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Urbanization effects on floral morphology and plant-pollinator relationships

Abstract : The expansion of urban areas is known to impact the composition of plant and pollinator communities. However, the effects of urbanization on the interdependency between both communities, and the subsequent evolutionary consequences, are still poorly studied. First, we tried to identify along an urbanization gradient which factors shape plant and pollinator communities. Second, we tested the existence of intra-specific evolutionary divergences of plant reproductive characteristics between populations from urban and rural origins. For these purposes, we combined the analysis of data collected in the Ile-de-France region originating from citizen science projects, and we set up a reciprocal transplantation experiment involving four plant species commonly found in this region. We found that floral morphology was the most frequently implicated factor in the observation of insect families along the gradient. Insect families with positive affinity to impervious areas prefer tubular corollas, while families with negative affinity prefer non-tubular (open) corollas. Urbanization modifies the composition of plant communities, by selecting in particular autogamous and non-entomophilous species. Altogether, our results point towards a functional loss of pollinators along with urbanization. A detailed analysis of the species Cymbalaria muralis suggests a greater reproductive benefit in allocating more resources to flower production in urban plantation sites. As a consequence, plants from urban origin tend to produce more flowers compared to plants from rural origin, at the expense of ovule production per flower and flower coloration. This evolutionary divergence could be explained by shifts in pollinator behaviour induced by higher habitat fragmentation in urban areas. This thesis reveals that shifts in the abundance, in the behaviour or in the functional floral affinities of pollinators, induced by urbanization, could act as selection agents on spontaneous plant species.
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Submitted on : Friday, December 15, 2017 - 4:58:13 PM
Last modification on : Wednesday, October 14, 2020 - 3:39:55 AM

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  • HAL Id : tel-01665328, version 1

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James Desaegher. Urbanization effects on floral morphology and plant-pollinator relationships. Symbiosis. Université Paris Saclay (COmUE), 2017. English. ⟨NNT : 2017SACLS408⟩. ⟨tel-01665328⟩

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