Butterfly nectar foraging and flowering plant community data from field surveys in Victoria, British Columbia, Canada

The negative impacts of non-native species have been well documented, but
some non-natives can play a positive role in native ecosystems. One way
that non-native plants can positively interact with native butterflies is
by provisioning nectar. Relatively little is known about the role of
phenology in determining native butterfly visitation to non-native plants
for nectar, yet flowering time directly controls nectar availability.
Here, we investigate the phenological patterns of flowering by native and
non-native plants and nectar foraging by native butterflies in an oak
savanna on Vancouver Island, British Columbia, Canada. We also test
whether native butterflies select nectar sources in proportion to their
availability. We found that non-native plants were well integrated into
butterfly nectar diets (83% of foraging observations) and that visitation
to non-natives increased later in the season when native plants were no
longer flowering. We also found that butterflies selected non-native
flowers more often than expected based on their availability, suggesting
that these plants represent a potentially valuable resource. Our study
shows that non-native species have the potential to drive key species
interactions in seasonal ecosystems. Management regimes focused on
eradicating non-native species may need to re-consider their aims and
evaluate resources that non-natives provide.