Camissonia guadalupensis ssp. clementina (Onagraceae) and Cryptantha traskiae (Boraginaceae) are insular endemics identified as Species of Concern (USFWS). Camissonia g. clementina is known only from San Clemente Island, California (10 populations), while Cryptantha traskiae is known from both San Clemente Island (9 populations) and San Nicolas Island (~ 3 populations). Both taxa show strong habitat specificity, occurring only on sandy coastal flats and partially stabilized sand dunes. Although not closely related phylogenetically, they share recent history by virtue of being endemic taxa that co-occur at nearly all of the locations where they are found. In addition, they share other characteristics affecting patterns of genetic variation such as an annual habit, a primarily selfing mating system, and passive seed dispersal. All populations of the two taxa on San Clemente Island were surveyed for genotypes at 16 allozyme loci, revealing generally low levels of genetic variation. Camissonia has higher levels of variation than Cryptantha at both the taxon (P = 37.5 vs. 18.8, A = 1.69 vs. 1.31, and HE = 0.088 vs. 0.003) and population levels (P = 8.8 vs. 3.5, A = 1.09 vs. 1.03, and HE = 0.017 vs. 0.003), although some populations of each taxon are monomorphic at all loci. Locations of the more variable populations of each species do not coincide. A greater proportion of variation is found among populations of Camissonia (GST = 0.810) than among populations of Cryptantha (GST = 0.042). Clear differences exist in patterns of genetic variation in the two taxa despite their shared habitat, distribution, recent history, and species characteristics.

Key words: allozymes, Camissonia, conservation, Cryptantha, endemic, genetic variation