Winter Active Bumblebees (Bombus terrestris) Achieve High Foraging Rates in Urban Britain

Background: Foraging bumblebees are normally associated with spring and summer in northern Europe. However, there have been sightings of the bumblebee Bombus terrestris during the warmer winters in recent years in southern England. But what floral resources are they relying upon during winter and how much winter forage can they collect? Methodology/Principal Findings: To test if urban areas in the UK provide a rich foraging niche for bees we set up colonies of B. terrestris in the field during two late winter periods (2005/6 & 2006/7) in London, UK, and measured their foraging performance. Fully automatic radio-frequency identification (RFID) technology was used in 2006/7 to enable us to record the complete foraging activity of individually tagged bees. The number of bumblebees present during winter (October 2007 to March 2008) and the main plants they visited were also recorded during transect walks. Queens and workers were observed throughout the winter, suggesting a second generation of bee colonies active during the winter months. Mass flowering shrubs such as Mahonia spp. were identified as important food resources. The foraging experiments showed that bees active during the winter can attain nectar and pollen foraging rates that match, and even surpass, those recorded during summer. Conclusions/Significance: B. terrestris in the UK are now able to utilise a rich winter foraging resource in urban parks and gardens that might at present still be under-exploited, opening up the possibility of further changes in pollinato

16S rRNA assessment of the influence of shading on early-successional biofilms in experimental streams

Elevated nutrient levels can lead to excessive biofilm growth, but reducing nutrient pollution is often challenging. There is therefore interest in developing control measures for biofilm growth in nutrient-rich rivers that could act as complement to direct reductions in nutrient load. Shading of rivers is one option that can mitigate blooms, but few studies have experimentally examined the differences in biofilm communities grown under shaded and unshaded conditions. We investigated the assembly and diversity of biofilm communities using in situ mesocosms within the River Thames (UK). Biofilm composition was surveyed by 454 sequencing of 16S amplicons (∼400 bp length covering regions V6/V7). The results confirm the importance of sunlight for biofilm community assembly; a resource that was utilized by a relatively small number of dominant taxa, leading to significantly less diversity than in shaded communities. These differences between unshaded and shaded treatments were either because of differences in resource utilization or loss of diatom-structures as habitats for bacteria. We observed more co-occurrence patterns and network interactions in the shaded communities. This lends further support to the proposal that increased river shading can help mitigate the effects from macronutrient pollution in rivers

Anthropogenic noise disrupts mate choice behaviors in female Gryllus bimaculatus

By assessing the sexual signals produced by conspecifics, individuals can make informed decisions on the best choice of mate, which can lead to reproductive fitness benefits. However, these communication systems are often vulnerable to disruption by conflicting with stimuli present in the environment. Anthropogenic noise may act as one such disruptive stimulus, leading to inefficient mate choice decisions and, thus, reductions to an animal’s fitness. In this study, the mate choice behaviors of female Gryllus bimaculatus were tested when presented with artificial male courtship songs of differing “quality” under different acoustic conditions. In ambient noise conditions, females significantly preferred mates paired with higher-quality songs, indicated by increased mating rates and reduced latency to mate. However, this mate selection pattern was disrupted in both traffic and white noise conditions. Additionally, “high-quality” courtship songs had an increased mounting latency in traffic and white noise conditions, when compared to ambient noise conditions. Making nonoptimal mating decisions, such as the ones seen here, can lead to deleterious fitness consequences, alter population dynamics, and weaken sexual selection, unless individuals adapt to cope with anthropogenic interference

What evidence exists on the impacts of large herbivores on climate change? A systematic map protocol

Background- In recent years there has been an increased focus on the role of large herbivores in ecosystem restoration and climate change mitigation. There are multiple processes by which large herbivores could potentially influence climate feedback and forcing effects, but the evidence has not yet been synthesised in a systematic and accessible format. Grazing, browsing, trampling, defecation, and seed dispersal by large herbivores can influence vegetation and soils in ways that may directly or indirectly contribute to climate change or mitigation. For example, changes in vegetation could impact wildfire regimes, carbon storage, and albedo, with ultimate impacts on climate. These processes may be influenced by herbivore species composition, density, and functional traits. The main aim of this systematic map is to synthesise the range of research on climate feedback and forcing effects from large herbivores (≥ 10 kg) in terrestrial ecosystems. We also aim to identify knowledge clusters and gaps in the research base, as well as assessing the potential for quantitative analyses. Methods- A search of peer-reviewed and grey literature will be conducted using a range of bibliographic databases, search engines and websites. The search strategy will involve using a pre-defined search string with Boolean operators. All search results will be screened for relevance according to specific eligibility criteria. Screening will be conducted in two stages: all articles will initially be screened by title and abstract, then those that meet the eligibility criteria will be screened by full text. At both stages, articles will be excluded if they don’t meet all eligibility criteria or if they meet any exclusion criteria. All articles included as eligible after full text screening will be coded. At each stage (of screening and coding) a proportion of articles will be processed independently by two reviewers to assess inter-reviewer reliability and resolve differences. The evidence will be presented in a searchable database with accompanying visual outputs. A narrative synthesis will be provided outlining the range and distribution of evidence, knowledge gaps and clusters, potential bias, and areas for further research

