Reproduction and pollination of the endangered dwarf bear-poppy Arctomecon humilis (Papaveraceae) across a quarter century: unraveling of a pollination web?

Authors

Vincent J. Tepedino, Utah State University, Logan, UTFollow
John Mull, Weber State University, Ogden, UTFollow
Terry L. Griswold, USDA–ARS, Logan, UTFollow
Gerald Bryant, Dixie State University, St George, UTFollow

Abstract

Arctomecon humilis, a rare gypsophile of the extreme northeastern Mojave Desert, is restricted to a few isolated populations (occurrences) in Washington Co, Utah (USA). At several points in the past quarter century, we have studied the breeding system and reproductive success of this endangered species, recorded its pollinators and tested the feasibility of human-assisted gene flow by conducting reciprocal crosses between two isolated occurrences approximately 4 km apart. We found A. humilis to possess a mixed breeding system in the occurrence studied (Beehive Dome in 1988); some plants exhibited self-compatibility but fruit/flowers and seeds/fruit were significantly lower in pollinator-effected self-pollinations than in cross-pollinations. Few fruits and seeds were produced in the absence of pollinators. The results of cross-pollination treatments did not differ from unassisted open-pollinations (controls), suggesting that pollinators were not limiting reproductive success. Several recent results (2012) suggest that some occurrences may be more at risk than others. Although all seven occurrences surveyed produced ≥ 70% fruits/flower, they differed significantly in fruit set and in average seed number/fruit and seed weight. Possible reasons for these differences, i.e., inbreeding, genetic load, insufficient mating types, pollinator scarcity, etc., all potentially important for conservation management, should be investigated. The pollinator community appears to have changed dramatically over the past two decades, from one composed of specialist and generalist bees to one where pollination is presently being accomplished by generalist foragers. The health of one of these generalists, Apis mellifera, the honey bee, is a current global concern and its future presence as a pollinator of A. humilis is unclear. Our reciprocal crosses between the White Dome and Webb Hill occurrences were mostly successful and provide support for our suggestion that gene flow in the form of human-accomplished inter-occurrence crosses be undertaken every five years to increase the genetic variability of occurrences. We end by making several other recommendations for research that would improve the ability of land managers to conserve this species.

Recommended Citation

Tepedino, Vincent J.; Mull, John; Griswold, Terry L.; and Bryant, Gerald (2014) "Reproduction and pollination of the endangered dwarf bear-poppy Arctomecon humilis (Papaveraceae) across a quarter century: unraveling of a pollination web?," Western North American Naturalist: Vol. 74: No. 3, Article 5.
Available at: https://scholarsarchive.byu.edu/wnan/vol74/iss3/5