Restoration of a rare hemiparisitic plant: California’s seaside bird’s beak, Cordylanthus rigidus ssp littoralis

Seaside bird’s beak, Cordylanthus rigidus ssp. littoralis (C.r.l.; Scrophulariaceae), a California endangered subspecies, presents particular challenges to reserve managers. As a hemiparasitic annual herb, it receives much of its water and nutrients from perennial hosts and may have related germination requirements. With a series of experiments focused on three critical life history stages we seek to prioritize conservation and restoration efforts directed at the last few remaining populations of C.r.l. Germination: The application of baked and ground chaparral shrub stems (charate) has occasionally proven beneficial to the germination of fire-adapted plants in sites that are no longer regularly burned. We are currently measuring the effectiveness of this method for C.r.l. plants (and other rare native annuals). Growth: We fenced patches of C.r.l. to exclude rabbits and deer, which significantly increased plant size and reproduction relative to un-caged plants. Mammalian herbivores appear to be at elevated densities inside the reserve where we conducted our studies. Seed Predation: Applying a short-lived insecticide (Bt) to flowering individuals significantly reduced damage from Lepidopteran seed predators. Although patches of C.r.l. can be extremely dense (up to 227 individuals per m²), the remaining populations are small and isolated. C.r.l. seeds do not display any mechanism to enhance dispersal, implying that the establishment of new populations will require assistance. With high densities of plant enemies and the special habitat requirements of C.r.l., reserve managers now recognize the importance of herbivore and seed predator exclusion to the success of any restoration attempts.