Floral Scent Contributes to Interaction Specificity in Coevolving Plants and Their Insect Pollinators

Abstract

Chemical defenses, repellents, and attractants are important shapers of species interactions. Chemical attractants could contribute to the divergence of coevolving plant-insect interactions, if pollinators are especially responsive to signals from the local plant species. We experimentally investigated patterns of daily floral scent production in three Lithophragma species (Saxifragaceae) that are geographically isolated and tested how scent divergence affects attraction of their major pollinator-the floral parasitic moth Greya politella (Prodoxidae). These moths oviposit through the corolla while simultaneously pollinating the flower with pollen adhering to the abdomen. The complex and species-specific floral scent profiles were emitted in higher amounts during the day, when these day-flying moths are active. There was minimal divergence found in petal color, which is another potential floral attractant. Female moths responded most strongly to scent from their local host species in olfactometer bioassays, and were more likely to oviposit in, and thereby pollinate, their local host species in no-choice trials. The results suggest that floral scent is an important attractant in this interaction. Local specialization in the pollinator response to a highly specific plant chemistry, thus, has the potential to contribute importantly to patterns of interaction specificity among coevolving plants and highly specialized pollinators.

Geographical matching of volatile signals and pollinator olfactory responses in a cycad brood-site mutualism

“…This was confirmed by the field bioassays, which showed that the main pollinators in the northern populations responded most strongly to (3E)-1,3-octadiene (figure 2a) while those in the southern populations responded most strongly to 2-isopropyl-3-methoxypyrazine (figure 2b). These patterns are consistent with the idea of coevolutionary divergence in obligate brood-site mutualisms [16,19,41].…”

The evolution of floral signals in relation to range overlap in a clade of California Jewelflowers (Streptanthuss.l.)

“…; Friberg et al. ). Additional work at the population and sister‐species scales is needed to understand the degree of intraspecific variation in scent profiles, and the processes that shape inter‐ and intraspecific patterns of scent diversity.…”

“…; Friberg et al. ; Whitehead and Peakall ). Recent experimental evolution work has shown that divergent pollinator selection can cause evolutionary divergence in floral scent phenotypes in just a few short generations in the laboratory (Gervasi and Schiestl ).…”

Improving our chemistry: challenges and opportunities in the interdisciplinary study of floral volatiles

“…60 In this case, it is not known if differences are due to volatile chemistry, but the prodoxid moth lineages that show differential attraction to these plants have been shown in other studies to use volatiles in choosing owers to visit. 50,61 Plant volatile evolution mediated by hybridization, gene duplication, or both, would therefore seem to have a strong potential for mediating at least some radiations of plant lineages, either directly through selection acting on volatiles or indirectly through selection on oral morphological traits (e.g. osmophores) that affect volatile production.…”

“…77 We already know that some plants are able to alter production of VOCs during diurnal cycles to coincide with the activity patterns of their pollinators. 50,87,88 Abiotic inuences, such as increased temperatures, also affect VOC emissions from plants. 89 Will increased temperatures with global change cause adaptive or maladaptive phenotypic shis in VOC emissions?…”