Estratégia reprodutiva de Cochlospermum orinocense (Kunth) Steud.: fenologia, biologia floral e sistema de cruzamento em uma espécie pioneira de florestas na Amazônia

Abstract

Cochlospermum orinocense (Kunth) Steud. is an arboreal species found in forest edges, canopy gaps and secondary forests. Phenology, floral biology and breeding system data was gathered at the edge of an 80 ha primary terra-firme Amazonian forest fragment in the Sao Luis Island, Maranhao state. Cochlospermum orinocense is a deciduous species which flower annually, showing intense and synchronized flowering early in the dry season. Its hermaphrodite and slightly zygomorphic flowers are arranged in terminal inflorescences and last only one day. Each ovary has on average 250 ovules and the androecium about 160 poricidal dehiscence anthers presenting 81.6% viable pollen and P/O ratios of 16,019.2. Anthesis is diurnal and the flowers are pollinated mainly by solitary bees of the species Centris spp. Cochlospermum orinocense is self-compatible (ISI = 0.98) with high reproductive efficacy (RE = 0.81) and reduced or null apomixis. Clustered distribution in deciduous trees together with intense and synchronized flowering in the dry season leads to highly efficient pollination. Fecundity is thus limited to resources constraints and not by pollen availability. Geitonogamy, the commonest form of endogamy, may assure the reproductive success of isolated individuals in the forest but leads to endogamic depression. The high density clustering often found in this species encourages allogamy and may allow high reproductive efficiency and higher fecundity as endogamic depression is minimized.