Anthropogenic noise disrupts mate searching in Gryllus bimaculatus

Many animals use acoustic communication as a means of sending important biological information, such as their location, to potential receivers. However, anthropogenic noise is known to affect the ability of some species to either produce or receive signals, which may influence their reproductive success. In this study, we investigate the effect of anthropogenic noise on the mate searching behaviors of the field cricket Gryllus bimaculatus. To accomplish this, phonotaxis trials were conducted with female field crickets under different acoustic conditions, and their ability to detect and move towards conspecific male calls was assessed. The presence of traffic noise reduced the likelihood that the female would approach the male calls and also reduced the time that the female spent attending to the calling stimulus before making her decision. However, the presence of white noise did not reduce the likelihood of approaching the calling speaker, indicating that the average amplitude of anthropogenic noise is, alone, not important in this conflict, but frequency and fluctuations in the stimulus or other characteristic might be. This study supports the hypothesis that anthropogenic noise does indeed influence the detectability of acoustic mate location signals, thus disrupting mate searching behavior

Spatio-temporal dynamics of bumblebees foraging under predation risk

We analyze 3D flight paths of bumblebees searching for nectar in a laboratory experiment with and without predation risk from artificial spiders. For the flight velocities we find mixed probability distributions reflecting the access to the food sources while the threat posed by the spiders shows up only in the velocity correlations. The bumblebees thus adjust their flight patterns spatially to the environment and temporally to predation risk. Key information on response to environmental changes is contained in temporal correlation functions, as we explain by a simple emergent model.Comment: Accepted for publication in PR

Zooming into plant-flower visitor networks: an individual trait-based approach

Understanding how ecological communities are structured is a major goal in ecology. Ecological networks representing interaction patterns among species have become a powerful tool to capture the mechanisms underlying plant-animal assemblages. However, these networks largely do not account for inter-individual variability and thus may be limiting our development of a clear mechanistic understanding of community structure. In this study, we develop a new individual-trait based approach to examine the importance of individual plant and pollinator functional size traits (pollinator thorax width and plant nectar holder depth) in mutualistic networks. We performed hierarchical cluster analyses to group interacting individuals into classes, according to their similarity in functional size. We then compared the structure of bee-flower networks where nodes represented either species identity or trait sets. The individual trait-based network was almost twice as nested as its species-based equivalent and it had a more symmetric linkage pattern resulting from of a high degree of size-matching. In conclusion, we show that by constructing individual trait-based networks we can reveal important patterns otherwise difficult to observe in species-based networks and thus improve our understanding of community structure. We therefore recommend using both trait-based and species-based approaches together to develop a clearer understanding of the properties of ecological networks

Winter activity unrelated to introgression in British bumblebee Bombus terrestris audax

Bombus terrestris is a bumblebee with a wide geographic range, with subspecies showing a variety of local adaptations. Global export of commercially-reared B. terrestris started in the 1980s; the bees are a mixture of subspecies bred for ease of rearing, bivoltinism and large nests. This paper investigated whether the increase in bivoltinism in UK resident B. terrestris audax populations was related to introgression with imported foreign subspecies. Workers were collected from wild populations in London and Bristol, as well as two commercial suppliers. Fourteen microsatellite loci were used to study population structure, hybridisation, and introgression. No introgression with commercial B. t. dalmatinus was detected in wild populations. Hence, the increase in winter activity appears unrelated to introgression

Ground beetle assemblages in Beijing’s new mountain forests

Mature forests have been almost completely destroyed in China’s northern regions, but this has been followed by large-scale reforestation in the wake of environmental degradation. Although future forest plantations are expected to expand over millions of hectares, knowledge about the ecology and biodiversity of China’s replanted forests remains very limited. Addressing these knowledge gaps, we recorded ground beetle (Coleoptera: Carabidae) communities in five secondary forest types: plantations of Chinese Pine (Pinus tabulaeformis) and Prince Rupprecht’s Larch (Larix principis-rupprechtii), Oak (Quercus wutaishanica) and Asian White Birch (Betula platyphylla) woodlands, and naturally regenerated mixed forest. Species richness peaked in mixed forests, while pine and oak woodlands harboured discrete communities of intermediate species richness. Oak, pine and mixed forest habitats also showed high levels of species turnover between plots. Canopy closure was an important factor influencing ground beetle assemblages and diversity, and a number of forest specialist species only occurred in pine or oak forests. We believe that some forest specialists have survived earlier deforestation and appear to be supported by new plantation forests, but maintenance of secondary native oak and mixed forests is crucial to safeguard the overall species pool