Additive effects of pollinators and herbivores result in both conflicting and reinforcing selection on floral traits

Abstract

Mutualists and antagonists are known to respond to similar floral cues, and may thus cause opposing selection on floral traits. However, we lack a quantitative understanding of their independent and interactive effects. In a population of the orchid Gymnadenia conopsea, we manipulated the intensity of pollination and herbivory in a factorial design to examine whether both interactions influence selection on flowering phenology, floral display, and morphology. Supplemental hand-pollination increased female fitness by 31% and one-quarter of all plants were damaged by herbivores. Both interactions contributed to selection. Pollinators mediated selection for later flowering and herbivores for earlier flowering, while both selected for longer spurs. The strength of selection was similar for both agents, and their effects were additive. As a consequence, there was no. net selection on phenology, whereas selection on spur length was strong. The experimental results demonstrate that both pollinators and herbivores can markedly influence the strength of selection on flowering phenology and floral morphology, and cause both conflicting and reinforcing selection. They also indicate that the direction of selection on phenology will vary with the relative intensity of the mutualistic and antagonistic interaction, potentially resulting in both temporal and among-population variation in optimal flowering time.

Contrasting effects of ploidy level on seed production in a diploid tetraploid system

“…In agreement with our study, lower seed production due to higher levels of seed damage later in the field season was also demonstrated in other systems (e.g. Ehrlén and Münzbergová 2009; Sletvold et al 2015), although the opposite pattern (Ehrlén et al 2015; Konig et al 2015) or no effect (e.g. Varga 2014; Konig et al 2015) have also been reported.…”

“…Consequently, differences in flowering phenologies may lead to different plant–herbivore and plant–pollinator interactions among different cytotypes and potentially be under strong selection as a consequence of these interactions (e.g. Nuismer and Cunningham 2005; Perez-Barrales et al 2013; Jordan et al 2015; Sletvold et al 2015). Only a study by Nuismer and Cunningham (2005) has, however, explicitly assessed the intensity of selection on traits in different cytotypes.…”

Greenhouse gas emissions from dung pats vary with dung beetle species and with assemblage composition

“…lunaris was associated with unexpectedly high methane emissions, it was also the most efficient species in removing dung and reducing CO 2 emissions, even more efficient than mixed assemblages. Thus, functionally efficient organisms may simultaneously increase both desirable and undesirable ecosystem processes [46,47] and different ecosystem services may trade off against each other [48,49]. Across different taxa, many species provide both ecosystem services and disservices.…”

Herbivore-Induced DNA Demethylation Changes Floral Signalling and Attractiveness to Pollinators in Brassica rapa

“…While it has been shown that herbivory can indeed lead to pollinator-relevant changes in floral signalling [64–66], results from studies with different plant- and herbivore systems are often very heterogeneous. In B .…”