Habitat, Seed Dormancy, and Allozyme Variation of the Rare Endemic "Phacelia cookei" (Boraginaceae)

ABSTRACT HABITAT, SEED DORMANCY, AND ALLOZYME VARIATION OF THE RARE ENDEMIC Phacelia cookei (BORAGINACEAE) by Melissa E. Patterson Master of Science in Botany California State University, Chico Fall 2010 Experimental studies of rare species are the most effective way to create management strategies to conserve species and prevent further decline and extinction. We conducted habitat surveys, germination, and population genetic surveys to inform management priorities for Phacelia cookei Constance & Heckard (Boraginaceae), a diminutive annual herb only found within a three-mile radius near Mt. Shasta, California, and it is rare within that geographical range. Habitat surveys included a rapid vegetation assessment, soil samples, and assessment of ground cover. We found no significant differences among site category in soil types. An associated species list was created, and the most closely associated species was Nama densa A. Gray, which was found at four sites where P. cookei was present. We tested the effects of afterripening, scarification, stratification, and variable germination temperatures on breaking seed dormancy. Seed vii viability by tetrazolium tests ranged between 89% and 93%, but the highest germination from any treatment combination was 38.9% after adjusting for seed viability. We resolved 19 putative allozyme loci, only two of which were polymorphic. This species had low genetic diversity within and among the three large sampled populations when compared to other endemic species with similar mating systems, and this may ultimately be an important challenge for maintaining viable populations of the species. Management plans should consider additional studies to explore the feasibility of restoring populations in suitable locations by sowing seeds collected from existing populations is suitable habitat.