Nectar features, diurnal and nocturnal pollinators, and male fitness in Qualea grandiflora (Vochysiaceae)

Abstract

Nectar production in flowers has been associated with pollination systems and seen as part of plant reproductive strategies. But other factors may have a role on nectar features and its efficacy as reward. We investigated pollination system of Qualea grandiflora, the most widespread woody species of Cerrado, the Neotropical savannas in Central Brazil, focusing on nectar features, their relationship with nocturnal and diurnal pollinators and how nectar affects male fitness, measured through pollen removal. Qualea grandiflora flowers during rainy season; anthesis starts at dusk, with a slightly sweet scent, pollen release and receptive stigma. Flowers remained opened until next evening and were visited and pollinated by a wide range of nocturnal and diurnal animals. Hawk moths were more frequent and responsible for most Q. grandiflora male fitness. Nectar was secreted during the night and early morning, with maximum accumulated volume up to 20.9 μl. Sugar concentration (23.12%) and amount (1.79 mg) remained constant during flower lifespan. No signals of active nectar resorption were observed. Nectar sugar composition was sucrose dominant during the night, and sucrose and hexose rich during the day. Standing crop measurements indicated an important proportion of nectar intake by flower visitors. Qualea grandiflora seemed to synchronize its floral and nectar features with hawk moths. However, nectar composition encompasses general preferences by both diurnal and nocturnal pollinators, assuring a mixed pollination system which seems well adapted to the species continental-scale distribution.