Moths vs. Bees: Contrasts in habitat preferences across barrens of the
northeastern USA
Abstract
Bees and moths are globally important pollinators. Xeric barrens in the
largely mesic northeastern USA support high levels of pollinator
diversity, including rare bees and moths. We investigated the response
of bee vs moth communities to abiotic and vegetation drivers in barrens
across the region. We sampled environment, vegetation, bees, and moths
for 2-4 years in 20 preserves. Employing random forest analysis, we
tested the role of 26 abiotic and vegetation predictors of bee vs moth
abundance, species richness, Shannon-Wiener Diversity Index, evenness,
and species composition. Variables related to climate, canopy cover, and
soils were the most important predictors of abundance, diversity, and
species composition for both bees and moths. Vegetation variables, such
as species richness of shrubs and hostplants, were also important for
bees. The direction of these relationships contrasted sharply between
bees and moths: bees were more abundant and species rich in more open,
sandy sites and moths the opposite. Surprisingly, bee-moth contrasts in
diversity did not hold for Shannon-Wiener Diversity. Habitat preferences
for a subset of moth xeric specialists were much more similar to bees
than to other moths, with a preference for open, sandy conditions.
Contrasts between bees and moths in habitat preferences likely stemmed
from differences in life history: bees rely on flowers for feeding and
porous substrates for nesting, whereas most moth adults rely on flowers
but many moth caterpillars use woody plants as hosts. The contrast
between bees and moths for species richness vs. Shannon-Wiener Diversity
raises important general questions about the conservation value of these
two metrics. Our results suggest that, because of differences in habitat
preferences among pollinators, barrens management for spatial and
temporal heterogeneity is likely to promote the highest abundance and
diversity of resident pollinator communities.