Résumé
1. Pollination niches are important components of ecological niches and
have played a major role in the diversification of Angiosperms. In this
study, we focused on Euro-Mediterranean orchids, which use diverse
pollination strategies and interact with various functional groups of
insects. In these orchids, we investigated the determinants of pollination
niche breadth and overlap by analysing the orchid-pollinator network and
the factors that may have shaped it. 2. We constructed a database
reporting 1278 interactions between 243 orchid and 773 pollinator species
based on a thorough literature review. We then focused on 153 orchid
species for which phylogenetic data were available. We used Bayesian
phylogenetic mixed models to study the relationship between specialisation
(as estimated by the degree and degree in the projected network),
pollination strategy and breadths of orchids’ spatial and temporal
distributions, while correcting for the effect of phylogenetic
relationships among orchid species and sampling effort. We then used a
singular value decomposition of the orchid-pollinator matrix combined to a
redundancy and variation partitioning analyses to investigate the
determinants of similarity in pollination niches between orchids. 3.
Specialisation was higher in deceptive than in nectar-producing orchids
and decreased with the breadth of orchids’ spatial distribution. When
interactions were considered at the insect family level, similarity in
pollination niches between orchids was solely explained by their
pollination strategy and phylogeny. By contrast, when they were considered
at the insect species level, this similarity was primarily explained by
their geographical range and flowering time, although other factors had
significant effects as well, with orchids using the same pollination
strategy, being closely related and growing in the same habitats sharing
more insect species than expected. 4. Synthesis. Specialisation in
orchid-pollinator interactions depends on orchids’ pollination strategy
and geographical range. The pool of insect families with which orchids
interact depends on their pollination strategy and phylogeny, with
consistent associations between some functional or phylogenetic groups of
orchids and some families of pollinators. By contrast, the pool of insect
species with which orchids interact depends on their spatio-temporal
distribution, suggesting that at a finer scale, orchid-pollinator
interactions are more opportunistic than previously thought.