Dale F. Schweitzer

Shrubland Lepidoptera of southern New England and southeastern New York: ecology, conservation, and management

Sandplain and ridgetop pitch pine (Pinus rigida)–scrub oak (Quercus ilicifolia) barrens and other shrub-dominated natural communities (e.g., heathlands and maritime shrublands) are important habitats for rare Lepidoptera (moths and butterflies) in southern New England and southeastern New York. Fifty-six species of conservation concern representing 11 families of Lepidoptera are recognized as dependent on shrubland habitats in this region, including 23% of Connecticut’s state-listed Lepidoptera and 41% of state-listed moths and butterflies in Massachusetts. Sixteen (29%) of these 56 species utilize scrub oak as a larval host and eight species (14%) use lowbush blueberries (Vaccinium angustifolium and V. pallidum). In addition to Lepidoptera, a wide diversity of other invertebrates is dependent on pine barrens and other shrublands. The importance of these habitats results from unique edaphic conditions and temperature regimes, as well as the structure, species composition, and phenology of the plant community. Pine barrens and other shrublands in the northeastern United States are threatened by destruction and fragmentation, as well as fire exclusion and other alterations of natural disturbance regimes. Active management, including the application of prescribed fire, mechanical cutting, or a combination of the two, is critical to the maintenance of habitat structure and species composition in barrens and other shrublands within human-dominated landscapes of the northeastern United States.

Are pollinating hawk moths declining in the Northeastern United States? An analysis of collection records

Increasing attention to pollinators and their role in providing ecosystem services has revealed a paucity of studies on long-term population trends of most insect pollinators in many parts of the world. Because targeted monitoring programs are resource intensive and unlikely to be performed on most insect pollinators, we took advantage of existing collection records to examine long-term trends in northeastern United States populations of 26 species of hawk moths (family Sphingidae) that are presumed to be pollinators. We compiled over 6,600 records from nine museum and 14 private collections that spanned a 112-year period, and used logistic generalized linear mixed models (GLMMs) to examine long-term population trends. We controlled for uneven sampling effort by adding a covariate for list length, the number of species recorded during each sampling event. We found that of the 22 species for which there was sufficient data to assess population trends, eight species declined and four species increased in detection probability (the probability of a species being recorded during each year while accounting for effort, climate, and spatial effects in the GLMMs). Of the four species with too few records to statistically assess, two have disappeared from parts of their ranges. None of the four species with diurnal adults showed a trend in detection probability. Two species that are pests of solanaceous crops declined, consistent with a seven-fold drop in the area planted in tobacco and tomato crops. We found some evidence linking susceptibility to parasitoidism by the introduced fly Compsilura concinnata (Tachinidae) to declines. Moths with larvae that feed on vines and trees, where available evidence indicates that the fly is most likely to attack, had a greater propensity to decline than species that use herbs and shrubs as larval host plants. Species that develop in the spring, before Compsilura populations have increased, did not decline. However, restricting the analysis to hawk moth records from areas outside of a “refuge” area where Compsilura does not occur did not significantly increase the intensity of the declines as would be predicted if Compsilura was the primary cause of declines. Forests have recovered over the study period across most of the northeastern U.S., but this does not appear to have been a major factor because host plants of several of the declining species have increased in abundance with forest expansion and maturation. Climate variables used in the GLMMs were not consistently related to moth detection probability. Hawk moth declines may have ecological effects on both the plants pollinated by these species and vertebrate predators of the moths.