Graduation Date
Spring 2024
Document Type
Thesis
Program
Master of Science degree with a major in Biology
Committee Chair Name
Oscar Vargas
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Jeffrey White
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Erik Jules
Third Committee Member Affiliation
HSU Faculty or Staff
Fourth Committee Member Name
Eric LoPresti
Fourth Committee Member Affiliation
Community Member or Outside Professional
Keywords
Abronia, Abronia villosa var. aurita, Evolution, Systematics, California Floristic Province, Microevolution, Budding speciation, Budding divergence, Biogeography, Genetics, Phylogenetics, Ecological speciation, Progenitor, Derivative
Subject Categories
Biology
Abstract
Physical barriers to gene flow are the traditional evidence for species divergence. Conversely, there has been increasing acknowledgment of speciation in the face of gene flow as an evolutionary process. Budding speciation involves peripheral populations adapting to local ecological conditions, thereby budding off from a widespread progenitor species. Budding speciation is distinguished by ecological divergence and is generally evidenced by asymmetrical range size and nested phylogenetic relationships of sister species. The narrow endemic Abronia villosa var. aurita is adapted to montane sandy washes adjacent to its widespread sister variety, the desert dwelling var. villosa. Here, I tested the hypothesis that A. villosa var. aurita is derived from its sister variety via budding divergence. My investigation employed phylogenomic and genetic structure analyses of a clade comprised of A. villosa and its close allies, A.umbellata and A. gracilis. My results reveal that Abronia villosa var. aurita is a recently budded taxon, phylogenetically nested within its sister variety yet still showing unique genetic structure. Unexpectedly, I found evidence that var. aurita comprises two reciprocally monophyletic subclades, separated by an elevational gradient. I also confirmed Tillet’s 1967 hypothesis that A. villosa would hybridize with the coastal A. umbellata in the localities where they are sympatric. Ultimately, my study shows a recent but complex history of divergence and subsequent post-divergence processes, illustrating the importance of capturing nuanced snapshots of microevolutionary mechanisms as they occur.
Citation Style
APA
Recommended Citation
Allen, Eli J., "A case of incipient budding speciation in the California Floristic Province, infraspecific divergence in Abronia Villosa" (2024). Cal Poly Humboldt theses and projects. 746.
https://digitalcommons.humboldt.edu/etd/746
Included in
Biology Commons, Computational Biology Commons, Evolution Commons