BROWN, GREGORY K.* and DOROTHY E. TUTHILL. Department of Botany, University of Wyoming, Laramie, Wyoming, 82071. - Inter-simple sequence repeat (ISSR) variation in three populations of Gaura neomexicana ssp. coloradensis (Onagraceae).
Gaura neomexicana ssp. coloradensis, commonly known as the Colorado
butterfly plant, is a regional endemic restricted to approximately
1700 acres of habitat in Laramie County, Wyoming, western Kimball
County Nebraska, and Weld County, Colorado. The taxon was recently
listed as Threatened under the Endangered Species Act (U.S. Fish and
Wildlife Service, October 2000). The three largest populations of G.
neomexicana ssp. coloradensis are confined to F.E. Warren Air Force
Base, Cheyenne, Wyoming, and are known in the literature as the Crow
Creek, Diamond Creek, and "unnamed drainage" populations.
For each population, DNA samples were obtained from 50 different
randomly selected individuals. An initial survey of ISSR locus
variation, using three primers on the entire sample of 150, revealed
very low levels of variation, both within and between populations. In
an effort to reveal additional ISSR locus variation, subsets of eight
individuals were randomly chosen from each population sample of 50.
The reduction of sample size from 150 to 24 permitted examination with
more ISSR primers. A total of 12 ISSR primers were applied to the
sample of 24, revealing 88 loci. A sample-by-locus matrix was
constructed, and loci were scored as present or absent (or as missing
data if PCR failed). The matrix contained 3.4% missing data, with most
coming from one individual. Results from cluster analysis revealed a
high level of genetic similarity (0.88) across the entire sample, and
no similarity clustering by population. The apparent ISSR locus
homogeneity across these three populations was not unexpected. Prior
to the establishment (1867), and subsequent expansion of the military
base, these three populations were very likely lobes of a larger,
Key words: Gaura neomexicana ssp. coloradensis, ISSR, Onagraceae, rare species