REVIEW PAPER Floral scents: their roles in nursery pollination mutualisms Martine Hossaert-McKey • Catherine Soler • Bertrand Schatz • Magali Proffit Received: 1 December 2009 / Accepted: 7 February 2010 / Published online: 5 March 2010 Ó Springer Basel AG 2010 Abstract Mutualisms are interspecies interactions in which each participant gains net benefits from interacting with its partner. In nursery pollination mutualisms, poll- inators reproduce within the inflorescence they pollinate. In these systems, each partner depends directly on the other for its reproduction. Therefore, the signal responsible for partner encounter is crucial in these horizontally trans- mitted mutualisms, in which the association between specific partners must be renewed at each generation. As in many other interspecies interactions, chemical signals are suspected to be important in the functioning of these mutualisms. We synthesized and compared the published data available on the role of floral scents in the functioning of the 16 known independently evolved nursery pollination mutualisms. So far, attraction of pollinators to their specific hosts has been investigated in only seven of these systems, and the majority of the studies have been conducted on one of them, fig/fig wasp interactions. While such unevenness of the information limits the potential for meta-analysis, some patterns emerge from this review concerning the role of flower volatiles in maintaining the specificity of polli- nator attraction, in signaling the appropriate phenological stage for pollinator visit, in attracting the pollinator toward the rewardless sex in dioecious plant species and in aiding the location and exploitation of resources by parasites and predators associated with these mutualisms. Finally, we highlight new perspectives on the evolution of signals in these diversified systems depending on the age and the degree of specificity of the interaction, and on the effect of phylogenetic inertia on the evolutionary dynamics of plant signals. Keywords Chemical mediation Á Specific pollination Á Pollination by deceit Á Community ecology Á Pollinator behavior Á Evolutionary ecology Introduction Mutualisms are cooperative interactions between species, in which each partner benefits from the association (Bronstein et al. 2006). In nursery pollination mutualisms, pollinators lay eggs within plant reproductive structures when pollinating flowers, using these structures of the host plant as their only breeding sites (Dufay ¨ and Anstett 2003). Among these mutualisms, the most diverse and well- known examples are the interactions between figs and fig wasps (Anstett et al. 1997; Cook and Rasplus 2003; Herre et al. 2008) and those between yuccas and yucca moths (Pellmyr 2003). However, in addition to these textbook examples, a handful of other nursery pollination mutual- isms have been described in greater or lesser detail (Dufay ¨ and Anstett 2003; Kawakita and Kato 2009). Nursery pollination mutualisms represent high taxonomic diversity of both plants and insects, and show independent and convergent evolution (Dufay ¨ and Anstett 2003). They share many properties in their ecological functioning. Moreover, they may use similar mechanisms to facilitate partner encounter. This is a crucial step in these horizontally transmitted mutualisms in which each partner depends directly on the other for its reproduction. Indeed, as in many other plant/pollinator interactions, flower scents— M. Hossaert-McKey (&) Á C. Soler Á B. Schatz Centre d’E ´ cologie Fonctionnelle et E ´ volutive (CEFE), UMR 5175 CNRS, 1919 route de Mende, 34293 Montpellier, France e-mail: martine.hossaert@cefe.cnrs.fr M. Proffit Chemical Ecology Group, Swedish University of Agricultural Sciences (SLU), SE-23053 Alnarp, Sweden Chemoecology (2010) 20:75–88 DOI 10.1007/s00049-010-0043-5 CHEMOECOLOGY