A Phylogenetic Study of Sanicula sect. Sanicoria and S. sect. Sandwicenses (Apiaceae) Based on Nuclear rDNA and Morphological Data

Abstract

Parsimony analysis of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences and morphological data provided a well-resolved set of phylogenetic hypotheses for Sanicula, with special emphasis on the western American species constituting sect. Sanicoria and the Hawaiian sect. Sandwicenses. A lineage that encompasses the western American sect. Sanicoria and the Hawaiian sect. Sandwicenses appears to comprise three major clades: Clade 1, a group of coastal North American and Hawaiian species; Clade 2, an ecologically diverse assemblage of continental taxa including maritime, marsh, chaparral, serpentine, and desert species; and Clade 3, a group of mostly narrowly-endemic species of interior habitats in western North America. Species of the largely Old World sect. Pseudopetagnia and sect. Sanicula fall outside the sect. Sanicoria + sect. Sandwicenses clade. The (weakly supported) phylogenetic patterns among species of sect. Pseudopetag- nia and sect. Sanicula are consistent with an Asian origin of Sanicula. As reported earlier, three primarily- Californian, coastal species of sect. Sanicoria (S. arctopoides, S. arguta, and S. laciniata) appear to be more closely related to the monophyletic Hawaiian group than to other members of sect. Sanicoria. Biogeographic recon- structions provide unequivocal support for dispersal of the Hawaiian ancestor from the California Floristic Province. Estimates of clade age from rate-constant ITS trees place the most recent common ancestor of the Hawaiian taxa at ? 0.9 ? 0.4 Ma, after the origin of Kaua'i, O'ahu, and West Maui, but indicate a divergence from the closest surviving American lineage at ? 8.9 + 1.5 Ma, i.e., possibly before the origin of the modern high islands. Our data confirm that the two South American species of sect. Sanicoria are conspecific with western North American S. crassicaulis and S. graveolens and originated from a minimum of two long-distance dispersal events < 2.5 Ma (since the late Pliocene). A suite of fruit characteristics that promote animal dispersal are common to the Hawaiian and South American species and their closest North American rela- tives. Dispersibility appears to have been lost multiple times in western North America, with limited diver-