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


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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Available from: Anna Brandenburg, Sep 21, 2015
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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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    ABSTRACT: Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows. A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7 °C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8 °C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology. Six years of experimental warming resulted in reductions in nectar volume per floret (64·7 % of control), floret number per capitulum (8·7 %) and capitulum number per plant (32·5 %), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90 % in nectar production per unit area. The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant-pollinator interactions and plant reproduction via induction of allocation shifts for plants growing in communities subject to asymmetric warming. © The Author 2015. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
    Annals of Botany 04/2015; DOI:10.1093/aob/mcv042 · 3.65 Impact Factor
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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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    ABSTRACT: It is estimated that floral deception has evolved in at least 7500 species of angiosperms, of which two thirds are orchids. Epipactis veratrifolia (Orchidaceae) is a model system of aphid mimicry as aphidophagous hoverflies lay eggs on false brood sites on their flowers. To understand the evolutionary ecology of floral deception, we investigated the pollination biology of E. veratrifolia across 10 populations in the Eastern Himalayas. We reconstructed the phylogeny of Epipactis and mapped the known pollination systems of previously studied species onto the tree. Some inflorescences of E. veratrifolia were so infested with aphids while they were still in bud that the some larvae of hoverflies developed to the third instar while flower buds opened. This indicated that adult female hoverflies were partly rewarded for oviposition. Although flowers failed to secrete nectar, they mimicked both alarm pheromones and aphid coloring of to attract female hoverflies as their exclusive pollinators. Phylogenetic mapping indicate that pollination by aphidophagous hoverflies is likely an ancestral condition in the genus Epipactis. We suggest that the biological interaction of aphid (prey), orchid (primary producer) and hoverfly (predator) may represent an intermediate stage between mutualism and deception in the evolution of pollination-by-deceit in E. veratrifolia. Our analyses indicate that this intermediate stage may be used as a model system to interpret the origin of oviposition (brood site) mimicry in Epipactis. We propose the hypothesis that some deceptive pollination systems evolved directly from earlier (partly) mutualistic systems that maintained the fidelity of the original pollinator(s) even though rewards (nectar/ brood site) were lost.
    BMC Plant Biology 03/2014; 14(1):63. DOI:10.1186/1471-2229-14-63 · 3.81 Impact Factor
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    • "Nectar plays multiple roles in plant pollination (floral nectar, FN) and in the indirect defence of plants against herbivores (extrafloral nectar, EFN) (Heil, 2008, 2011; Brandenburg et al., 2009). In addition to its chemical composition , the quantity of nectar secreted also represents an important trait that is positively correlated with pollination success or the resulting indirect defence (Heil et al., 2009; Brandenburg et al., 2012). Plants are therefore capable of adjusting nectar secretion rates to the current needs, and may even re-absorb unconsumed nectar (Pederson et al., 1958; Ziegler and Lü ttge, 1959; Bú rquez and Corbet, 1991; Nicolson, 1995; Heil et al., 2000; Nepi et al., 2001, 2011b; Escalante-Perez et al., 2012). "
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    ABSTRACT: In spite of the ecological and evolutionary importance of nectar, mechanisms controlling its synthesis and secretion remain largely unknown. It is widely believed that nectar is 'secreted phloem sap', but current research reveals a biochemical complexity that is unlikely to stem directly from the phloem. We used the short daily peak in the production of extrafloral nectar by Acacia cornigera to investigate metabolic and proteomic dynamics before, during and after the 2 hours of diurnal secretion. Neither hexoses nor dominating nectar proteins (nectarins) were detected in the phloem before or during nectar secretion, excluding the phloem as the direct source of major nectar components. Enzymes involved in the anabolism of sugars, amino acids and proteins, and nectarins such as invertase, β-1,3-glucanase and thaumatin-like protein, accumulated in the nectary directly before and diminished quantitatively after the daily secretion process. Corresponding genes were expressed almost exclusively in nectaries. By contrast, protein catabolic enzymes were mainly present and active after the secretion peak and might function in the termination of the secretion process. The metabolic machinery for extrafloral nectar production is synthesized and active during concurrent secretion and is degraded thereafter. Knowing the key enzymes involved and the spatiotemporal patterns in their expression will allow the elucidation of mechanisms by which plants control nectar quality and quantity. © 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.
    The Plant Journal 10/2013; 73(4):546–554. DOI:10.1111/tpj.12052 · 5.97 Impact Factor
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