Nectar production in the pollen flower of Anemone nemorosa in comparison with other Ranunculaceae and Magnolia (Magnolia
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ORIGINAL ARTICLE
Nectar production in the pollen flower of Anemone nemorosa in comparison with other Ranunculaceae and Magnolia (Magnoliaceae) Claudia Erbar & Peter Leins
Received: 5 December 2012 / Accepted: 27 February 2013 # Gesellschaft für Biologische Systematik 2013
Abstract The observation that the flowers of Anemone nemorosa offer nectar to pollinating bee-flies (Bombylius major) prompted this investigation into the site of nectar secretion and nectary tissue. To allow comparison on a broader basis, other nectar-secreting pollen flowers of the Ranunculaceae and Magnolia (Magnoliaceae) were included in the analysis. The contradictory information available on the function of the mouthparts of bee-flies during nectar and pollen feeding motivated us to investigate the proboscis structure in detail by SEM. Our investigations in Anemone nemorosa proved, for the first time, nectar secretion in the genus Anemone s.s. (i.e. other than the Pulsatilla group) and in addition, within the family, a new type of a carpellary nectary. The latter is an epithelial nectary involving the whole epidermis of the ovarian part of the carpel. The nectary of Anemone nemorosa resembles that of Magnolia (e.g. M. stellata), which we re-investigated. In both Anemone nemorosa and Magnolia stellata, nectar production is limited mainly to the female phase of the proterogynous flower. In this way, the attractiveness of the flower is also assured in the non-pollen presenting phase. Especially in Magnolia, with its numerous carpels arranged on a cone-like receptacle, the economic disadvantage of a choricarpous- compared to a coenocarpous-gynoecium is compensated for by nectar secretion by each carpel. When licking up the nectar droplets from the carpel surfaces, contact of the insect's body with each stigma may be achieved.
C. Erbar (*) : P. Leins COS, Biodiversity and Plant Systematics, Universität Heidelberg, Im Neuenheimer Feld 345, Heidelberg, Germany e-mail: [email protected]
Keywords Nectaries . Anemone nemorosa . Clematis . Caltha . Pulsatilla . Ranunculus . Ranunculaceae . Magnolia stellata . Magnoliaceae . Proboscis of Bombylius major
Introduction In April 2010, in a beech forest near Heidelberg (Reilingen), we observed bee-flies, Bombylius major, visiting flowers of the wood anemone, Anemone nemorosa (Ranunculaceae). This was not a singular event; several individuals of Bombylius visited eagerly different flowers of the population of Anemone nemorosa. In between, Bombylius visited Vinca minor (Apocynaceae), where the insect is rewarded by copious nectar. The long mouthparts of bee-flies reach deep into the corolla tube when collecting nectar. But what is the reward in the Anemone flower? We never expected a bee-fly on Anemone, because Anemone is thought to be a true pollen flower and, at first sight, the mouthparts of Bombylius do not seem well suited to true pollen flowers. Small beetles, flies and bees are often recorded as visitors of Anemone nemorosa (e.g. Knuth 1898; Hegi 1912; Proctor et al. 1996). We ne
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