Pollinator and Herbivore Attraction to Cucurbita Floral Volatiles

Abstract

Mutualists and antagonists may place conflicting selection pressures on plant traits. For example, the evolution of floral traits is typically studied in the context of attracting pollinators, but traits may incur fitness costs if they are also attractive to antagonists. Striped cucumber beetles (Acalymma vittatum) feed on cucurbits and are attracted to several volatiles emitted by Cucurbita blossoms. However, the effect of these volatiles on pollinator attraction is unknown. Our goal was to determine whether pollinators were attracted to the same or different floral volatiles as herbivorous cucumber beetles. We tested three volatiles previously found to attract cucumber beetles in a factorial design to determine attraction of squash bees (Peponapis pruinosa), the specialist pollinators of cucurbita species, as well as the specialist herbivore A. vittatum. We found that 1,2,4-trimethoxybenzene was attractive to both the pollinator and the herbivore, indole was attractive only to the herbivore, and (E)-cinnamaldehyde was attractive only to the pollinator. There were no interactions among volatiles on attraction of squash bees or cucumber beetles. Our results suggest that reduced indole emission could benefit plants by reducing herbivore attraction without loss of pollination, and that 1,2,4-trimethoxybenzene might be under conflicting selection pressure from mutualists and antagonists. By examining the attraction of both mutualists and antagonists to Cucurbita floral volatiles, we have demonstrated the potential for some compounds to influence only one type of interaction, while others may affect both interactions and possibly result in tradeoffs. These results shed light on the potential evolution of fragrance in native Cucurbita, and may have consequences for yield in agricultural settings.

Diversity of volatile organic compound emissions from flowering and vegetative branches of Yeheb, Cordeauxia edulis (Caesalpiniaceae), a threatened evergreen desert shrub

“…However, we are not sure whether an increase in isoprene and other VOCs from FBs of Yeheb was from the fl owers or leaves on fl owering branches, as our sampling system did not allow the sampling of fl owers without the leaves in the same branch. The strong association of monoterpene emission with FBs observed with PCA analysis indicates that the major part of the volatile blend emitted from fl owers was monoterpenes, suggesting that this is important for attracting pollinators, as recently reported by Andrew et al [8] and Raguso. [42] The higher amount of volatiles identifi ed from FBs than VBs of Yeheb may indicate that part of the pollinator-attracting VOC emissions could be even produced by FB foliage to improve pollinator success.…”

“…Among the compounds emitted in higher concentrations by FBs, β-pinene, (E)-β-ocimene, linalool, toluene, benzaldehyde and indole have been reported as part of the fl oral scent. [8] Moreover, (E)-β-ionone was indicated by Flamini et al [39] as a typical compound in the fl oral scent of leguminous plants. This higher emission of volatiles from FBs is in agreement with the previous fi ndings of Hansen and Seufert, [40] who found 7.8-fold higher total emissions of terpenoids from Citrus sinensis (L.) branches with fl owers than from branches without fl owers.…”

“…The biological and ecological functions of volatile terpenes include direct and indirect protection of plants against insect herbivores [2] and microbial pathogens, [7] attraction of pollinators [8] and as mediating agents of plant-plant competition. [9] Additionally, VOCs play a major role in plant-plant signalling by inducing defence responses in neighbouring plants, act in intraplant signalling, [10] and help plants to communicate with organisms of higher trophic levels.…”

Volatiles from <i>Prunus persica</i> Flowers and Their Correlation with Flower-Visiting Insect Community in Wanbailin Ecological Garden, China

“…The evolution of floral traits in the context of attracting mutualist or antagonist pollinators may place conflicting selection pressures on plant traits, and the effect of these volatiles on pollinator attraction is indeterminate [22]. Many flowers produce volatiles at times when pollinators are most active; VOCs such as a kind of muurolene are characteristics of the syconium pollen receptive diurnal phase, and may attract the diurnally-active pollinating wasps [23].…”

Beetle visitations, and associations with quantitative variation of attractants in floral odors of Homalomena propinqua (Araceae)

“…In contrast, C. schawalleri appears to recognize the presence of H. propinqua by olfactory cues only, and the other floral traits, such as visual cues or heat, may be less important. Veratrole, which was attractive to C. schawalleri, is reported to be an attractant of anthophagous chrysomelid beetles (Metcalf and Lampman 1991;Ventura et al 2000;Andrews et al 2007). Veratrole is an important cue for C. schawalleri.…”