Herbivory as an important selective force in the evolution of floral traits and pollinator shifts.

Tania Jogesh,Krissa A Skogen,Robert A Raguso,Rick P Overson

doi:10.1093/aobpla/plw088

Abstract

Floral trait evolution is frequently attributed to pollinator-mediated selection but herbivores can play a key role in shaping plant reproductive biology. Here we examine the role of florivores in driving floral trait evolution and pollinator shifts in a recently radiated clade of flowering plants, Oenothera sect. Calylophus We compare florivory by a specialist, internal feeder, Mompha, on closely related hawkmoth- and bee-pollinated species and document variation in damage based on floral traits within sites, species and among species. Our results show that flowers with longer floral tubes and decreased floral flare have increased Mompha damage. Bee-pollinated flowers, which have substantially smaller floral tubes, experience on average 13% less Mompha florivory than do hawkmoth-pollinated flowers. The positive association between tube length and Mompha damage is evident even within sites of some species, suggesting that Mompha can drive trait differentiation at microevolutionary scales. Given that there are at least two independent shifts from hawkmoth to bee pollination in this clade, florivore-mediated selection on floral traits may have played an important role in facilitating morphological changes associated with transitions from hawkmoth to bee pollination.

Highlights

Herbivores have been cited as an important evolutionary force in the diversification of angiosperms (Futuyma and Agrawal 2009)
We see a clear distinction in the morphological traits of hawkmoth- and beepollinated flowers with bee-pollinated taxa having smaller corollas, floral flares, floral tube lengths, lower nectar volumes and almost no herkogamy (Fig. 2)
Floral traits showed near complete separation based on pollination syndrome (ANOSIM R 1⁄4 0.99, P 1⁄4 0.001) and to a lesser extent based on species (ANOSIM R 1⁄4 0.73, P 1⁄4 0.001)

Summary

Introduction

Herbivores have been cited as an important evolutionary force in the diversification of angiosperms (Futuyma and Agrawal 2009). Since Ehrlich and Raven’s seminal paper on escape-and-radiate coevolution (Ehrlich and Raven 1964), numerous studies have established the importance of herbivores for the evolution of plants at micro- and macroevolutionary scales (Agrawal et al 2012; Agren et al 2013; Coley and Kursar 2014; Becerra 2015).

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Discussion

Conclusion