Temporal variation of flower scent in Silene otites (Caryophyllaceae): a species with a mixed pollination system STEFAN DÖTTERL 1 , KATRIN JAHREIß 1 , UMMA SALMA JHUMUR 2 and ANDREAS JÜRGENS 3 * 1 Department of Plant Systematics, University of Bayreuth, D-95440 Bayreuth, Germany 2 Department of Biology, University of Konstanz, D-78457 Konstanz, Germany 3 School of Life Sciences, University of KwaZulu-Natal, P. Bag X01 Scottsville, Pietermaritzburg 3209, South Africa Received 27 July 2011; revised 12 January 2012; accepted for publication 28 January 2012 Floral scent composition and emission are often related to olfactory abilities, preferences and activity times of pollinating agents. However, most studies have focused on species with one pollinator type, and little is known about species with mixed pollination systems. We investigated the temporal variation in flower visitor activity and flower scent emission of Silene otites (Caryophyllaceae), a species regarded as being nocturnal and pollinated by moths and mosquitoes. We found, however, that S. otites is not only visited at night by moths and mosquitoes, but also by a wide range of day-active insects. Furthermore, both the intensity and composition of floral scent change during the course of the day. Total scent emission reached its maximum in the early hours of the night when compounds known to be attractants for moths and/or mosquitoes, such as lilac aldehyde, benzaldehyde, pheny- lacetaldehyde and 2-phenylethanol, dominated the scent. However, although less intensive, emission continued during the day. In the early morning, a-pinene, hotrienol, 2-phenylethanol and d-3-carene were the dominant scent compounds. (E)-b-Ocimene, hotrienol and benzyl alcohol contributed proportions of at least 10% before midday when flies, such as syrphids, were abundant flower visitors, whereas linalool and hotrienol contributed to the scent with at least 10% each in the afternoon when bees also contributed to flower visits. We conclude that, in S. otites, the changing emission patterns are ‘in tune’ with the olfactory abilities, preferences and activity times of its day- and night-active potentially pollinating flower visitors. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 447–460. ADDITIONAL KEYWORDS: diel odour patterns – diurnal – dynamic headspace – floral volatile composition – flower visitors – GC-MS – nectar-drinking mosquitoes – nocturnal – pollinator attraction. INTRODUCTION The complex features of angiosperm flowers are gen- erally interpreted as adaptations for attracting and exploiting certain types of pollinator and for exclud- ing other types of flower visitor (Fenster et al., 2004). Floral odours are important for chemical communica- tion between plants and their day- and night-active pollinators (Pellmyr & Thien, 1986; Dobson, 2006; Knudsen et al., 2006) and may affect pollinator choices and behaviour and, in turn, plant reproduc- tion (Pellmyr, 1986) in two ways. First, there is evi- dence that the time of floral scent emission is significant for the interaction with certain groups of pollinators (Dobson, 2006; Knudsen et al., 2006), e.g. nocturnal scent maxima corresponding to the attraction of night-active pollinators, and, second, similarities in the composition of floral volatiles have been found in plants visited by the same pollinator type, for example, bats (Knudsen & Tollsten, 1995; Bestmann, Winkler & von Helversen, 1997), beetles (Thien, Heimermann & Holman, 1975; Yasukawa *Corresponding author. E-mail: juergensa@ukzn.ac.za Botanical Journal of the Linnean Society, 2012, 169, 447–460. With 2 figures © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169, 447–460 447 Downloaded from https://academic.oup.com/botlinnean/article/169/3/447/2416102 by guest on 11 September 2022