Loss of pollinator specialization revealed by historical opportunistic data: Insights from network-based analysis

Ecological patterns of plant-pollinator interactions in the Palouse Prairie

Insect pollinators are essential for natural ecosystems. Without pollination, native plants are less likely to be able to persist. As natural ecosystems have become more fragmented and degraded, interest in their restoration and preservation has increased. Understanding the roles that individual plant and pollinator species play in an ecosystem can assist with these tasks. One way to examine the ecological drivers for patterns of pollination is through module analysis. The Palouse Prairie is a fragmented native prairie that supports high plant and insect diversity and has experienced severe habitat loss. Bees were collected on native plants in prairie fragments in 2022 and 2023 to construct a plant-pollinator network. From this network, modules were computed and analyzed. This network contained 10 modules representing multiple different ecological patterns, including modules grouped by morphological, taxonomic, and phenological similarities. These modules also identified plant-pollinator pairs with specialized relationships. The network was then analyzed to identify plant and insect members that play structural roles in the network. Understanding the patterns of interactions represented in the modules and the network structure may allow for better conservation and restoration of this imperiled ecosystem.

Toward a Functional Trait Approach to Bee Ecology

Functional traits offer an informative framework for understanding ecosystem functioning and responses to global change. Trait data are abundant in the literature, yet many communities of practice lack data standards for trait measurement and data sharing, hindering data reuse that could reveal large-scale patterns in functional and evolutionary ecology. Here, we present a roadmap toward community data standards for trait-based research on bees, including a protocol for effective trait data sharing. We also review the state of bee functional trait research, highlighting common measurement approaches and knowledge gaps. These studies were overwhelmingly situated in agroecosystems and focused predominantly on morphological and behavioral traits, while phenological and physiological traits were infrequently measured. Studies investigating climate change effects were also uncommon. Along with our review, we present an aggregated morphological trait dataset compiled from our focal studies, representing more than 1600 bee species globally and serving as a template for standardized bee trait data presentation. We highlight obstacles to harmonizing this trait data, especially ambiguity in trait classes, methodology, and sampling metadata. Our framework for trait data sharing leverages common data standards to resolve these ambiguities and ensure interoperability between datasets, promoting accessibility and usability of trait data to advance bee ecological research.

Mixed effects of honey bees on pollination function in the Tibetan alpine grasslands

The global expansion of domesticated plant and animal species has profoundly impacted biodiversity and ecosystem functions. However, the spillover effect of non-native honey bees from mass-flowering crops into adjacent natural vegetation on pollination function within plant communities remains unclear. To address this, we conduct field experiments to investigate the ecological impacts of honey bees (Apis mellifera) and a mass-flowering crop (Brassica rapa var. oleifera) on pollinator communities, plant-pollinator interactions, and reproductive performance of wild plants in 48 pollinator-limited alpine grasslands. Our findings indicate that the transition of dominant pollinators from flies to honey bees enhances visitation fidelity of pollinator species and reconfigures pollination interactions due to an increase in competition between honey bees and native pollinator species. Additionally, honey bees increase, decrease or do not alter plant reproductive success, depending on the plant species. Here, we report the mixed effects of honey bees on pollination function in pollinator-limited alpine grasslands.

A bee's-eye view of landscape change: differences in diet of 2 Andrena species (Hymenoptera: Andrenidae) between 1943 and 2021

Declines in pollinating insects have been linked to changes in land cover, affecting the availability of nesting sites and floral resources. Our study is the first analysis of changes in pollen load composition of 2 mining bees, Andrena barbilabris (Kirby) and Andrena flavipes (Panzer) (Hymenoptera: Andrenidae), at the same sites in central England, over 75 years. This provides a unique opportunity to remove spatial variation and review temporal changes in pollen diet within the context of landscape change. We analyzed modern-day pollen load composition for these species and compared it with historical data from the same sites. We then examined potential links between land-use change and the bees' diets. Both bees showed dietary flexibility and lower diet breadth for A. barbilabris, and the bees' foraging strategies appear to have changed. Andrena flavipes collected more pollen taxa in a single load, while A. barbilabris appeared to source pollen from greater distances. Landscape changes at the studied sites have affected the nutritional environment for these bees. Our findings are supported by an existing assessment of floral resources, which found floral diversity has decreased overall in both the habitats used by these bees. However, more research is needed on the nutritional content of pollens used by these bees, both now and historically, to estimate how pollen diversity has changed. The bee's-eye view underlines the importance of understanding how species respond to local changes so that effective conservation strategies can be developed.

Plant-pollinator network change across a century in the subarctic

Animal-mediated pollination is a vital ecosystem service to crops and wild plants, and long-term stability of plant-pollinator interactions is therefore crucial for maintaining plant biodiversity and food security. However, it is unknown how the composition of pollinators and the structure of pollinator interactions have changed across longer time spans relevant to examining responses to human activities such as climate change. We resampled an historical dataset of plant-pollinator interactions across several orders of pollinating insects in a subarctic location in Finland that has already experienced substantial climate warming but little land use change. Our results reveal a dramatic turnover in pollinator species and rewiring of plant-pollinator interactions, with only 7% of the interactions shared across time points. The relative abundance of moth and hoverfly pollinators declined between time points, whereas muscoid flies, a group for which little is known regarding conservation status and responses to climate, became more common. Specialist pollinators disproportionately declined, leading to a decrease in network-level specialization, which could have harmful consequences for pollination services. Our results exemplify the changes in plant-pollinator networks that might be expected in other regions as climate change progresses.

Beyond the Decline of Wild Bees: Optimizing Conservation Measures and Bringing Together the Actors

Wild bees are facing a global decline mostly induced by numerous human factors for the last decades. In parallel, public interest for their conservation increased considerably, namely through numerous scientific studies relayed in the media. In spite of this broad interest, a lack of knowledge and understanding of the subject is blatant and reveals a gap between awareness and understanding. While their decline is extensively studied, information on conservation measures is often scattered in the literature. We are now beyond the precautionary principle and experts are calling for effective actions to promote wild bee diversity and the enhancement of environment quality. In this review, we draw a general and up-to-date assessment of the conservation methods, as well as their efficiency and the current projects that try to fill the gaps and optimize the conservation measures. Targeting bees, we focused our attention on (i) the protection and restoration of wild bee habitats, (ii) the conservation measures in anthropogenic habitats, (iii) the implementation of human made tools, (iv) how to deal with invasive alien species, and finally (v) how to communicate efficiently and accurately. This review can be considered as a needed catalyst to implement concrete and qualitative conversation actions for bees.