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Research article - Peer-reviewed, 2022

Pollinator selection against toxic nectar as a key facilitator of a plant invasion

Egan, Paul; Stevenson, Philip C.; Stout, Jane C.


Plant compounds associated with herbivore defence occur widely in floral nectar and can impact pollinator health. We showed previously that Rhododendron ponticum nectar contains grayanotoxin I (GTX I) at concentrations that are lethal or sublethal to honeybees and a solitary bee in the plant's non-native range in Ireland. Here we further examined this conflict and tested the hypotheses that nectar GTX I is subject to negative pollinator-mediated selection in the non-native range, but that phenotypic linkage between GTX I levels in nectar and leaves acts as a constraint on independent evolution. We found that nectar GTX I experienced negative directional selection in the non-native range, in contrast to the native Iberian range, and that the magnitude and frequency of pollinator limitation indicated that selection was pollinator-mediated. Surprisingly, nectar GTX I levels were decoupled from those of leaves in the non-native range, which may have assisted post-invasion evolution of nectar without compromising the anti-herbivore function of GTX I (here demonstrated in bioassays with an ecologically relevant herbivore). Our study emphasizes the centrality of pollinator health as a concept linked to the invasion process, and how post-invasion evolution can be targeted toward minimizing lethal or sub-lethal effects on pollinators.


phenotypic selection; post-invasion evolution; toxic nectar; plant–herbivore–pollinatorinteractions

Published in

Philosophical Transactions B: Biological Sciences
2022, volume: 377, number: 1853

Authors' information

Swedish University of Agricultural Sciences, Department of Plant Protection Biology
Stevenson, Philip C.
University of Greenwich
Stout, Jane C.
Trinity College Dublin

Associated SLU-program

SLU Network Plant Protection

Sustainable Development Goals

SDG15 Life on land

UKÄ Subject classification

Evolutionary Biology

Publication Identifiers


URI (permanent link to this page)