Covariation and phenotypic integration in chemical communication displays: biosynthetic constraints and eco‐evolutionary implications

Abstract

Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking. We assessed the phenotypic integration of CCDs in a meta-analysis to characterize patterns of covariation in CCDs and identified functional or biosynthetically constrained modules. Poorly integrated plant CCDs (i.e. low covariation between scent compounds) support the notion that plants often utilize one or few key compounds to repel antagonists or to attract pollinators and enemies of herbivores. Animal CCDs (mostly insect pheromones) were usually more integrated than those of plants (i.e. stronger covariation), suggesting that animals communicate via fixed proportions among compounds. Both plant and animal CCDs were composed of modules, which are groups of strongly covarying compounds. Biosynthetic similarity of compounds revealed biosynthetic constraints in the covariation patterns of plant CCDs. We provide a novel perspective on chemical communication and a basis for future investigations on structural properties of CCDs. This will facilitate identifying modules and biosynthetic constraints that may affect the outcome of selection and thus provide a predictive framework for evolutionary trajectories of CCDs in plants and animals.

Nectar‐inhabiting microorganisms influence nectar volatile composition and attractiveness to a generalist pollinator

“…). A recent meta‐analysis indicated that floral volatile profiles are, on average, the most variable of all plant or animal volatile blends examined (Junker et al ., ). Our data suggest that nectar microbes can contribute to this variability.…”

Exotic flower visitors exploit large floral trait spaces resulting in asymmetric resource partitioning with native visitors

“…Usually, qualitative intraspecific variation is much lower than interspecific variation (Junker et al. ; Kuppler et al., ) because each plant species adds new compounds to communities (Junker, ). Accordingly, in our samples most substances were emitted by only one or a few plant species, resulting in a zero‐inflated matrix and thus preventing a meaningful analysis; therefore, we grouped the compounds according to their biosynthetic origin and their functional groups: aliphatics (A), aromatics (AR), C5‐branched pathway (C5), irregular terpenes (IT), monoterpenes (MT), sesquiterpenes (ST) (Table S4, S5).…”

Introduction to a special feature issue – New insights into plant volatiles

“…In a compilation of a large number of studies Junker et al . (in this issue, pp. 739–749) took a pioneering step to approach the diversity of VOCs as a trait that can be used for comparative studies in ecology and evolution.…”

“…One of the major conclusions of this study by Junker et al , was that we are, at best, at the beginning of understanding how chemical information is encoded, although we have a large number of studies that seem to be able to assign a particular function to a particular VOC or group of VOCs. The multifunctionality that seems characteristic to most secondary metabolites, and the likely context dependency of each compound in a particular chemical and ecological environment, makes the identification of common principles of chemical information difficult.…”

“…They are important in endogenous signaling where they mediate information on a cellular level, affect interactions between the plant and a multitude of organisms and, because of the massiveness of some of the emissions, such as monoterpenes and isoprenes, can affect atmospheric chemistry. While the discovery of new functions for VOCs will continue, the important foci for the future lie in furthering of our understanding of the biosynthesis, regulation, transport and perception of plant VOCs (Pichersky & Raguso; Ameye et al .), as well as the identification of basic patterns that help decode this chemical language (Junker et al ,) and help understand the information noise that derives from compromising biotic and abiotic factors. In the end we may come a bit closer to understanding how important chemical communication and VOCs are in mediating interactions among the organisms comprising a ‘tangled bank’ and how these chemical languages ‘have been and are being evolved’.…”