In the city, the seasonal patterns of activity of insect pollinators could be disturbed by the urban microclimate as well as by the presence of ornamental flora. To study this phenomenon, Vincent Zaninotto and his collaborators monitored the activity of insect pollinators in Paris and in the natural environment, from late winter to autumn. In their article published in the journal Ecology and Evolution, they highlight the extension of the period of activity of urban insects, which can have consequences on the efficiency of pollination.
Key-words : Pollination, Urban Ecology, Seasonality
The urban environment modifies the composition of pollinator communities. But it can also influence their seasonality, or “phenology”, through its climate and the plant assemblages it hosts. Indeed, in cities, the urban heat island effect generates higher temperatures. On the other hand, the ornamental flora managed by man can provide artificial resources for pollinators, even off-season.
To better understand this phenomenon and its consequences on the function of pollination, Vincent Zaninotto and his collaborators have monitored the composition and activity of insect pollinators communities throughout the pollination season: from late winter to autumn. Working with the Station d’Ecologie Forestière de Fontainebleau (Université de Paris) and the CEREEP ECOTRON – Ile de France (ENS, CNRS), they were able to carry out this monitoring in parallel within the city of Paris and in natural areas of the Seine-et-Marne region. In order to compare the activity of pollinators in these two habitats, the monitoring was focused on standardised floral assemblages made up of two plant species: white mustard (Sinapis alba), and bird’s-foot trefoil (Lotus corniculatus).
Their team was indeed able to observe differences in seasonal foraging activity between the urban and natural environments. Several categories of pollinators (small wild bees, bumble bees, honey bees) were significantly more active on our floral assemblages in the city, especially in early spring and autumn. This resulted in differences in pollination efficiency between the two habitats. Thus, during springtime, the reproductive success of L. corniculatus was greatest in the city, where the bumble bees displayed earlier activity. Similarly, the reproductive success of S. alba was higher in the urban environment, yet all year long.
Published in the journal Ecology and Evolution under the title « Broader phenology of pollinator activity and higher plant reproductive success in an urban habitat compared to a rural one », these results suggest different phenological adaptations to the urban environment for the different categories of pollinators. Overall, it would seem that the extended period of activity observed in cities for insect pollinators could improve the efficiency of the pollination function and the reproductive success of some plant species in urban settings.
iEES Paris members:
Vincent Zaninotto, Isabelle Dajoz, Xavier Raynaud, Yvan Kraepiel, Emmanuel Gendreau, Eric Motard.
ZANINOTTO Vincent, Doctorant (CIFRE Sorbonne Université et Ville de Paris
Zaninotto V, Raynaud X, Gendreau E, et al. Broader phenology of pollinator activity and higher plant reproductive success in an urban habitat compared to a rural one. Ecol Evol. 2020;00:1–15. https://doi.org/10.1002/ece3.6794
Syrphe porte-plume (Sphaerophoria scripta), un visiteur assidu de la moutarde blanche (Sinapis alba) du printemps à l’automne. (©Benoît Geslin)