La diversité des interactions plantes-pollinisateurs : Un pré-requis indispensable à la stabilité des écosystèmes

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Functional Diversity of Plant–Pollinator Interaction Webs Enhances the Persistence of Plant Communities

Pollination is exclusively or mainly animal mediated for 70% to 90% of angiosperm species. Thus, pollinators provide an essential ecosystem service to humankind. However, the impact of human-induced biodiversity loss on the functioning of plant–pollinator interactions has not been tested experimentally. To understand how plant communities respond to diversity changes in their pollinating fauna, we manipulated the functional diversity of both plants and pollinators under natural conditions. Increasing the functional diversity of both plants and pollinators led to the recruitment of more diverse plant communities. After two years the plant communities pollinated by the most functionally diverse pollinator assemblage contained about 50% more plant species than did plant communities pollinated by less-diverse pollinator assemblages. Moreover, the positive effect of functional diversity was explained by a complementarity between functional groups of pollinators and plants. Thus, the functional diversity of pollination networks may be critical to ecosystem sustainability

Biodiversité et fonctionnement des réseaux d'interactions plantes-pollinisateurs

National audienc

Cycles de vie, variabilite morphologique et polymorphisme pollinique chez quelques endemiques pyreneennes

INIST T 77628 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

L'influence des pollinisateurs sur la diversité végétale

International audienc

La pollinisation: un service écosystémique basé sur des réseaux d'interactions complexes

National audienc

Keeping Up with Insect Pollinators in Paris

There is growing interest in urban pollinator communities, although they may be subject to biotic homogenization in densely artificial landscapes. Paris (France) is one of the densest cities in the world, yet over the years many insect pollinator species have been reported there. We conducted in-depth surveys of Parisian green spaces for two years, in order to improve our knowledge of these assemblages. We explored several types of green spaces, monitoring pollinators throughout their activity season. We listed 118 species of wild bees and 37 species of hoverflies, updating pre-existing lists with 32 additional species. Bee assemblages showed functional diversity with 18.5% parasitic species and 17.7% oligolectic species. We also found several bee and hoverfly species under special conservation status. Over the study period, we observed seasonal succession of species, with diversified phenological niches. The greatest taxonomic and functional diversity was found in green spaces combining several habitats with ecological management. Despite its very dense urbanism, Paris is home to diverse pollinator communities. As a result, nearly half of the wild bee species of the wider Ile-de-France administrative region can be found within the city. This highlights the need to also consider dense urban environments in insect pollinator conservation strategies.</jats:p

Plant size effects on allocation to male and female functions in pearl millet, a hermaphroditic wind-pollinated species

In hermaphroditic higher plants, reproductive fitness can be achieved through male and female functions. The relative allocations to reproduction by maternal and paternal investments define the gender of each individual. In wind-pollinated species, the theory predicts that gender should evolve with plant size, the largest plants investing the most in male function. More specifically, the tallest plants should exhibit the highest degree of maleness, because pollen dispersal is most effective when the release point is high. We searched for potential variation in gender with plant size in pearl millet (Pennisetum typhoides), where each plant produces several shoots. Size was estimated by using four parameters, namely height, stem diameter, total leaf area, and vegetative weight, for shoots and for plants. Gender was estimated as the pollen to ovule (P:O) ratio for each shoot or plant. We found that allocation to male function is very variable, both between shoots within a plant and between plants. Most of the difference observed is correlated with differences in the weight of the shoots or plants, the heaviest ones having the highest P:O ratios. The theoretical prediction that maleness should increase with plant height was not fulfilled. The parameter used to estimate plant size seems to have a great influence on the ability to detect gender variation with size. The allocation to reproduction (defined as the weight of seeds, stamens, floral parts, and rachis of the spike) represented a decreasing proportion of total plant weight; also, the heavier the plant, the higher the proportion of this allocation devoted to male function. Since pearl millet is a cultivated species, this may be due to the fact that the domestication process, by selecting for larger plants, involuntarily selected for maleness by favoring the largest plants. Key words: pearl millet, resource allocation, sexual function, plant size. </jats:p