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Hawkmoth Pollinators Decrease Seed Set of a Low-Nectar Petunia axillaris Line through Reduced Probing Time

Institute of Biology, University of Neuchâtel, Emile Argand 13, 2009 Neuchâtel, Switzerland.
Current biology: CB (Impact Factor: 9.57). 07/2012; 22(17):1635-9. DOI: 10.1016/j.cub.2012.06.058
Source: PubMed

ABSTRACT

Although deception of floral pollinators is well known among orchids [1, 2], the majority of animal-pollinated plants secure pollination by nectar rewards. The costs and benefits of nectar production remain poorly understood [3-5]. Here, we developed a crossing design to introgress a low-nectar-volume locus of Petunia integrifolia into the genetic background of P. axillaris. The resulting introgression line resembled P. axillaris but produced only one-third of the nectar volume. When exposed simultaneously to low-nectar and wild-type P. axillaris plants, hawkmoth pollinators reduced their probing duration on low-nectar plants but otherwise did not show any signs of discrimination against these plants. However, reduced probing duration resulted in reduced seed production in the low-nectar plants despite their higher reproductive potential as evidenced by hand pollination. In line with this interpretation, we found a positive correlation between probing duration and seed set, and hawkmoth pollination of low-nectar plants that were manually supplemented with nectar to parental levels yielded seed sets similar to hand pollination. Thus, a simple self-serving pollinator behavior-the adjustment of probing time in response to nectar volume-may select against reducing nectar and protect many plant-pollinator mutualisms against a drift toward parasitism. VIDEO ABSTRACT:

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    • "Possibly because the conflict does not involve interdependencies, the system has yielded experimental evidence for a variety of partner control mechanisms, including punishment, partner switching and social prestige[69,105]. Asymmetric cheating options are highly abundant in mutualisms, with experimental evidence that contingent helping may occur even in plants and insects106107108. For within-species cooperation, evidence for payto-stay in cooperatively breeding systems[109]provides a class of examples for helping acts like brood care or territorial defense, though Hamilton & Taborsky[110]found that if the threat of eviction alone enforces helping, subordinates will not overcompensate for the costs they impose on dominants. "
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    ABSTRACT: Mutual helping for direct benefits can be explained by various game theoretical models, which differ mainly in terms of the underlying conflict of interest between two partners. Conflict is minimal if helping is self-serving and the partner benefits as a by-product. In contrast, conflict is maximal if partners are in a prisoner’s dilemma with both having the pay-off-dominant option of not returning the other’s investment. Here,we provide evolutionary and ecological arguments for why these two extremes are often unstable under natural conditions and propose that interactions with intermediate levels of conflict are frequent evolutionary endpoints. We argue that by-product helping is prone to becoming an asymmetric investment game since even small variation in by-product benefits will lead to the evolution of partner choice, leading to investments by the chosen class. Second, iterated prisoner’s dilemmas tend to take place in stable social groups where the fitness of partners is interdependent, with the effect that a certain level of helping is self-serving. In sum, intermediate levels of mutual helping are expected in nature, while efficient partner monitoring may allow reaching higher levels © 2016 The Author(s) Published by the Royal Society. All rights reserved.
    Full-text · Article · Feb 2016 · Philosophical Transactions of The Royal Society B Biological Sciences
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    • "By virtue of their close mutualistic association, pollinator population density and activity are largely dependent upon floral resource availability and quality (Hanley et al., 2008, 2014; Brandenburg et al., 2012; Scaven and Rafferty, 2013). For example , pollinators typically show fidelity towards plants producing more and higher quality nectar (Lake and Hughes, 1999; Mitchell et al., 2004), such that nectar production directly affects pollinator activity (Klinkhamer and de Jong, 1990; Kudo and Harder, 2005) and pollinator community structure (Potts et al., 2004). "
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    Preview · Article · Apr 2015 · Annals of Botany
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    • "Most flowering plants depend primarily on animals for sexual reproduction, offering edible or non-edible rewards to their pollen vectors [1-3]. However, some “deceptive flowers” offer no rewards [4-6]. "
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    Full-text · Article · Mar 2014 · BMC Plant Biology
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