The Baldwin Lab

Evolution of California tarweeds, the Hawaiian silversword alliance evolution, and relatives in tribe Madieae. We have refined our sampling of diversity and gene regions in the California tarweeds, the silversword alliance, and the woolly sunflowers and relatives (e.g., Eriophyllum, Hulsea, Monolopia) to obtain a more comprehensive view of relationships and diversification in tribe Madieae. Expanded sampling of taxa coupled with target-enriched sequencing of hundreds of nuclear gene regions has been conducted to provide more resolution of evolutionary and biogeographic histories of these major Californian and Hawaiian lineages.

Insular evolution of Deinandra. As suggested by Carlquist (1965) and corroborated by our earlier studies, the perennial tarweeds of the California Islands show evidence of insular diversification. In collaboration with Jepson alumnus Matt Guilliams and the Santa Barbara Botanic Garden, we are seeking a more detailed understanding of evolutionary divergence and genetic differentiation within Deinandra clementina (island tarplant), an endemic of the northern and southern Channel Islands. The California Island deinandras offer an instructive comparison with the Hawaiian silversword alliance that we aim to extend by taking a closer look at fine-scale evolutionary patterns in the island tarplant.

Contrasting modes of diversification in Layia. The tidy-tip genus Layia has provided excellent examples of ecogeographic divergence and rapid divergence of peripheral isolates. We are continuing to investigate these evolutionary hypotheses of Clausen, Keck, and Hiesey and subsequent researchers from molecular phylogenetic and biosystematic standpoints. For example, we are examining fine-scale biogeographic and evolutionary patterns that have indicated additional diversity in the Layia gaillardioides (woodland layia) complex, considered a major example of ecotypic divergence by Clausen, Keck, and Hiesey. In collaboration with Jepson alumnus Isaac Lichter-Marck (California Academy of Sciences), Ryan O’Dell (CA-BLM), Susan Fawcett (UC/JEPS), and the California Conservation Genomics Project (CCGP), we also are examining whole nuclear genomes in ~100 populations of the Layia glandulosa complex to gain better evolutionary understanding of the serpentine endemic L. discoidea and other edaphically unusual layias.

Biosystematic and phylogenetic studies in the spikeweeds (Centromadia). The spikeweeds show evidence of recent divergence accompanied by chromosomal repatterning and dysploidy. We are investigating the evolution of these changes using biosystematic and molecular phylogenetic data, with special attention to previously undetected evolutionary diversity in the group.

"Chromosome evolution paradox" in Calycadenia. In collaboration with Gerry and Bob Carr, we are working on refining understanding of a sharp contrast in relatives rates of chromosomal and morphological evolution in sister lineages of Calycadenia, originally proposed by Gerry Carr. A clock-like molecular phylogeny of the clade encompassing Calycadenia multiglandulosa and Calycadenia pauciflora is allowing a time-based perspective on evolutionary rates in the two groups, which show either extensive morphological divergence with no fixation of new chromosome arrangements (C. multiglandulosa complex) or extensive chromosome evolution and minimal morphological change (C. pauciflora complex). These studies also have revealed additional diversity within Calycadenia that we seek to describe.

Molecular phylogenetic investigations of Hemizonia, Holocarpha, Lagophylla, the "Madia" lineage. We are revisiting Babcock & Hall's phylogenetic and biogeographic hypotheses for Hemizonia s.s., Clausen, Keck, & Hiesey's and Palmer's ideas on chromosomal evolution in Holocarpha, and Thompson's (1983) evolutionary hypotheses for Lagophylla. In the Madia lineage, we are seeking refined understanding of diversity in Carlquistia, polyploid evolution in Madia, and additional insights on origin of the silversword alliance.

STUDIES IN MADIEAE OUTSIDE MADIINAE:

Phylogenetic studies of Eriophyllum, Hulsea, and Monolopia. We are continuing to investigate relationships, historical biogeography, and historical ecology in Eriophyllum, Hulsea, and Monolopia to understand how evolutionary change in these diverse lineages compares to patterns seen in the closely-related tarweeds, arnicas, and goldfields.

STUDIES IN CHAENACTIS: Chaenactis provides outstanding examples of chromosome patterning and polyploidy, in part associated with ecological shifts and dispersal. We are continuing our work toward an extended view of chromosome evolution and historical biogeography and ecology as well as overall diversity in Chaenactis, a goal that is now within reach with discovery that Dimeresia and Orochaenactis are close relatives.