WIESE, ANNA K.* and L. ALAN PRATHER. Herbarium and Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI, 48824-1312. - Phylogenetic relationships in Cantua (Polemoniaceae): Inferences from cpDNA sequences, nrDNA ITS sequences, and pollen morphology.
Cantua is a small but complex genus in the Polemoniaceae
subfamily Cobaeoideae. The species have Andean distributions, and are
characterized by their shrubby or diminutively arborescent habits,
dimorphic shoots, and pantoporate pollen. Comparative gene sequencing
of the species has been undertaken for three regions of the
chloroplast genome (trnT - trnL 5' and trnL 3' -
trnF spacer regions, and partial ndhF coding region) and
the internal transcribed spacer region of nuclear ribosomal DNA to
help elucidate relationships within the genus and among members of the
subfamily Cobaeoideae. In a recent classification, the genus
Huthia was subsumed in Cantua, but no phylogenetic data
have been applied to this problem. Our phylogeny suggests that
Cantua is paraphyletic to the former genus Huthia, and
that C. (Huthia) coerulea is sister to C. quercifolia.
This result is consistent with the recent nomenclatural changes. A
preliminary study of the pollen morphology using scanning electron and
light microscopy corroborate the molecular results. Among
Cantua species, C. quercifolia and C. coerulea
share the pollen synapomorphy of irregularly spaced verrucae on their
areolate semitectate sexine.
Key words: Cantua, Huthia, Polemoniaceae