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Two genera of Brassicaceae – Lesquerella and Physaria – were recently united on the basis of monophyly. Classically, these genera have been distinguished based on morphology with 'traditional” Physaria species having doubly inflated (didymous) fruits. Molecular data consisting of ribosomal internal transcribed spacer (ITS) DNA sequences indicate Physaria has evolved from the larger Lesquerella genus, thus making Lesquerella a paraphyletic grouping as previously described. A revised treatment of the combined Physaria recognized 106 species within the genus, of which 26 taxa occur in Wyoming. Of the Wyoming taxa, those traditionally described as belonging to Physaria (i.e.Physaria sensu stricto) have been identified as needing taxonomic investigation. The evolutionary relationships of these species is considered based on molecular, geographical, and morphological data. Three groups of particular interest include the status of P. vitulifera in south-central Wyoming; the relationships of reportedly sympatric P. saximontana and P. eburniflora to P. didymocarpa subspecies; and the status of regional and state endemics P. integrifolia, P. condensata, and P. dornii. 1665 herbarium specimens were reviewed for taxonomy and morphological data for discrete and continuous characters were recorded. Geographical data in the form of TRS or specific location descriptions from specimen vouchers were converted to degree decimals and species distributions were mapped using open source R packages. Nuclear ribosomal ITS DNA and plastid rps intron and ycf1 were sequenced from Physaria sensu stricto individuals throughout the respective distribution of each species. Phylogenetic analysis of individual gene and multi-locus concatenated data by Bayesian inference did not recover strong support for monophyletic groupings of these taxa as previously described. Furthermore, a high degree of intragenic sequence similarity between individuals supports a recent divergence of these taxa. Geographic data reveal a high elevation distribution of contested P. vitulifera specimens from south-central Wyoming with an apparent allopatric relationship to proximal species P. floribunda and P. vitulifera. This lineage is hypothesized here as Physaria ’medicinae’ on the basis of phylogenetic support, reduced fruit size and growth habit, and elevation gradient. The primary distinguishing fruit characteristic of P. saximontana subsp. saximontana is shown to be prevalent among P. didymocarpa subspecies didymocarpa specimens of Montana, supporting a status change with precedence to the earlier described taxa. Molecular data also support close relationships between the regional and state endemics of south-western Wyoming, suggesting a polyphyletic relationship as currently described.

Year of Submission


Degree Name

Master of Science


Department of Biology

First Advisor

Steve O'Kane, Chair

Date Original


Object Description

1 PDF file (vii, 160 pages)

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.



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