Public interest in the planting of pollinator-friendly gardens has increased in part from greater awareness of recent pollinator declines. These planted gardens are typically small, managed plots containing nectar plants as forage for adults and larval host plants for caterpillars. Gardens are promoted as positively influencing the abundance and diversity of pollinators, but the extent to which these human-created habitats support pollinator conservation remains unclear. Here we report on an experiment, in which we examined whether garden features predict their use by one guild of pollinators, butterflies, within a single growing season. We established 12 replicate plots that differed according to plant species choice (native vs. exotic plants) and weed maintenance intensity (low or high). We quantified the abundance, diversity, and species composition of butterflies in plots on a weekly basis, and monitored four focal butterfly species (monarchs, queens, black swallowtails and gulf fritillaries) for egg and caterpillar abundance.
Results/Conclusions
Results showed a positive influence of flowering plants on abundance and diversity of butterflies, but no effect of plant type (exotic vs. native plants), or weed maintenance intensity. Survival of eggs to late larval instars was similar in all plots, except for the gulf fritillary, which showed greater survival probability in exotic plots. Two out of four focal butterfly species (monarchs and queens) were more abundant in exotic gardens and showed higher oviposition on the non-native host plant, Asclepias curassavica. While high egg numbers might seem beneficial for the conservation of monarch and queen butterflies, we show that greater egg and larval densities on non-native A. curassavicaleads to greater disease risk. Overall, these results showed that butterflies were attracted to all plots examined and used them for reproduction, yet two common species, monarchs and queens, showed preference for non-native plots, with important consequences for disease.