MCMAHON, MICHELLE* and LARRY HUFFORD. School of Biological Sciences, Washington State Unversity, Pullman, WA 99164-4236. - Phylogeny of Amorpheae (Fabaceae: Papilionoideae) inferred from matK and ITS.
Uncovering the patterns of morphological diversity in clades is
essential to evolutionary biology. Among the 12,000 species of
subfamily Papilionoideae, pea-like flowers are highly conserved. In
the tribe Amorpheae, however, they have been lost and flower forms are
highly diverse. To understand the origin of morphological diversity in
Amorpheae, we have constructed a phylogenetic hypothesis using DNA
sequence data from the chloroplast gene trnK and its intron, including
the gene matK. Our data, consistent with our previously reported
results, strongly support the monophyly of Amorpheae, as well as
several clades within Amorpheae. The genera Psorothamnus,
Dalea, and Marina are united by sharing a generally
papilionoid form, and are supported as a clade. Within this clade,
Dalea and Marina are supported as a clade, nested within
a paraphyletic Psorothamnus. This result corresponds to
predictions we made in studying an unusual petal-stamen
synorganization found in Dalea, Marina, and some
Psorothamnus. To further resolve relationships within the large
genus Dalea and among the closely related genera
Amorpha, Errazurizia, and Eysenhardtia, we have
added data from the nulcear ITS region. Our analysis of ITS data
produced very little conflict with the matK data. For example,
Dalea filiciformis is placed as sister to Marina by both
data sets. In addition, for the taxa sampled, ITS data resolve
relationships between species groups. For example, ITS data strongly
support the traditional subgenera Dalea and Parosela.
This is predicted by morphology: flowers in Dalea subgenus
Dalea generally have unfused corollas, whereas subgenus
Parosela tend to have corollas that include a "keel"
(two petals marginally fused) that encloses the reproductive
structures. The addition of ITS data to our previously acquired matK
data allows us to study Amorpheae floral form evolution in greater
detail by providing more resolution than with matK alone.
Key words: Amorpheae, Fabaceae, floral evolution, ITS, matK, phylogeny