Palynology of South Pacific Cyrtandra (Gesneriaceae) with notes on some Hawaiian taxa

Pollen of 34 accessions (23 species, one putative hybrid) of South Pacific and Hawaiian Cyrtandra was investigated by SEM. Most pollen grains are isopolar, 3-colpate, spheroidal in equatorial view, and circular in polar view. Only C. kamooloaensis (Hawaii) exhibits suboblate pollen grains. Average equatorial diameters range from 9 to 16mum. In general, colpi are long and tapering. Colpus membranes show granular elements which decrease in size from the equatorial to the polar regions. Most taxa exhibit a microreticulate mesocolpial exine pattern, in some cases with a tendency to reticulate or fossulate pattern. Lumina size varies within the mesocolpial region of single grains, average lumina diameter is either similar throughout grains or decreases towards the colpial borders or the apocolpial region. C. kamooloaensis exhibits the smallest lumina reported for Hawaiian Cyrtandra so far. In some species, distinct free-standing columellae are present. Except for a fine granular ornamentation of shallow grooves on the muri of the Samoan C. richii supratectal elements are lacking. Pollen of South Pacific Cyrtandra does not provide characters directly suitable for generic subdivisions. There is no obvious correlation between morphologically defined species groups and exine types, but some evidence for parallel evolution of these types. Nearly related taxa (e.g., the C. cymosa group of Gillett 1973) show considerable palynological differences. Variation within some currently accepted species is more prominent than between taxa clearly belonging to different evolutionary lines. This could reflect deficiencies in species delimitation.