Using Matching Traits to Study the Impacts of Land-Use Intensification on Plant–Pollinator Interactions in European Grasslands: A Review

Abstract

Permanent grasslands are suitable habitats for many plant and animal species, among which are pollinating insects that provide a wide range of ecosystem services. A global crisis in pollination ecosystem service has been highlighted in recent decades, partly the result of land-use intensification. At the grassland scale, however, the underlying mechanisms of land-use intensification that affect plant–pollinator interactions and pollination remain understudied. In this review, we first synthesise the literature to provide new insights into the relationships between land-use intensification and pollination by using matching community and interaction traits. We then identify knowledge gaps and summarise how land-use intensification of grassland influences floral traits that may in turn be associated with modifications to pollinator matching traits. Last, we summarise how these modifications may affect pollination function on permanent grasslands. Overall, land-use intensification may lead to a shift in flower colour, a decrease in mean nectar tube depth and a decrease in reward production and pollen quality at the community level. This, in turn, may generate a decrease in pollinator mouthparts length and body size, that may favour pollinators that require a low amount of floral reward. We found no study citing the effect of land-use intensification on volatile organic compounds emitted by flowers despite the importance of these molecules in pollinator community composition. Overall, our review highlighted major knowledge gaps about the effects of land-use intensification on plant–pollinator interactions, and suggests that land-use intensification could favour plants with generalised floral traits that adversely affect pollination.

Intensive grazing alters the diversity, composition and structure of plant-pollinator interaction networks in Central European grasslands

“…Depending on their geographic location, environmental conditions and the type and stocking rate of herbivores, pastures could be dominated by grazing-tolerant plant species with either generalist or specialist floral functional traits. A recent review has highlighted the lack of data on the effect of grazing on floral traits, with the available research indicating that generalist flowers could be favoured [31]. However, some studied reveal that Fabaceae, which have quite specialized flowers, are often dominant in intensive pastures throughout Europe (i.e.…”

Flowers of ruderal species are numerous but small, short and low‐rewarding

“…Exploring weed floral phenotypes in more detail by considering supplementary floral traits such as scents or colours and by studying weed pollinators could also help to understand the differences we discovered between the flowers of weeds and grassland species flowers (Junker and Parachnowitsch 2015). Moreover, studying plant–pollinator trait matching could help to better understand these results (Goulnik et al 2021). At last, these observed discrepancies could be related to our datasets, limited in the number of species and not necessarily representative of the two floras being compared.…”

“…Since we found that floral traits are linked to CSR strategies, which are modified by agricultural practices (Kazakou et al 2016), it is possible that weed management could also affect the available floral resources in agroecosystems. High‐intensity land use in grasslands is already known to shape floral resources by homogenising floral traits, inducing changes in flower colour, nectar tube depth or resource production (Goulnik et al 2021). Diversifying agricultural practices at the landscape level to increase the functional diversity of weeds could contribute to diversify the flower resource for pollinators (Fründ et al 2010) as well as provide the numerous other ecosystem services expected from weeds, such as producing food resources for livestock (Genty et al 2023a) and natural enemies (Serée et al 2023) but also supporting processes contributing to soil fertility, such as decomposition (Bopp et al 2022).…”

Integration of historic collections can shed light on patterns of change in plant–pollinator interactions and pollination service

“…Plant–plant and plant–pollinator interactions depend, at least to some degree, on the functional trait matching between partners (i.e. Goulnik et al, 2021). Anthropogenic change can alter this functional fit between partners by either changing the composition and abundance of species within a community (as discussed above) or by creating new selection pressures or induce phenotypic plasticity, resulting in floral and pollinator trait changes (Descamps et al, 2021; Parra‐Tabla et al, 2021; Thompson et al, 2021).…”