Effect of pollination strategy, phylogeny and distribution on pollination niches of Euro‐Mediterranean orchids

Abstract

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. We constructed a database reporting 1,278 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. 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. 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.

Cheating in arbuscular mycorrhizal mutualism: a network and phylogenetic analysis of mycoheterotrophy

“…The MaarjAM database is a web‐based database (http://maarjam.botany.ut.ee; accessed in June 2019 after a very recent update) of publicly available sequences of Glomeromycotina fungi, with information on the host plants, geographical location and biomes for the recorded interactions (Öpik et al , 2010). We used an approach with a compiled network, where all locally described physical mycelial interactions between species are merged and studied at larger scales (as in Joffard et al , 2019). Although such a compiled network can be sensitive to several biases (see Discussion), it offers unique opportunities to study the emergence of mycoheterotrophy in a large evolutionary and ecological perspective (e.g.…”

“…By assembling networks at a regional scale, Joffard et al . (2019) showed that specialization of orchids toward pollinators was higher in deceptive cheaters (both sexual and food deceits) than in cooperative nectar‐producing species, and Genini et al . (2010) showed that a network dominated by cooperative pollinators was nested, whereas another network dominated by nectar‐thieving insects was more modular.…”

Effects of species traits, motif profiles, and environment on spatial variation in multi‐trophic antagonistic networks

“…Indeed, a recent study by Joffard et al. () outlined a promising technique to study such synergistic effects. Environmental and ecological perturbations are realized at a local scale, and thus, reconciling the differences in the predictive capacities of ecological network models at both local and regional scales is paramount for anticipating species‐specific responses to change.…”

“…Moreover, the results from the environmental drivers of interaction turnover demonstrated a correlation between environmental drivers and interaction turnover suggesting that synergistic effects of both environmental and ecological drivers may be responsible for local realizations of these regional food webs. Indeed, a recent study by Joffard et al (2019) outlined a promising technique to study such synergistic effects. Environmental and ecological perturbations are realized at a local scale, and thus, reconciling the differences in the predictive capacities of ecological network models at both local and regional scales is paramount for anticipating species-specific responses to change.…”

Latitudinal variation in mycorrhizal diversity associated with a European orchid

“…Spiranthes spiralis is a long-lived terrestrial orchid species that is widespread throughout the Mediterranean region yet is in decline in northwest Europe (Jacquemyn & Hutchings, 2010). It is a nectar rewarding species that is pollinated by generalist bees, mainly bumblebees, and occasionally honeybees, in both the Mediterranean and in Ireland (Duffy & Stout, 2011;Petanidou, Duffy, Karatza, & Kantsa, 2013;Joffard, Massol, Grenié, Montgelard, & Schatz, 2019). It generally has high fruit set with approximately 80% of its flowers setting fruit, although per capita fruit set may be reduced in large populations when pollinators are limiting (Petanidou et al, 2013).…”