Systematic Implications of Pollen Morphology in Caryopteris (Labiatae)

Caryopteris, an Asian genus of 16 species, has greater pollen diversity than has been reported in any other genus of Labiatae. The pollen morphology of 15 species is documented here. Three pollen types are distinguished on the basis of exine structure and sculpturing: spinulose to spinose with slender, finely divided columellae (alternatively interpretable as an expanded tectum); verrucate with a well defined tectum and thick, sparsely branched columellae; and suprareticulate to microreticulate with moderately thick, sparsely branched columellae. Thirteen species are tri- colpate, Caryopteris divaricata is triporate, and C. nepalensis is 6-pantocolpate. Pollen morphology and correlated variation in floral and fruit morphology suggest that Caryopteris comprises three primary phenetic groups. However, two recent cladistic analyses (one based in part on the pollen features documented here) indicate that the genus is para- or polyphyletic and that only one of the three phenetic subgroups is clearly monophyletic. Recircumscription of the genus is recommended, but this should await completion of current studies that will facilitate its subdivision into monophyletic taxa.