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Distasteful nectar deters floral robbery

Distasteful nectar deters floral robbery

Barlow, Sarah E., Wright, Geraldine A., Ma, Carolyn, Barberis, Marta, Farrell, Iain W., Marr, Emily C., Brankin, Alice, Pavlik, Bruce M. and Stevenson, Philip (2017) Distasteful nectar deters floral robbery. Current Biology, 27 (16). 2552-2558.e3. ISSN 0960-9822 (Print), 1879-0445 (Online) (doi:10.1016/j.cub.2017.07.012)

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Abstract

Toxic nectar is an ecological paradox[1,2]. Plants divert substantial resources to produce nectar that attracts pollinators [3], but toxins in this reward could disrupt the mutualism and reduce plant fitness [4]. Alternatively, such compounds could protect nectar from robbers [2], provided they do not significantly alter pollinator visitation to the detriment of plant fitness [1,5–8]. Indeed, very few studies have investigated the role of plant toxins in nectar for defence against nectar robbers [4,9,10]. Here, we compared two Aconitum species (A. napellus and A. lycoctonum) that have flowers specialized for long-tongued bumblebee pollinators (Bombus hortorum) but are occasionally robbed by short-tongued bumblebees (B. terrestris) [6,11–13]. Pollinator visits to flowers were much more frequent than by robbers but visits correlated negatively with nectar alkaloid concentration and declined sharply between 200-380ppm. However, alkaloid concentrations of > 20ppm were deterrent to B. terrestris suggesting robbers were less tolerant of nectar alkaloids. Nectar of both plant species contained similar concentrations of carbohydrates and toxic alkaloids, but A. lycoctonum was more likely to secrete nectar in each flower and was also visited more frequently by pollinators and robbers.  We conclude that alkaloids in Aconitum sp. nectar affect rates of both pollinator visitation and robbery but may have co-evolved with nectar availability to maintain the fitness benefits of specialized plant-pollinator relationships. Chemical defence of nectar is, however, ultimately constrained by pollinator gustatory sensitivity.

Item Type: Article
Uncontrolled Keywords: Alkaloids, Bombus, Aconitum, Bumblebees, Chemical defense, Nectar larceny, Nectar toxin, Specialized pollinators, Rana automated monitoring
Subjects: S Agriculture > S Agriculture (General)
Faculty / Department / Research Group: Faculty of Engineering & Science
Faculty of Engineering & Science > Natural Resources Institute
Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department
Faculty of Engineering & Science > Natural Resources Institute > Chemical Ecology Research Group
Last Modified: 11 Apr 2018 11:51
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: GREAT a
URI: http://gala.gre.ac.uk/id/eprint/17458

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