PELL, SUSAN K.* and LOWELL E. URBATSCH. Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803. - Tribal relationships and character evolution in the cashew family (Anacardiaceae): inferences from three regions of the chloroplast genome.
The cashew family, Anacardiaceae, includes about 600 species and has
traditionally been subdivided into five tribes (Anacardieae, Dobineae,
Rhoeae, Semecarpeae, and Spondiadeae). Results from analysis of
sequence data for matK, trnL, and the intergenic spacer between the
trnL exon and trnF indicate that this five tribal system is artificial
and instead supports two major clades within the family. The larger
clade contains members of tribes Rhoeae, Semecarpeae, Dobineae, and
Anacardieae while the smaller clade contains tribe Spondiadeae and a
few members of tribe Rhoeae. The results, generated from sequence data
for these three regions of the chloroplast genome, also support a
monophyletic Anacardiaceae, distinct from its sister group, the
Gumbo-Limbo family, Burseraceae. The sequence data appear congruent
with floral structure characters that distinguish these two families.
Within each of the families floral structure is relatively uniform but
Anacardiaceae differs from Burseraceae by the number and orientation
of the ovules. Conversely, fruit type in Burseraceae is rather
invariable while Anacardiaceae has a wide variety of fruit types.
There are many unusual fruit characteristics found within the cashew
family, such as, the presence of specialized seed germination
structures known as opercula and a diversity of evolutionary
adaptations for wind dispersal. Preliminary phylogenies generated in
this study indicate that opercula have evolved twice and wind
dispersed taxa group together in a single clade.
Key words: Anacardiaceae, Burseraceae, matK, trnF, trnL