those factors linked with host shifting. Shifting species attack a wider range of angiosperms than non‐shifting species, their original hosts tend to be woody tress and shrubs, and they hatch from the egg earlier in the year. Comparisons with the random control samples suggest that larval feeding habit and overwintering stage are also important (species with less intimate relations with the host plant, and those overwintering as eggs are more likely to shift); these trends persisted when the taxonomic distribution of the shift species was controlled for, though were no longer significant. Moth species in habitats and on host plant families which are associated with conifer afforestation in upland Britain are more likely to shift, suggesting that ecological opportunity is an important factor in host range expansion.