Abstract
Butterflies and other insect pollinators are declining at an alarming rate worldwide. In the state of Massachusetts, 44 species of butterflies and moths are listed as either Endangered, Threatened, or of Special Concern, with many more species showing significant population declines. Butterfly decline poses a major threat to ecosystem services supporting human health and well-being due to the important role that butterflies play as pollinators of native plants and as larva, a primary food source of birds and other wildlife. Although the anthropogenic drivers of butterfly decline remain unknown, the loss of high-quality habitat and the decline of native plant species have been identified as significant contributing factors. Yet, we presently lack the ecological data needed to develop effective conservation and restoration strategies for imperiled species. In particular, there is a lack of data on how floral use patterns vary among lepidopteran species, resulting in a ‘one size fits all’ approach to nectar plant recommendations for foraging habit restoration efforts. Moreover, current nectar plant recommendations for butterflies often include non-native plant species, further degrading native butterfly-plant pollinations systems and the wildlife diversity that they support. My research aims to fill this critical knowledge gap by documenting butterfly-nectar plant relationships across disturbed landscapes to determine whether imperiled species have specific foraging preferences that are being overlooked by the current one-size-fits-all approach to butterfly conservation. The availability of suitable host and nectar plants is essential for the persistence of butterfly populations. While laboratory research has been conducted to confirm host plant use of several species of butterflies native to Massachusetts, minimal field research has been done to understand nectar resource preferences in native butterflies, particularly nectar preferences of imperiled species for native plants. Many pollinator planting guides have been published to bring light to the issue of pollinator decline, however there is little consistency across planting guides, and very little empirical data to support the view that recommendations are actually helping butterfly species at risk of local extinction. To quantify variation in nectar plant preferences among butterfly species, I conducted field surveys of butterfly-flower interactions at four field sites in Massachusetts across two field seasons. A total of 2,490 observations and 55 species were collected over a 2-year period. These data were used to determine whether butterflies exhibit species-specific floral preferences. My results demonstrate that distinct floral resource preferences exist for many species, both stable and declining. All 25 lepidopteran species that were found at a minimum of one site showed a significant preference or avoidance for at least one floral trait. 20 species showed a significant preference for long-tubed flowers at a minimum of one field site while three showed a significant avoidance of long-tubed flowers, and eight showed a significant preference for native flowers at a minimum of one field site while 16 showed an avoidance of native flowers at one or more field sites. Of the 13 species present at more than one field site, all species showed consistent preferences or avoidances for at least one floral trait across two or more field sites with varying floral landscapes. To assess how effective pollinator planting guides for the Northeast were in their recommendations, I ranked four planting guides created by professional conservation organizations by how well the recommended plants on each list supported a diversity of stable and declining lepidopterans and compared them to a data-driven guide that I created based off diversity indexes that were calculated with the collected field data. Though each published guide included plants with high diversity indices, each guide also included plants with very low diversity indices and failed to include plants with high diversity indices. Ultimately, the data-driven planting guide I created supports a higher average diversity of species and a higher average number of species of conservation concern than all four published guides. The results of these studies suggest that ecological differences in floral resource use exist between butterfly species, and that current conservation and habitat restoration efforts for butterfly pollination systems in Massachusetts would benefit from more data-driven recommendations that consider ecological and behavioral differences among species.