5, df = 1, P = 0.001), (E)-cinnamyl alcohol (χ2 = 9.3, df = 1, P = 0.002) and (E)-cinnamaldehyde (χ2 = 16.6, df = 1, P < 0.0001) over control wicks with paraffin only

( Fig. 5). Post hoc tests selleck products showed no differences of ant preferences between (E)-cinnamaldehyde, (E)-cinnamyl alcohol and the mixture of the compounds ( Fig. 5). The number of ants attending wicks containing the mixture of synthetic compounds (χ2 = 52.6, df = 1, P < 0.0001), (E)-cinnamyl alcohol (χ2 = 66.0, df = 1, P < 0.0001) and (E)-cinnamaldehyde (χ2 = 79.5, df = 1, P < 0.0001) was higher than the number in control wicks (Fig. 2S). No preference for 4-oxoisophorone was observed ( Fig. 5). Supplementary Fig. II.  Total number of ant visits in the two-choice Etoposide supplier trials involving the most abundant volatile compounds in the scent of Cytinus flowers: (E)-cinnamaldehyde, (E)-cinnamyl alcohol, 4-oxoisophorone and the synthetic blend of these three compounds. Symbols indicate significant differences: ***P < 0.0001, n.s., nonsignificant differences (P > 0.05). Our study has provided compelling evidence that ants are strongly attracted by Cytinus floral scent. Chemical cues

alone were sufficient to elicit conspicuous positive responses in several ant species that effectively pollinate Cytinus flowers. Ants have been traditionally considered nectar thieves, and even some flowers have been shown to emit volatiles (allomones) repellent for ants (see references in the Introduction). However, we have shown that when plants benefit from ant visitation, floral volatiles can function as synomones with an important role in ant attraction. Since ants that function as efficient pollinators are

attracted by Cytinus floral scent, floral volatiles clearly provide an advantage to the plant and may help to maintain a mutualistic relationship with ants, as discussed below. Any cue improving the net benefit for each partner in a plant–animal mutualism may evolve into a communication signal (Blatrix and Mayer, 2010). Visual and olfactory signals that help guide insects to the flowers and favour pollination are consequently expected to play an important role in the ecology and evolutionary diversification of plant-pollinator interactions (Raguso, 2001, Fenster et al., 2004, Peakall et al., 2010, Schiestl, 2010 and Schäffler et al., 2012). Cytinus has brightly coloured flowers Plasmin that may have evolved to increase their visual attraction to pollinators. However, the inflorescences appear at ground level under the canopy of their host plant, and sometimes are even found hidden in leaf litter. This could reduce their visual conspicuousness and hence could limit the importance of visual cues for insect attractiveness. Since Cytinus depends on pollinators to set seed ( de Vega et al., 2009), we suggest that the evolution of olfactory cues may have played an important role in the attraction of ground-dwelling insect pollinators.