MCMAHON, MICHELLE* AND LARRY HUFFORD. School of Biological Sciences, Washington State University, Pullman, WA 99164-4236. - Phylogeny of Amorpheae (Fabaceae:Papilionoideae) based on DNA sequences from the chloroplast trnK intron, including the matK gene.
Floral evolution in the legume tribe Amorpheae (eight genera, c. 240
species) has involved dramatic changes in the number, shapes, and
positions of floral organs, including an unusual corolla-androecium
synorganization. To study floral evolution in the tribe, we have
reconstructed the phylogeny of the group, sampling heavily from genera
for which we have morphological evidence that calls monophyly into
question. Our preliminary results indicate that there are two major
lineages, one consisting of three genera (Dalea, Marina,
Psorothamnus) and the other of four (Parryella,
Eysenhardtia, Errazurizia, Amorpha); the
placement of monotypic Apoplanesia is uncertain. The first of
these major clades includes floral diversity encompassing limited
variation in the "papilionoid" floral form, but includes all
cases of the corolla-androecium synorganization. The second clade
includes a surprising level of diversity in petal number and floral
symmetry. Psorothamnus is paraphyletic due to the placement of
dalea-like P. emoryi as sister to Dalea plus
Marina. Marina is supported as monophyletic, however
Dalea is not. Dalea filiciformis shares many
morphological characteristics with Marina and our results show
that it is well supported as the sister group to Marina. The
underused non-coding regions of the trnK intron (i.e., outside
the coding region for matK) provided many variable and
informative sites for resolving these relationships. Our well
supported phylogeny of Amorpheae at the generic level provides a firm
basis for refining classification of the tribe and analyzing processes
generating floral diversity.
Key words: Amorpheae, Fabaceae, floral evolution, matK, phylogeny