Rangeland sharing by cattle and bees: moderate grazing does not impair bee communities and resource availability

Spatiotemporal variability and foraging behavior of bee visitors to a rare long-lived iteroparous forb, Silene spaldingii (Caryophyllaceae)

Silene spaldingii S Watson is a rare long-lived forb (Caryophyllaceae) found primarily in open native grasslands of the Inland Pacific Northwest and is putatively pollinated by one key bumble bee pollinator, Bombus fervidus (Fabricius). However, populations of bumble bees and their visitation patterns can vary dramatically, and some species are in decline including B. fervidus. Understanding the role of co-pollinators such as sweat bees (Halictidae) could be crucial as the plight of rare plants and pollinators intensifies. We collected data across three seasons (2015-2017) on the Bombus-S. spaldingii pollination system, focusing on three Key Conservation Areas in the Channeled Scablands of eastern Washington. Bee visitors to S. spaldingii were monitored and the pool-of-pollinators was surveyed with blue vane traps. Nine species of bees were observed foraging on the plant, while 2211 bees comprised of five families, 22 genera and 81 taxa were captured in blue vane traps, meaning only 11.1% of species in the pollinator pool visited S. spaldingii. Halictus tripartitus Cockerell, a sweat bee, was a common visitor to the plant, but this was the first record of visitation for several other species, including Lasioglossum buccale (Pérez) which has never before been recorded in the Americas. These sweat bees appear to vector S. spaldingii pollen, suggesting they are co-pollinators of the plant. Weather and patch characteristics affected visitation patterns and the pool-of-pollinators. We conclude that sweat bees are likely co-pollinators of S. spaldingii and that they could become increasingly important if B. fervidus populations continue to decline.

Insect Abundance and Diversity Respond Favorably to Vegetation Communities on Interim Reclamation Sites in a Semi-Arid Natural Gas Field

Natural resource extraction has been linked to habitat loss and declines in biodiversity. Insects, the most diverse and abundant animals on Earth, provide a wide array of critical ecosystem services, but are typically understudied in terrestrial restoration projects. Here, we examine how insects and other arthropods respond to reclamation efforts in the Pinedale Anticline natural gas field in semi-arid Wyoming, USA. Vegetation on two-year-old well pads seeded with native grass or one-year-old well pads seeded with a native annual forb, Rocky Mountain bee plant (Cleomeserrulata), was measured and compared to reference areas adjacent to the well pads with a free software program called SamplePoint. Reference areas in the Pinedale Anticline natural gas field consist primarily of decadent sagebrush stands with low floral diversity. Insect and arthropod communities were also collected and assessed for family richness and abundance on these well pads and reference areas over two years. Based on the mass flowering hypothesis, we expected higher insect abundance and diversity on well pads seeded with the Rocky Mountain bee plant compared to adjacent reference areas. Based on the plant vigor hypothesis, we expected higher insect abundance and diversity on well pads seeded with native grass than reference communities. In year one, 893 insects from 30 insect families with an additional 12 arthropods from 4 families were captured. In year two, 685 insects from 17 families were collected. Reclaimed well pads had significantly higher abundance in both years and vegetation types. In year one, we did not detect a significant difference in richness on native-grass-treated well pads vs. the reference site. We found a significant difference in richness on bee-plant-treated well pads vs. the reference in both years, as well as native-grass-treated well pads vs. the reference in year two. Implications of these findings are discussed in the manuscript.