A dual function for 4-methoxybenzaldehyde in Petasites fragrans? Pollinator-attractant and ant-repellent

Abstract

Ant-repellent floral volatiles offer one method through which plants can mediate the detrimental effects of ants on flowers. Although the repellence itself is well documented, the volatiles involved are less well explored. Here, we investigated the floral bouquet of ant-repellent male flowers of Petasites fragrans, identifying 4-methoxybenzaldehyde as the main component. 4-methoxybenzaldehyde significantly repelled ants when presented in isolation in an olfactometer and thus is the likely source of the repellent effect. As 4-methoxybenzaldehyde has previously been shown to attract pollinators, it may therefore have a dual function in P. fragrans, pollinator-attractant and ant-repellent. Additionally, 4-methoxybenzaldehyde is particularly interesting as an ant-repellent as it has been observed in the bouquets of other plant species with specific ant interactions.

The defensive function of a pollinator‐attracting floral volatile

“…A similar dual function has been suggested earlier by Galen et al () who provided evidence that 2‐phenylethanol may deter ants in Polemonium viscosum without deterring pollinators at the same time. Furthermore, Pattrick et al () showed that 4‐methoxybenzaldehyde respells ants in the Winter Heliotrope Petasites fragrans and discusses a general ant repellent effect of this compound, while the same compound has been found to attract pollinators in the thistle Cirsium arvense (Theis, ). However, even within a plant species, a single compound has been shown to have a dual function recently.…”

“…Junker, Daehler, Dötterl, Keller, and Blüthgen () and Junker, Gershenzon, and Unsicker () showed attractive and repellent functions of natural floral scents for a variety of flower visitors in the field using olfactometer trials. Recent literature even hypothesized that a single scent compound may have a dual function (in regard to the pollinator–florivore trade‐off) in the same plant species (Pattrick, Shepherd, Hoppitt, Plowman, & Willmer, ), namely attracting pollinators and deter antagonists. Floral visitors, either mutualistic or antagonistic, may have evolved a tolerance to deterrent and toxic compounds present in floral scents, which could lead to variable responses of different insect visitors (Farré‐Armengol, Filella, Llusia, & Peñuelas, ; Junker & Blüthgen, ) to a single volatile compound.…”

Comparative effects of pollen limitation, floral traits and pollinators on reproductive success of Hedysarum scoparium Fisch. et Mey. in different habitats

“…Our results indicate that pollen release by H. scoparium occurred from 09:00 to 15:00, which corresponded to the most critical period for pollination, and furthermore, coincided with peak visits from A. mellifera . Previous reviews indicated that honeybee has an outstanding role in many of the crops’ pollination, but Apis mellifera sometimes was not a very successful pollinator [ 36 , 37 ]. Ryan and David suggested that the convergent evolution of floral traits with the traits of their dominant pollinators is widespread in plants and constitutes one of the most visual demonstrations of natural selection [ 38 ].…”

Chemistry, biosynthesis and biology of floral volatiles: roles in pollination and other functions

“…However, linalool ( 60 and/or 61 ) was only repellent when offering the compound in concentrations higher than released from the flowers, suggesting that other compounds are also involved in repelling ants from the flowers. 347 Other flower volatiles known to be repellent to ants are p -anisaldehyde ( 111 ) from Petasites fragrans flowers 349 and 2-phenylethanol ( 84 ) from flowers of the alpine skypilot Polemonium viscosum . 350 In the latter species, the flowers are polymorphic in the amount of 84 emitted.…”