Garden varieties: how attractive are recommended garden plants to butterflies?

One way the public can engage in insect conservation is through wildlife gardening, including the growing of insect-friendly flowers as sources of nectar. However, plant varieties differ in the types of insects they attract. To determine which garden plants attracted which butterflies, we counted butterflies nectaring on 11 varieties of summer-flowering garden plants in a rural garden in East Sussex, UK. These plants were all from a list of 100 varieties considered attractive to British butterflies, and included the five varieties specifically listed by the UK charity Butterfly Conservation as best for summer nectar. A total of 2659 flower visits from 14 butterfly and one moth species were observed. We performed a principal components analysis which showed contrasting patterns between the species attracted to Origanum vulgare and Buddleia davidii. The “butterfly bush” Buddleia attracted many nymphalines, such as the peacock, Inachis io, but very few satyrines such as the gatekeeper, Pyronia tithonus, which mostly visited Origanum. Eupatorium cannibinum had the highest Simpson’s Diversity score of 0.75, while Buddleia and Origanum were lower, scoring 0.66 and 0.50 respectively. No one plant was good at attracting all observed butterfly species, as each attracted only a subset of the butterfly community. We conclude that to create a butterfly-friendly garden, a variety of plant species are required as nectar sources for butterflies. Furthermore, garden plant recommendations can probably benefit from being more precise as to the species of butterfly they attract

Effects of patch size and density on flower visitation and seed set of wild plants: a pan-European approach

1. Habitat fragmentation can affect pollinator and plant population structure in terms of species composition, abundance, area covered and density of flowering plants. This, in turn, may affect pollinator visitation frequency, pollen deposition, seed set and plant fitness. 2. A reduction in the quantity of flower visits can be coupled with a reduction in the quality of pollination service and hence the plants’ overall reproductive success and long-term survival. Understanding the relationship between plant population size and⁄ or isolation and pollination limitation is of fundamental importance for plant conservation. 3. Weexamined flower visitation and seed set of 10 different plant species fromfive European countries to investigate the general effects of plant populations size and density, both within (patch level) and between populations (population level), on seed set and pollination limitation. 4. Wefound evidence that the effects of area and density of flowering plant assemblages were generally more pronounced at the patch level than at the population level. We also found that patch and population level together influenced flower visitation and seed set, and the latter increased with increasing patch area and density, but this effect was only apparent in small populations. 5. Synthesis. By using an extensive pan-European data set on flower visitation and seed set we have identified a general pattern in the interplay between the attractiveness of flowering plant patches for pollinators and density dependence of flower visitation, and also a strong plant species-specific response to habitat fragmentation effects. This can guide efforts to conserve plant–pollinator interactions, ecosystem functioning and plant fitness in fragmented habitats

Diet breadth, coexistence and rarity in bumblebees

Factors that determine the relative abundance of bumblebee species remain poorly understood, rendering management of rare and declining species difficult. Studies of bumblebee communities in the Americas suggest that there are strong competitive interactions between species with similar length tongues, and that this competition determines the relative abundance of species. In contrast, in Europe it is common to observe several short-tongued species coexisting with little or no evidence for competition shaping community structure. In this study we examine patterns of abundance and distribution in one of the most diverse bumblebee communities in Europe, found in the mountains of southern Poland. We quantify forage use when collecting nectar and pollen for 23 bumblebee species, and examine patterns of co-occurrence and niche overlap to determine whether there is evidence for inter-specific competition. We also test whether rarity can be explained by diet breadth. Up to 16 species were found coexisting within single sites, with species richness peaking in mountain pasture at ~1000m altitude. Results concur with previous studies indicating that the majority of pollen collected by bumblebees is from Fabaceae, but that some bee species (e.g. B. ruderatus) are much more heavily dependent on Fabaceae than others (e.g. B. lucorum). Those species that forage primarily on Fabaceae tended to have long tongues. In common with studies in the UK, diet breadth was correlated with abundance: rarer species tended to visit fewer flower species, after correcting for differences in sample size. No evidence was found for similarity in tongue length or dietary overlap influencing the likelihood of co-occurrence of species. However, the most abundant species (which co-occurred at most sites) occupied distinct dietary niche space. While species with tongues of similar length tended, overall, to have higher dietary niche overlap, among the group of abundant short-tongued species that commonly co-occurred there was marked dietary differentiation which may explain their coexistence

Influence of bioenergy crops on pollinator activity varies with crop type and distance

International audienceCompared to traditional arable crops, second-generation perennial energy crops (PECs) are generally associated with increased biodiversity and ecosystem services, but robust experimental studies on this subject are few. Consequently, the potential for PEC cultivation to contribute to enhanced pollination processes in adjacent farmland remains unclear. In a 4-year field study across multiple sites and two PECs (Miscanthus x giganteus and willow short-rotation coppice), we examine whether pollinator visits to crop margin wildflowers were augmented by PEC cultivation. Each field was paired with two cereal fields, one adjacent to the PEC and one distant, and we recorded wildflower visits to crop margins by three pollinator groups: hoverflies, bumblebees and butterflies/moths. We also quantified floral resources, since crop-specific management seemed a likely means of influencing margin wildflowers and thus pollinator activity. Our results add quantitative support to the suggestion that PECs should enhance ecosystem processes in agri-landscapes. However, benefits were highly context-dependent. Consistent enhancement of pollinator activity in margins of PEC fields was only apparent for willow where the relative frequency of flower visitation was higher for all three pollinator groups compared to adjacent or distant cereals. This distribution was most likely positively associated with the increased availability of preferred food plants in willow margins. In Miscanthus, by contrast, opposing trends arose for different pollinator taxa: Lepidoptera were the only pollinator group more frequently associated with PEC margins; bumblebees showed no variation while hoverflies were comparatively more abundant in distant cereal margins than in other crop types. Future land-use practices should consider how PEC identity affects both target species and ecosystem processes. Tackling anthropogenic climate change through cultivation of willow, in particular, may yield local conservation benefits for both wildflowers and pollinators, although strategic cultivation of PECs to enhance pollination processes in the wider agri-environment may not be achievable

Opportunities to enhance pollinator biodiversity in solar parks

Renewable power capacity is increasing globally in response to energy decarbonisation, with solar photovoltaic (PV) projected to be the dominant renewable. A significant proportion of solar PV is deployed as ground-mounted solar parks with potential implications for the hosting ecosystem. Given their relatively rapid introduction, the impacts on land use and the local environment are poorly understood. However, if deployed and managed strategically, solar parks could offer unique opportunities to enhance the local environment and benefit biodiversity, with implications for ecosystem components such as pollinators. With a focus on north-west Europe, we systematically review the available evidence on how land management practices relevant to solar parks can enhance pollinator biodiversity. We assessed 185 articles for the quantity and agreement of evidence for 27 management interventions and assigned a confidence score to each finding. We show that a range of interventions applied to solar parks could increase their ability to enhance pollinator biodiversity. We then use our assessment to synthesise ten evidence-based recommendations on how to improve solar park management for pollinators by providing foraging and reproductive resources, undergoing considered management practices, increasing landscape heterogeneity and connectivity and providing microclimatic variation. Ensuring beneficial management of rapidly growing solar parks contributes to their wider environmental sustainability, with positive implications for both pollinator conservation and the energy sector in general