Studies on the reproductive biology of Melastomataceae in "cerrado" vegetation

Controlled pollinations and observations of pollen tube growth, pollen fertility and cytological data were studied in 11 species of Melastomataceae growing in "cerrado" in SE Brazil. Seven species produced apomictic fruits with viable seeds. Four species were not apomictic, with two self-incompatible (gametophytic ST) and two self-compatible, one showing spontaneous self-pollination. The apomictic species had lower pollen fertility than sexual ones -although in some cases differences were not significant -showing that low pollen fertility may be a useful indicator of apomixis if analysed using careful sampling supplemented by emasculation experiments. The apomictic species also showed meiotic irregularities, probably related to hybridization, polyploidy and the cause of low pollen fertility. Apomixis in this group probably is more associated with taxonomy and phylogeny than habitat or habit, since 85% of the apomictic species reported in the literature belong to the tribe Miconieae and occur in a wide range of vegetation types and have diverse habits. This suggests the existence of very extensive apomictic complexes comparable to those reported in mainly temperate genera of Asteraceae and Rosacene.