Pollination biology of melittophilous legume tree species in the Atlantic Forest in Southeast Brazil

ABSTRACT This study describes the floral phenology and morphology, reproductive biology and pollinators for eight legume tree species, Schizolobium parahyba, Senna macranthera, and Senna multijuga (Caesalpinioideae), as well as Andira fraxinifolia, Lonchocarpus cultratus, Pterocarpus violaceus, Swartzia oblata, and S. simplex (Papilionoideae), in the Atlantic Forest in Southeast Brazil. All the studied species showed an annual flowering pattern, and almost all are of the cornucopia-flowering type, with the only exception being Swartzia oblata, which was of the steady-state type. In general, the legume flowers studied are conspicuous, mostly medium-sized, and offer nectar and/or pollen as a resource. Self-incompatibility associated with the production of many flowers and consequent pollen discounting due to self-pollination may contribute to low fruit set of these species in natural conditions. Fifty bee species were recorded visiting the flowers, with medium to large-sized Apidae bees, such as Bombus morio, and species of Xylocopa, Centridini and Euglossina, which were among the most frequent visitors and major pollinators. These bees showed high floral constancy, thus they are significant to the reproductive success of these tree species. This study provides information regarding the interactions between bees and these eight legume species and evaluates the importance of pollinators for their sexual reproduction.

【摘要】 本研究针对巴西东南部大西洋森林中的8种豆科乔木，系统探究了其开花物候（floral phenology）与形态特征、生殖生物学（reproductive biology）特性及其传粉媒介（pollinators）。涵盖的物种包括云实亚科（Caesalpinioideae）的*Schizolobium parahyba*、*Senna macranthera*与*Senna multijuga*，以及蝶形花亚科（Papilionoideae）的*Andira fraxinifolia*、*Lonchocarpus cultratus*、*Pterocarpus violaceus*、*Swartzia oblata*及*S. simplex*。所有供试物种均呈现年度开花模式（annual flowering pattern），且绝大多数为丰花型（cornucopia-flowering）开花类型，仅*Swartzia oblata*为稳态开花型（steady-state）。总体而言，本次研究的豆科花朵醒目显著，多为中型尺寸，可为传粉者提供花蜜与/或花粉作为报酬。自交不亲和性（self-incompatibility）伴随大量花朵产生，加之自花授粉引发的花粉折扣（pollen discounting）效应，可能是导致这些物种在自然条件下坐果率（fruit set）偏低的重要原因之一。本研究共记录到50种访花蜂类，其中体型中等至大型的蜜蜂科（Apidae）昆虫最为常见，包括*Bombus morio*、木蜂属（Xylocopa）物种、切叶蜂族（Centridini）类群以及Euglossina族昆虫，它们既是最频繁的访花者，也是主要的传粉者。这类蜂类具有较高的花忠实性（floral constancy），因此对这些乔木物种的生殖成功具有关键作用。本研究阐明了蜂类与这8种豆科植物之间的种间互作关系，并评估了传粉媒介对其有性生殖的重要性。