Format: ORAL

Paulo E. Oliveira1, Renata T. Telles2, Joo C. Cardoso3, Ebenezer B. Rodrigues1, Christiano P. Coelho4, Helder N. Consolaro5

1 Universidade Federal de Uberlândia, Uberlândia, Brazil 2 Universidade Estadual de Campinas, Campinas, Brazil 3 Universidade Federal de Ouro Preto, Ouro Preto, Brazil 4 Universidade Federal de Jatai, Jataí, Brazil 5 Universidade Federal de Catalão, Catalão, Brazil

The Rubiaceae is a widely distributed, megadiverse angiosperm family. Distyly is the prevalent floral system in many Rubiaceae, especially in the Brazilian Cerrado and other tropical environments. Besides two floral morphs with reciprocal stigma and stamens heights, distyly is associated with a heteromorphic incompatibility system and other ancillary morphological traits. Since the majority of Rubiaceae depends on precise biotic pollination services for their reproductive success, distyly is vital for their persistence. Nevertheless, morphological changes followed by the loss of floral polymorphism are common, leading to anomalous species or populations displaying homostyly, monomorphism or even dioecy. These reproductive transitions have occurred repeatedly in the Psychotrieae alliance, which includes the most speciose distylous genera, Palicourea and Psychotria. Anomalous distyly cases do not show any clear phylogenetic clustering, but seem to be associated with anthropized/disturbed or island environments, and inefficient pollination. As in other distylous groups, these changes have been explained by sudden mutation events within a supergene model, which include both morphological and self-incompatibility alleles. However, community-wide approaches have shown that distylous Rubiaceae lack precise reciprocity in the height of their sexual organs, often displaying higher inaccuracies either in low or higher organs. These changes seem to be linked to reduced floral integration, possibly under pressure from the loss of precise pollination, which seems to be required for efficient distyly functioning. The losses of ancillary features and reciprocity are often associated with less strict self-incompatibility. We suggest here that the reduction of floral integration and reciprocity, besides other ancillary features associated with distyly, may be intermediate transition stages. In more advanced stages, these changes may lead to a complete breakdown of the system. Such trends can be used as indicators of environmental pressures on distyly functioning. (We thank CAPES, CNPq, and FAPEMIG for funding)