Reproductive biology of Caesalpinia calycina and C-pluviosa (Leguminosae) of the caatinga of north-eastern Brazil

The pollination biology, breeding system and fruiting success of Caesalpini a calycina and C. pluviosa var. sanfranciscana were studied in caatinga veg etation in Bahia, NE Brazil. The principal pollinators for both species wer e carpenter bees. Caesalpinia calycina is andromonoecious but in C. pluvios a all flowers are hermaphrodite. In C. calycina all selfed flowers were abs cised within 72 h despite rapid self-pollen tube growth to the ovary and ov ule penetration. Prevention of selfing therefore seems to be controlled by a post-zygotic mechanism. Both species had very low fruit-set and it is sug gested that this is at least in part due to geitonogamous pollinations with ovule penetration by self pollen tubes.