Pollen morphological variation in Vanguerieae (Ixoroideae Rubiaceae)

The Vanguerieae is a large tribe of the subfamily Ixoroideae (Rubiaceae) an d consists of about 500 species in 27 genera. This study gives a detailed p ollen morphological description of 30 species from 16 genera, based on ligh t microscopy and scanning electron microscopy. The Vanguerieae are consider ed to be stenopalynous, although there is some evidence to question this. F irst, there is a difference in sexine types that clearly defines kectia and Psydrax (both reticulate): and Canthium and Vanguerieae (both perforate wi th Very small perforations) from the other Vanguerieae investigated. Second ; pollen grains corroborate the subgeneric delimitations of Canthium sensu Bridson. Pollen morphologically the tribe is characterised by (1) the shape of the ectoapertures which is intermediate between a colpus and a porus, a nd (2) the presence of a costa oriented perpendicular to the ectoaperture a nd has a form which is correlated with the shape of the costa.