EVOLUTION AND DIVERSITY OF MALACOTHRIX AND RELATIVES (CICHORIEAE; COMPOSITAE), WITH SPECIAL REFERENCE TO TAXA OF CALIFORNIA'S CHANNEL ISLANDS

Cytogenetic and morphological data bring additional evolutionary context to a molecular phylogenetic study of the primarily western North American Malacothrix DC. and relatives (Cichorieae; Compositae) based on nuclear ribosomal (nr)DNA sequences. One of two major clades resolved includes the M. foliosa A.Gray complex, an insular radiation with all taxa native to the Channel Islands and all but one (M. incana (Nutt.) Torr. & A.Gray) endemic there or to the California Islands more generally. Diploids of the M. foliosa complex mostly retain high interfertility and are isolated geographically or ecologically, although recent introduction of M. incana to San Nicolas Island has resulted in extensive hybridization with single-island endemic M. foliosa subsp. polycephala W.S.Davis. Based on cytogenetic, morphological, and molecular phylogenetic results, the tetraploid M. junakii W.S.Davis, endemic to Middle Anacapa Island, is evidently an allopolyploid from hybridization between diploids in the M. foliosa and M. clevelandii A.Gray complexes. Tetraploid M. squalida Greene, endemic to Anacapa and Santa Cruz islands, and M. insularis Greene, endemic to Las Islas Coronado, Mexico, are evidently closely related to the widespread diploid M. coulteri Harv. & A.Gray, which represents a distinct lineage from the above complexes and is one of two subgenomes in M. squalida based on cytogenetics and morphological considerations. The other major clade in Malacothrix includes the perennial M. saxatilis (Nutt.) Torr. & A.Gray complex of highly interfertile, allopatric or putatively ecologically divergent diploids, wherein the Channel Islands endemic M. saxatilis var. implicata (Eastw.) H.M.Hall is evidently sister to the other varieties. Insular endemics across Malacothrix (except in M. saxatilis) and their close mainland relatives are self-compatible, at least in part, in keeping with Baker's Rule. Island endemics of the diverse M. foliosa complex generally have cypselae exemplifying the insular syndrome of reduced dispersibility, having lost outer pappus, unlike almost all primarily mainland taxa (except M. floccifera (DC.) S.F.Blake), including those inferred to have been bird-dispersed from North to South America (M. clevelandii, M. coulteri). Expanded circumscription of Malacothrix to result in generic monophyly requires reinstating Malacothrix platyphylla A.Gray and the new combinations Malacothrix acaulis (Torr. & A.Gray) B.G.Baldwin & Joongku Lee, Malacothrix parryi (A.Gray) B.G.Baldwin & Joongku Lee, and Malacothrix wrightii (A.Gray) B.G.Baldwin & Joongku Lee for all taxa previously in Anisocoma Torr. & A.Gray, Atrichoseris A.Gray, and Calycoseris A.Gray.