Field and Genetic Survey of the Endangered Butte County Meadowfoam—Limnanthes floccosa subsp. californica (Limnanthaceae)

The Butte County meadowfoam ( Limnanthes floccosa subsp, californica ), an endangered annual endemic to vernal pools in Butte County, California, is of agronomic interest as a sperm whale oil substitute. Because it is threatened by rapid development of the community of Chico, a field and genetic survey was required to guide a conservation program. Eight new populations were discovered, bringing the total known to eleven. Population sizes varied from 220 to 45,689 plants; mean seed set per flower, a bioassay of site quality, ranged from 0.82 to 2.56 among populations. The array of associated taxa, an indicator of appropriate habitat was fairly uniform across populations. Based on allozyme and morphometric data no introgression between L. floccosa subsp, californica and L. alba subsp, alba at sympatric sites was found. Populations were remarkably monomorphic, probably due to past population bottlenecks in conjunction with high selfing rates. Electrophoretic analysis of 28 isozyme loci revealed that 96% of total genetic diversity was distributed among populations. The migration rate, Nm , calculated from the mean frequency of private alleles, ( P (1)), and from the proportion of genetic variation distributed between populations, Gst , estimated exchange between local populations of one diploid individual every 50 to 100 generations, respectively. Mean genetic identity among populations was 0.91 ± 0.068. Grouping of populations on the basis of genetic distance identified two distinct populations and three clusters of populations that deserve high priority for preservation because they are likely to have high frequencies of locally adapted alleles. The low migration rates and substantial differentiation among populations suggest a conservation plan that emphasizes preservation of as many populations as possible, at possible expense of numbers of individuals.