Astragalus oniciformis Barneby is a xerophyte of the sagebrush deserts of
central Idaho. It is a narrow endemic of the upper Snake River Plains
where it inhabits stabilized, aeolian sand deposits over Quaternary basalt
flows. The objective of this study was to determine the levels and
distribution of genetic differentiation within and among populations of
Astragalus oniciformis. Fifteen individuals from each of eight populations,
chosen from throughout the range of the species, were selected for their
accessibility, density of individuals, and large population size. Two
disjunct eastern populations selected for this study have been separated
from the continuous western populations for 3600 years by an eight-mile
wide, inhospitable lava flow. Inter-simple sequence repeats (ISSR) were
chosen as the marker to assess genetic differentiation. Two primers were
selected that yielded 40 loci, all of which were polymorphic in A.
oniciformis. In an analysis of molecular variance (AMOVA), 88.69 percent
of the variation was significantly attributed to variation within populations.
The differentiation between the two disjunct populations and the western
populations was insignificant. High gene flow (Nm=3.91-3.93) and a low
percent deviation from Hardy-Weinberg equilibrium due to population
subdivision (G[subscript st]=0.113-0.1134) were found among populations of A.
oniciformis. These results suggest that current threats to this species,
ranging from plant community changes due to changing fire patterns,
habitat alteration from livestock grazing, and habitat loss from agricultural
development have not yet affected the genetic diversity of this species.
Preservation of the numerous, large populations and the high gene flow
will help insure that the levels of genetic diversity found in Astragalus
oniciformis will not decrease. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/30006 |
| Date | 14 May 2001 |
| Creators | Alexander, J. Andrew |
| Contributors | Liston, Aaron I. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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