Systematic Investigations of True Thistles. NSF-funded studies of Cirsium phylogeny based on multiple lines of evidence (DEB-0344853) are continuing apace. Assistant Researcher Dean Kelch is spearheading this effort, which is an outgrowth of published work from the lab (Kelch & Baldwin 2003, see publication list) indicating that true thistles of the New World are a monophyletic group that underwent explosive ecological diversification following long-distance dispersal, much like an insular adaptive radiation and in strong contrast to previous ideas on evolutionary relationships within Cirsium.
Ongoing research in Compositae, supported in part by the National Science Foundation (DEB-9458237), the Lawrence R. Heckard Fund of the Jepson Herbarium, the Faculty Research Fund for the Biological Sciences at UC Berkeley, and Rod Park and other generous friends of the Jepson Herbarium:
Hawaiian silversword alliance evolution. We are refining our sampling of diversity in the silversword alliance and gene regions to obtain a more comprehensive view of relationships and diversification in the group. Recent work has allowed us to add previously unsampled bog endemics to our studies and to sample species that occur widely across their insular distributions.
Insular evolution, evolutionary modes, and phylogeny of Deinandra. As suggested earlier by Carlquist (1965), the perennial tarweeds of the California Islands show evidence of insular diversification. We are investigating modes and patterns of evolutionary change in these plants and their relationships to other, mainland members of Deinandra. As the only other example of insular evolution in Madiinae, the California Island deinandras offer an instructive comparison with the Hawaiian silversword alliance.
Contrasting modes of diversification in Layia. The tidy-tip genus Layia has been suggested to provide examples of gradual allopatric divergence ("geographic speciation") and rapid divergence of peripheral isolates ("peripatric speciation"). We are reinvestigating these hypotheses of Clausen, Keck, and Hiesey and subsequent researchers from molecular phylogenetic and biosystematic standpoints and extending their findings to include a set of cryptic, evolutionarily divergent lineages and related groups that provide a particularly striking example of unequal rates of phenotypic evolution.
Cytogenetic 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 cytogenetic 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).
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 polyploid evolution in Madia and additional insights on origin of the silversword alliance.
STUDIES IN MADIEAE OUTSIDE MADIINAE:
Collaborative phylogenetic and phylogeographic study of Arnica, with Katarina Andreasen (Uppsala University). We are examining biogeographic and ecological history and relationships in the circumboreal genus Arnica, revisiting Maguire's hypotheses and placing Wolf's cytogenetic data in a phylogenetic framework, with attention to the origin of unusual character states in A. (Whitneya) dealbata and A. mallotopus (Mallotopus japonicus).
Phylogenetic studies of Eriophyllum, Hulsea, and Monolopia. We are investigating 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. Don Kyhos and I are working toward an extended view of chromosome evolution and historical biogeography and ecology in Chaenactis, a goal that is now within reach with recent discovery that Dimeresia and Orochaenactis are close outgroups.
STUDIES IN BAHIEAE: We are now extending our earlier work on Bahia and relatives, to seek a more refined understanding of relationships in the Bahieae clade, wherein relationships have been misunderstood and provide a link to the South Pacific flora.