Abstract
Interest in bees has grown dramatically in recent years in light of several studies that have reported widespread declines in bees and other pollinators. Investigating declines in wild bees can be difficult, however, due to the lack of faunal surveys that provide baseline data of bee richness and diversity. Protected lands such as national monuments and national parks can provide unique opportunities to learn about and monitor bee populations dynamics in a natural setting because the opportunity for large-scale changes to the landscape are reduced compared to unprotected lands. Here we report on a 4-year study of bees in Grand Staircase-Escalante National Monument (GSENM), found in southern Utah, USA. Using opportunistic collecting and a series of standardized plots, we collected bees throughout the six-month flowering season for four consecutive years. In total, 660 bee species are now known from the area, across 55 genera, and including 49 new species. Two genera not previously known to occur in the state of Utah were discovered, as well as 16 new species records for the state. Bees include ground-nesters, cavity- and twig-nesters, cleptoparasites, narrow specialists, generalists, solitary, and social species. The bee fauna reached peak diversity each spring, but also experienced a second peak in diversity in late summer, following monsoonal rains. The majority of GSENM’s bees are highly localized, occurring in only a few locations throughout the monument, and often in low abundance, but consistently across the four years. Only a few species are widespread and super-abundant. Certain flowering plants appear to be inordinately attractive to the bees in GSENM, including several invasive species. GSENM protects one of the richest bee faunas in the west; the large elevational gradient, incredible number of flowering plants, and the mosaic of habitats are all likely contributors to this rich assemblage of bees.
Highlights
Several recent analyses have concluded that certain species of wild bees may be in decline (e.g., Bartomeus et al, 2013; Goulson et al, 2015; Potts et al, 2010)
Grand Staircase-Escalante National Monument (GSENM) encompasses a rich bee fauna (Fig. 2); 660 species in 55 genera (Table S1) were recorded from GSENM, including all six bee families extant in North America. This represents approximately 55% of the described bee species known from the state of Utah, and about 64% of bee species found on the Colorado Plateau
Despite the relatively small geographic area, the number of bee species found in GSENM is comparable to the number of bee species known from the entire eastern US
Summary
Several recent analyses have concluded that certain species of wild bees may be in decline (e.g., Bartomeus et al, 2013; Goulson et al, 2015; Potts et al, 2010). Few standardized bee collections were made prior to the last two decades (Bartomeus et al, 2013; Biesmeijer et al, 2006), so there are few baseline data points against which to measure present-day bee population sizes Those few standardized collections that are older than twenty years are often in areas where the landscape has been significantly altered, so that collection events today may be sampling a much different habitat, from a bee’s perspective (Biesmeijer et al, 2006)
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