HALL, SUZANNE S.1* and KAIUS HELENURM2. 1Department of Biology, San Diego State University, San Diego, CA 92182; 2Department of Biology, University of South Dakota, Vermillion, SD 57069. - Dissimilar patterns of genetic variation in two insular endemics with similar habitat, distribution, recent history, and species characteristics.
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