Reproductive biology and impacts of energy development on Physaria congesta and Physaria obcordata (Brassicaceae), two rare and threatened plants in the Piceance Basin, Colorado

The Piceance Basin in western Colorado has undergone a drastic increase in oil and gas development over the last two decades. This increase has escalated concerns about the effects of development on the Basin's flora and fauna, especially the rare plant community. Potential impacts from oil and gas development on rare plants may be found through decrease in plant habitat or by a decrease in plant reproductive success through changes to important pollinator communities. Here, we observed the pollinator community on two rare mustard plants, Physaria congesta and Physaria obcordata (Brassicaceae), both listed as threatened by the US Fish and Wildlife Service (Federal Register 55 FR 4152). We studied a series of questions concerning the pollinator community important to each Physaria species. The experiments were conducted in the spring of 2010 and 2011 during the blooming season of each rare Physaria. We investigated the effect of oil and gas development on the pollinator community by evaluating abundance, diversity, behavior, and foraging rates along a distance gradient from roadsides. This study also examines plant fecundity to determine the extent of pollinator efficiency across the same distance gradient from roadsides. Additionally, we examine nesting success of pollinators within plant populations, as well as around natural gas wellpads. Further, we conduct a breeding system and cross pollination study on P. congesta to determine the importance of pollination services for reproduction. To determine overall pollinator community changes around other development types we sampled pollinators around wellpads. Our data supports the null hypothesis, suggesting that at this time oil and gas development may have little to no impact on the pollinator community abundance. The analysis conducted may not have been able to detect changes in the community, due to a small sample size of pollinators collected.;Bee pollinators may forage on a few or many floral resources. Here, we account for the ancillary foraging resources of P. congesta and P. obcordata pollinators by identifying pollen removed from bees collected on rare Physaria. This specific community of plants may require conservation in addition to the rare plants, to assist in maintaining the pollinator community.