Date of Award:

12-2010

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Advisor/Chair:

John G. Carman

Abstract

Western prairie clover [Dalea ornata (Douglas ex Hook.) Eaton & J. Wright] is a perennial legume that occurs in the northern Great Basin, Snake River Basin, and southern Columbia Plateau, whereas Searls prairie clover [Dalea searlsiae (A. Gray) Barneby], also a perennial legume, occurs in the southern Great Basin and surrounding areas. Understanding the genetic and ecotypic variation of these prairie clovers is a prerequisite for developing populations suitable for rangeland revegetation in the western USA. DNA sequences of internal transcribed spacer (ITS/5.8S) and trnK/matK were used to study the phylogeny of these species. The species were distinguished by DNA sequences from both regions and conserved haplotypes were observed between and within species. Common-garden plots of 22 collections of western prairie clover from Idaho, Oregon, and Washington and 20 collections of Searls prairie clover from Utah and Nevada were established in northern Utah for phenotypic evaluation. Significant variation was detected among the collections for all traits measured in the common gardens for both species. Flowering date was correlated with collection-site temperature and elevation in western prairie clover collections, whereas biomass-related traits were closely related with collection-site precipitation in Searls prairie clover. Population structure from amplified fragment length polymorphism (AFLP) markers resulted in two distinct, genetically differentiated groups and a third admixed group in western prairie clover, and flowering date played a significant role in discriminating those genetic-based groupings of collections. For western prairie clover, two populations are recommended for development, one from the Deschutes River watershed and another from the remaining collections. For Searls prairie clover, two genetically different groups of collections were identified from southern Utah and eastern Nevada and from northwestern Utah. Three western Nevada collections exhibited close association with eastern Nevada and southern Utah groups for AFLP-markers but with collections from northwestern Utah for phenotypic traits. Strong isolation by distance was observed for Searls prairie clover collections suggesting that genetic drift and gene flow are major factors for determining population structure in this species. As a result, two regional seed sources should be developed for Searls prairie clover, one from northwestern Utah and the other from eastern Nevada and southern Utah.

Comments

This work made publicly available electronically on December 23, 2010.

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