Date of Award

Fall 2022

Degree Type

Restricted to Claremont Colleges Dissertation

Degree Name

Botany, PhD



Advisor/Supervisor/Committee Chair

J.Mark Porter

Dissertation or Thesis Committee Member

J.Travis Columbus

Dissertation or Thesis Committee Member

Naomi Fraga

Terms of Use & License Information

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

Rights Information

© 2022 Keir Morse

Subject Categories



Malacothamnus (Malvaceae) is a genus of fire-following shrubs found primarily in the California Floristic Province. The taxonomy of the genus has been controversial for many years due to conflicting treatments, which recognize between 11 and 28 taxa. Many taxa of conservation concern are not recognized in some of these treatments, which makes resolving taxonomic questions in the genus a conservation priority. To resolve these questions, I use a combination of morphological, geographic, and phylogenetic evidence. Morphological measurements of specimens were first analyzed with principle component analysis (PCA), pairwise permutational multivariate analysis of variance (PERMANOVA), and linear discriminant analysis (LDA) to answer (1) whether taxa relegated to synonymy by some authors are morphologically distinct or not, (2) whether there is morphological evidence to support purported intergradation between taxa, (3) whether previously defined morphological boundaries between taxa are justifiable or need refining, and (4) whether populations of hypothesized novel taxa are morphologically distinct from the taxa they have been included within. Thirty-eight morphological groups with varying levels of distinctness were recovered and used as hypothesized lineages to be tested in a phylogenetic framework using a restriction site-associated DNA sequencing (RADseq) dataset. Samples were analyzed using maximum likelihood analysis, quartets-based species tree analysis, neighbor-net analysis, and multidimensional scaling. Based on the totality of evidence, a new treatment of the genus is proposed recognizing 30 taxa in 22 species. This treatment includes life history, discussion and illustrations of morphological characters useful in identification, and conservation information relevant to the genus. A key to all taxa is presented, followed by morphological descriptions, synonymy, common names, typifications, distribution maps, phenology, conservation status, notes, and photographs.


This dissertation has been revised, peer-reviewed, and self-published into three volumes through Figshare here:



Available for download on Wednesday, January 22, 2025