Pollen morphology in the genus Bonamia Thouars (Convolvulaceae) and its taxonomic significance

Abstract

Bonamia Thouars (Convolvulaceae) comprises about 60 species, widely distributed through North and South America, Africa, Madagascar, South and Southeast Asia, and Australia. Bonamia is variable, possessing at least two different pollen types, and its current circumscription is controversial. From recent phylogenetic studies in the family, it is established that Bonamia is paraphyletic. Ongoing taxonomic, morphological and molecular phylogenetic studies for the clarification of the real circumscription of Bonamia and its infrageneric relationships, have involved also the pollen analyses of 36 species of Bonamia. The pollen grains were acetolyzed and microphotographed under light microscopy and analyses under Scanning Electron Microscopy. The results increase with descriptions of pollen for taxa never described, as well as species recently described for science and have demonstrated that the pollen grains of all species analyzed are monads, with isopolar, 3-colpate (32 spp.) and 12–32-pantocolpate (4 spp.) since only two pollen types and some variations were cited for the genus we present here five pollen types divided by sections. The exine presented variable ornamentation, with microspines, granules or verrucae and formation of perforations, microreticula and reticula. The palynological features allowed the classification into two major groups: (1) with polar pollen grains and 3-colpate apertures and; (2) with apolar pollen grains with 12–32-pantocolpate. We conclude that Bonamia, in its current circumscription, is euripalynous mainly in what concerns polarity and aperture type.