Reproductive output of the rare plant Arctomecon californica does not appear to be pollination limited

Authors: Graham, Kelsey; DEFALCO, LESLEY - Us Geological Survey (USGS); Griswold, Terry

Submitted to: Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2025
Publication Date: 5/27/2025
Citation: Graham, K.K., Defalco, L., Griswold, T.L. 2025. Reproductive output of the rare plant Arctomecon californica does not appear to be pollination limited. Plant Ecology. https://doi.org/10.1007/s11258-025-01532-y.
DOI: https://doi.org/10.1007/s11258-025-01532-y

Interpretive Summary: The Las Vegas bearpoppy (Arctomecon californica) is a rare plant native to the northeastern Mojave Desert. It depends on bee visitors for successful reproduction. One rare bee, the Mojave poppy bee (Perdita meconis) exclusively visits poppies such as the Las Vegas bearpoppy for pollen. But local populations of this bee fluctuate greatly year to year, and it has declined drastically in parts of its range. We therefore investigated if abundance of the Mojave poppy bee corresponds to successful reproduction of the Las Vegas bearpoppy. We documented the visiting bee community to the Las Vegas bearpoppy across two years, and the corresponding reproductive success of this plant. A diverse community of bees visits the Las Vegas bearpoppy and reproduction was always very high for this plant, even when the Mojave poppy bee was absent. We therefore did not find evidence that the Las Vegas bearpoppy is dependent on the Mojave poppy bee for reproduction.

Technical Abstract: Arctomecon californica, the Las Vegas bearpoppy, is a rare plant native to the northeastern Mojave Desert. It is pollinator dependent for reproduction as it is self-incompatible. A specialist bee, Perdita meconis, specializes on Arctomecon and Argemone for pollen, but local populations of this bee fluctuate greatly year to year. We therefore investigated if A. californica has evidence of being pollination limited in a year with low P. meconis presence (2022) compared to a year where this specialist bee is more abundant (2023). We documented the visiting bee community across both years, and compared rates of A. californica seed fertilization and development across populations and between the two years. We collected and identified bees from 18 genera visiting A. californica flowers over the two years, with significant differences in the bee communities between years. There were significantly fewer overall bee visits to A. californica flowers in 2022 compared to 2023, but we found no evidence of pollination limitation in either year, with overall high rates of fertilization in both. We therefore did not find evidence that A. californica is dependent on P. meconis for reproduction.