CHAN, RAYMUND*, BRUCE G. BALDWIN, and ROBERT ORNDUFF. Jepson Herbarium and Department of Integrative Biology, University of California, Berkeley, CA 94720. - Cryptic diversity in the goldfield Lasthenia californica sensu lato (Compositae: Heliantheae sensu lato).
Lasthenia sect. Baeria, one of six sections recognized
by Ornduff (1966) in Lasthenia, includes the most common and
geographically widespread goldfield species L. californica.
Previous biosystematic studies using morphology, flavonoids, and
isozymes have not revealed any unequivocal lineages within this
morphologically and ecologically highly variable taxon. Maximum
parsimony analysis of DNA sequence data from the internal and external
transcribed spacers of 18S-26S nuclear ribosomal DNA, and the 3' end
of the matK coding gene and adjacent 3' trnK intron of
chloroplast DNA from over 60 populations of L. californica and
close relatives yielded a well-supported tree showing that L.
sect. Baeria is monophyletic only with the inclusion of L.
leptalea, previously placed in L. sect. Burrielia.
Most importantly, this tree also resolves L. californica to be
a non-monophyletic group that represents two robustly supported
clades. One clade includes L. macrantha; the other may be
sister to L. sect. Baeria. Each of the two groups can be
diagnosed by pappus morphology (although some individuals are
epappose) and to some extent by geographic distribution. We have
recognized these two clades of L. californica as distinct taxa.
The molecular results also show that the overall diversification in
the clade corresponding to L. sect. Baeria plus L.
leptalea has been accompanied by minimal morphological divergence,
which has resulted in previously underappreciated cryptic diversity.
Key words: cryptic diversity, external transcribed spacer, internal transcribed spacer, Lasthenia californica