Date of Award

12-2020

Document Type

Thesis

Degree Name

Master of Science in Biology

Department

Biology

First Reader/Committee Chair

Metcalf, Anthony

Abstract

Studies on population genetics examine the relationship and effects of population structure, migration, gene flow and demographic history, and are therefore important in the conservation of endangered species. Astragalus jaegerianus, a critically federally endangered species found in a geographically restricted range is investigated to determine population structure and genetic variation. Previous research on A. jaegerianus focused on DNA sequence data for cpDNA and nrDNA showed no variation. Further research on A. jaegerianus utilizing AFLP’s on the whole genome indicated substantial gene diversity and population structure consistent with geographically widespread species. AFLP research is a cost-effective process to identify levels of genetic diversity but does not allow determination of heterozygosity or homozygosity. However, microsatellite analysis identifies tandem base pair repeats, which are co-dominant markers, and heterozygotes can be determined from homozygotes. Through Illumina paired-end shotgun sequencing, 26 microsatellites were isolated and characterized for A. jaegerianus. Loci were screened across 24 individuals in 5 subpopulations. The 26 identified microsatellites underwent preliminary screening to determine the 7 optimal primers for this study.

Of the 176 initial samples, 140 individuals successfully amplified across a minimum of 4 microsatellite loci. Microsatellite analysis supports Walker and Metcalf’s (2008) findings of population structure and genetic variation comparable to geographically widespread plant species. The RST values ranged from 0.010 to 0.328, indicating that Brinkman Wash is the most distinct of the populations. In comparing the STRUCTURE analysis to the outcome of the PCoA, the data indicate there are four distinct populations and that Coolgardie Mesa and Lane Mountain appear to be more similar and can be viewed as a single population. Both AFLP and microsatellite analyses support the findings that Astragalus jaegerianus has maintained a high level of genetic diversity despite the limited range and reduced population size.

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