Physaria kaibabensis (Brassicaceae) is endemic to the Kaibab Plateau of northern Arizona. The species is found in open areas where Kaibab limestone is exposed. Plants are perennials with a basal rosette of leaves where flower stalks arise in early summer. Due to a limited range, its status is being evaluated for federal listing. Our main objectives were: 1) to describe and compare different sites where plants occur, 2) to assess reproductive potential of plants for seed production, and 3) to evaluate germination potential. Using historic records and site visits, six sites were chosen in 2015. In early June, transects and quadrats were used to determine plant cover, bare ground and litter. Also, the presence/absence of damage from ungulates (probably deer) or rodents (probably ground squirrels) was recorded. Sites ranged from 26-72% plant cover, 20-70% bare ground, and 4-42% litter. Plant densities were negatively correlated with litter cover (r= -0.821, n=6, p=0.045). Ungulate damage and rodent damage were observed in 0-88% and 0-20% of quadrats, respectively. Ungulate damage was positively correlated with percentage of vegetative plants (r= +0.925, n=6, p=0.008). Flower stalks were counted on one plant per quadrat, and the tallest stalk was collected to measure reproductive traits. Number of flower stalks ranged from 2.4-4.4/plant at different sites. Buds, flowers, fruits and pedicels were counted to calculate seed production. Estimates were 3-70 seeds/plant at different sites. Fruits were assessed for herbivory damage with 0-33% having holes, and 0-3% having galls at different sites. Fruits were collected in late June and mid-July to obtain seeds for germination trials. Seeds were placed on moistened filter paper in petri dishes (3 replications of 50 seeds each) in a chamber at 25oC with a 16-hour photoperiod following treatments used to break dormancy. Germination ranged from 32-41% with no significant differences in control (no seed treatment), moist-stratified at 4oC for 10.5 weeks, or 24-hr presoak in 0.5 mg/ml GA. Germination trials also were performed to compare seed lots from different sites and collection dates. For these trials, 3 replications of 20 seeds each were used due to limited seed numbers. Significant differences occurred between seed lots collected at different sites with 2-52% germination for June and 43-95% germination for July. These findings demonstrate that sites differed in reproductive and seed characteristics, demonstrating the importance of conducting trials at multiple sites. This information should be useful for making management and federal listing decisions regarding Physaria kaibabensis.
|Original language||English (US)|
|Title of host publication||Botany 2016, Botanical Society of America Annual Meeting; 30 July -3 August 2016, Savannah, Georgia|
|State||Published - 2016|