The evolution of floral scent and insect chemical communication

Abstract

Plants have evolved a range of strategies to manipulate the behaviour of their insect partners. One powerful strategy is to produce signals that already have a role in the animalsÕ own communication systems. To investigate to what extent the evolution of floral scents is correlated with chemical communication in insects, I analyse the occurrence, commonness, and evolutionary patterns of the 71 most common ÔfloralÕ volatile organic compounds (VOCs) in 96 plant families and 87 insect families. I found an overlap of 87% in VOCs produced by plants and insects. ÔFloralÕ monoterpenes showed strong positive correlation in commonness between plants (both gymnosperms and angiosperms) and herbivores, whereas the commonness of ÔfloralÕ aromatics was positively correlated between angiosperms and both pollinators and herbivores. According to a multivariate regression analysis the commonness of ÔfloralÕ aromatics was best explained by their commonness in pollinators, whereas monoterpenes were best explained by herbivores. Among pollinator orders, aromatics were significantly more common in Lepidoptera than in Hymenoptera, whereas monoterpenes showed no difference among the two orders. Collectively, these patterns suggest that plants and insects converge in overall patterns of volatile production, both for attraction and defence. Monoterpenes seem to have evolved primarily for defence under selection by herbivores, whereas aromatics evolved signalling functions in angiosperms, primarily for pollinator attraction.

Identification and Field Evaluation of Attractants for the Cranberry Weevil, Anthonomus musculus Say

“…Although the reason for this difference remains unknown, it is possible that host plant might affect the production of geraniol in male A. musculus or its emission after herbivore feeding damage. Geraniol is a monoterpenoid alcohol commonly emitted from plants, particularly flowers (Schiestl, 2010), that is induced by herbivore feeding (Han and Chen, 2002), and with known activity on insects, including mosquitoes (e.g., Qualls and Xue 2009) and bees (e.g., Williams et al, 1981). Besides Anthonomus spp., it is a component of the honey bee pheromone (Boch, 1962;Pickett et al, 1980).…”

The origin and dynamic evolution of chemical information transfer

“…Schiestl [32] proposed that the chemical similarity of floral and insect aromatics is explicable by plants exploiting pre-existing biases of their pollinators that have been formed in the context of their intraspecific communication. However, this hypothesis should be tested against the alternative one that the protective functions of chemicals provide a common starting point for the evolution of communication in both plants and insects, since a number of aromatics are known for their antibactericidal, antifungal and nematocidal properties (e.g.…”

“…Functional shifts (exaptations) can include a major switch from unavoidable metabolic byproducts to attractants [14,30], minor modification from defence to alarm or a strong functional change from a defensive agent to an attractive substance as has been suggested for floral scents [31,32]. For example, resin excreted by blossom glands in the flowers of Dalechampia vines is collected by pollinating bees for use in nest construction [33].…”

Natural selection on floral volatile production inPenstemon digitalis: Highlighting the role of linalool

“…Scents are an important signal in plant-insect communication and therefore are expected to be under pollinator and antagonist-mediated selection. 2,3 Animalmediated selection on scent is predicted to be balancing due to conflicting selection pressures, if scents attract both mutualists and antagonists 4 but directional if a scent simultaneously attracts pollinators and repels enemies. 5 Of course, scent blends are generally composed of many volatiles and, thus, it is possible that different components of the blend will be under different forms of selection.…”