Providing context for advancements in Arctomecon californica conservation: a comprehensive literature review with case studies

Arctomecon californica (Las Vegas bearpoppy, Papaveraceae) is a rare perennial forb endemic to southern Nevada and northwestern Arizona. This species is found primarily on gypsum and limestone soils in the southeastern Mojave Desert and is threatened by urban sprawl from Las Vegas, pollinator loss, resource extraction, energy development, and off-highway vehicle recreation. While A. californica has been the focus of several studies and conservation efforts for decades, much of the research on this plant has remained unpublished and inaccessible. To ensure all stakeholders have access to all the existing knowledge of this species, we have reviewed and summarized 70 works including gray literature and sources not previously digitized. We hope to support further research and conservation by providing a comprehensive and accessible summary of A. californica knowledge, including our efforts to improve conservation and restoration methods. We found that many aspects of A. californica biology remain unknown, including habitat preferences. Through a root excavation, we found that A. californica can root much deeper than previously recorded, to soil depths of at least 123 cm. We also found that root diameter varied greatly across depths. We conducted a salvage effort which resulted in plants surviving at least 22 months after transplant, with many of them producing seed. Though direct seeding continues to be challenging, we succeeded in growing plants to seedling stage ex situ for the first time. We found that despite the longevity of interest and concern for this species, there are still significant knowledge gaps that restrict the ability of agencies to manage existing populations, understand threats, or conduct successful habitat restoration. New research has led to the advancement of knowledge in several key areas but also effectively highlights the questions that still need to be answered about A. californica in order to support its conservation.