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Traits morphologiques et biochimiques impliqués dans la spécialisation de Trollius europaeus sur les pollinisateurs prédateurs de graines Chiastocheta spp.

Abstract : Interactions between species are a major driving force in evolution. We show here which morphological and biochemical traits evolved during the specialisation of the European globeflower (Trollius europaeus) on seed-eating pollinator flies (Chiastocheta spp). The globular shape is a key factor in the specific attraction of chiastochetes. Globular flowers produce more seeds (4%, they suffer higher predation but are better pollinated) and moreover export more pollen (85%) than artificially open flowers. An adaptive dynamics model shows that the evolution of the globular shape requires a minimal pollination efficiency by chiastochetes relatively to alternative pollinators that do not eat seeds, but also a maximal efficiency: if the chiastochetes are “too” efficient, to attract a lot of them rather than a few confers no advantage. The attraction of pollinators is also mediated by olfactive signals. Several volatile compounds emitted by the globeflower trigger an electrophysiological response in chiastochetes (methyl salicylate, Z-jasmone, β-caryophyllene, germacrene D, E,E-α-farnesene, linalool). Field behavioural observations of chiastochetes visits have shown that the variability of the volatile compounds inside the flowers explains a part of the variability of the visits, together with morphological and pigmentation traits. Interactions between plants and seed predators are conflictual: the plants tend to reduce predation costs. A flavonoid close to luteolin, adonivernith, accumulates in the carpel walls when the damages caused by the larvae increase, leading to a reduction of predation intensity. The six Chiastocheta studied species have different exploitation patterns in the fruit, they induce and are affected by adonivernith in specific ways: this chemical defence could be involved in the sympatric speciation of the genus. The traits involved in the globeflower specialisation on chiastochetes are simultaneously mutualistic (globular floral morphology, floral colour and volatile compounds) and antagonistic (chemical defence against the larvae). The contradictions of this trait mosaic are a factor of evolution.
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https://tel.archives-ouvertes.fr/tel-00408744
Contributor : Sébastien Ibanez <>
Submitted on : Monday, August 3, 2009 - 9:42:50 AM
Last modification on : Friday, November 6, 2020 - 3:40:11 AM
Long-term archiving on: : Saturday, November 26, 2016 - 11:20:19 AM

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  • HAL Id : tel-00408744, version 1

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Sébastien Ibanez. Traits morphologiques et biochimiques impliqués dans la spécialisation de Trollius europaeus sur les pollinisateurs prédateurs de graines Chiastocheta spp.. Ecologie, Environnement. Université Joseph-Fourier - Grenoble I, 2009. Français. ⟨tel-00408744⟩

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