Helenurm, Kaius .
Distinctive pattern of genetic diversity in the insular endemic plant Astragalus nevinii (Fabaceae).
Astragalus nevinii, a perennial herb endemic to San Clemente Island, California, is known from few populations because it is limited to sandy and caliche soils. Electrophoretic data for 23 loci were collected from twelve populations. Across all populations, a majority (60.9%) of loci are polymorphic with AP=2.29 and HE=0.022. Populations average only 17.0% polymorphic loci with AP=2.07 and H E=0.020. All polymorphic loci have the same common allele in all populations and one or two alternative alleles that are nearly exclusively rare (q<0.05), and distributed across only a few, often adjacent populations. Populations vary at least three-fold in measures of genetic variation, but variation within populations is not correlated with current population size. Most variation is found within rather than among populations (GST=0.094) although differentiation among populations is significant. Genetic identities are high, ranging from 0.990 to 1.000 with mean I=0.998. There is no significant relationship between genetic and geographic distance, and the pattern of genetic variation is not concordant with the geographic pattern of populations. Gene flow among populations is Nm=8.8 based on private alleles and Nm=2.4 based on FST. Outcrossing rates based on fixation indices average t=0.58, indicating a mixed mating system.
1 - University of South Dakota, Department of Biology, 414 East Clark Street, Vermillion, South Dakota, 57069, USa
San Clemente Island.
Presentation Type: Paper
Location: Peruvian (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 10:45 AM