Goldfields Revisited: A Molecular Phylogenetic Perspective on the Evolution of Lasthenia (Compositae: Heliantheae sensu lato)

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences. DNA sequence data from the internal and external transcribed spacers of 18S-26S nuclear ribosomal DNA and the 3 trnK intron of chloroplast DNA provide evidence for patterns of evolutionary diversification and relationships in Lasthenia. Maximum parsimony analysis shows strong support for monophyly of Lasthenia and monophyly of each of seven sections (as treated here) in Lasthenia, with minor revision of Ornduff's (1966) sectional circumscriptions. Lasthenia sect. Amphiachaenia (correct name for L. sect. Baeria sensu Ornduff 1966 and redelimited to include L. leptalea) was resolved as a basally divergent section, i.e., as the sister group of a clade comprising all other Lasthenia taxa. Placement of other sections within Lasthenia is only weakly resolved, except for L. sect. Burrielia (redefined to exclude L. leptalea) and L. sect. Hologymne, which are robust sister clades. The clade comprising L. sect. Burrielia and L. sect. Hologymne and clades corresponding to each of the other sections except L. sect. Amphiachaenia constitute a polytomy, with most clades characterized by a long basal branch and relatively short terminal branches. We suggest that overall patterns of divergence in the molecular trees for Lasthenia conform to expectations of saltational diversification, with an initial rapid radiation followed by long periods of minimal diversification in each group preceding relatively recent episodes of speciation. Results also show that several important taxonomic characters in Lasthenia are homoplastic and that the base chromosome number for Lasthenia is xp8.

The Edaphic Factor in the Origin of Plant Species

“…A recent phylogenetic study (Chan et al, 2001) shows a close relationship between the two species, but does not conclusively support Ornduff's (1966) and Crawford et al's (1985) proposed ancestordescendent relationship. Nevertheless, the close relationship between the two species is reflected by the high fertility of artificial crosses (Ornduff, 1966).…”

“…ex Lindl. and L. gracilis (DC) Greene (Chan et al, 2001(Chan et al, , 2002. Previous research had shown that there are two edaphic races within this complex, with one race (A) occupying ionically extreme soils such as serpentinite outcrops, coastal bluffs, alkaline flats, and the other (C), occupying ionically moderate yet waterstressed soils (Rajakaruna and Bohm, 1999).…”

Parallel Ecological Speciation in Plants?

“…Race A grows on ionically extreme habitats such as coastal bluffs, alkaline flats, vernal pools, and serpentine soil, while race C is found on ionically benign and drier locations such as pastures and oak woodlands. Phylogenetic analyses using ribosomal and chloroplast sequences along with allozyme variation indicate two cryptic clades within the species with representatives of both races in each [81][82][83][84], suggesting a parallel origin of each race. Greenhouse experiments indicate that race A plants, regardless of phylogenetic clade, have greater tolerance to Na + and Mg 2+ and in drought conditions race C plants flower earlier and produce more flower heads [85,86].…”

“…Lasthenia californica has strong evidence for parallel evolution of two races that have different flavonoid pigments and are found in different edaphic environments using phylogenetic analyses of ribosomal and chloroplast sequence and allozyme variation [81][82][83][84]. Race A is more tolerant of Na + and Mg 2+ and race C flowers earlier and produced more seed heads under drought conditions [85,86].…”

Pollinator Response to Patch Distribution and Reproductive Consequences in Lasthenia californica

“…L. californica was chosen for this study for its self-incompatibility and strong reliance on animals for pollination (Chan et al, 2011). Its range stretches from southern Oregon to southern California and is frequently found in wetland and prairie habitats.…”