Morfologia da flor de Ludwigia nervosa (Poir.) H. Hara (Onagraceae) vs. abelhas visitantes, há alguma relação?

Abstract

This study investigated the floral and reproductive biology, phenology and diversity of bees visiting Ludwigia nervosa (Poir.) H. Hara. The research was conducted in a forest fragment in the city of Ivinhema, Mato Grosso do Sul, Brazil. For this, the floral phases, floral visitors and the floral resources available to these insects were all described. The stigma receptivity, pollen viability, flowering and fruiting peaks were investigated. Reproductive tests (treatments) were performed through manual selfpollination, spontaneous self-pollination, geitonogamy, xenogamy, apomixis and natural pollination. After the fruits formation, they were counted, measured and their seeds were placed in a plastic box in order to germinate. Ludwigia nervosa blossomed and had a prolonged flowering period during the year, with a peak activity in the rainy season. Flowers lasted a whole day, providing floral resources like pollen and nectar. The stigma receptivity was noticed in the pre-anteroom phase at 5 am, the period in which pollen viability was higher (82.87%), and decreased until senescence (21.38%), that could be noticed after 13 pm. The visiting species were: Exomalopsis, Xylocopa, Megachile and Apis mellifera, including effective pollinators such as Megachile species and occasional species such as Exomalopsis, Xylocopa and Apis mellifera. Typical morphological characteristics that attend the melitophilia pollination type syndrome were predominant, however, other types of syndromes with a less important contribution in pollination processes were also observed. In reproductive tests, there were fruits formation only by xenogamic pollen. Therefore, the species pollinators are proven efficient since a greater number of fruits (76%) and germination processes (78%) were verified in tests under natural condition (natural pollination). As a result, the reproductive success of Ludwigia nervosa is closely related to the foraging behavior of effective pollinators that promote efficient pollen transport.