On the verge? Preferential use of road-facing hedgerow margins by bumblebees in agro-ecosystems

The global pollinator decline is commonly linked to modern intensive farming practices, partly because excessive herbicide and fertilizer use is thought to reduce pollinator food plant availability. This effect is particularly obvious across crop-/non-crop boundaries, but no study has compared pollinator and food plant abundance on adjacent crop- and roadside margins. We compared bumblebee abundance along 30 hedgerows in SW England; bordered either side by roads and arable fields (cultivated with wheat, barley, oilseed rape, or beans). Total bumblebee abundance along roadsides was over twice that observed on adjacent crop-facing margins, irrespective of crop type and this general pattern was apparent for three of the five most common bumblebee species, including generalist and specialist foragers. Both the total number of flowering plant species and the floral abundance of three of the five most visited plants was also higher on roadsides; minor variation between-crops was localised and unrelated to margin orientation. We conclude that organic farming may offer some advantages for pollinator conservation since it reduces field margin exposure to agro-chemical inputs. However, since conventional farming will remain central to global food production, modifications to current practices (such as the use of wildflower strips) are needed and may have ancillary benefits for pollinators by protecting arable margins from disturbance and agro-chemicals. In addition, the fact that the roadsides were demonstrably better habitats for pollinators and their food plants than field-facing margins underscores the widespread suggestion that roadside verges should be utilised more as a conservation tool to promote pollinator biodiversity

Plants and climate change: complexities and surprises.

BACKGROUND: Anthropogenic climate change (ACC) will influence all aspects of plant biology over coming decades. Many changes in wild species have already been well-documented as a result of increased atmospheric CO2 concentrations, warming climate and changing precipitation regimes. A wealth of available data has allowed the use of meta-analyses to examine plant-climate interactions on more sophisticated levels than before. These analyses have revealed major differences in plant response among groups, e.g. with respect to functional traits, taxonomy, life-history and provenance. Interestingly, these meta-analyses have also exposed unexpected mismatches between theory, experimental, and observational studies. SCOPE: We reviewed the literature on species' responses to ACC, finding ∼42 % of 4000 species studied globally are plants (primarily terrestrial). We review impacts on phenology, distributions, ecophysiology, regeneration biology, plant-plant and plant-herbivore interactions, and the roles of plasticity and evolution. We focused on apparent deviations from expectation, and highlighted cases where more sophisticated analyses revealed that unexpected changes were, in fact, responses to ACC. CONCLUSIONS: We found that conventionally expected responses are generally well-understood, and that it is the aberrant responses that are now yielding greater insight into current and possible future impacts of ACC. We argue that inconclusive, unexpected, or counter-intuitive results should be embraced in order to understand apparent disconnects between theory, prediction, and observation. We highlight prime examples from the collection of papers in this Special Issue, as well as general literature. We found use of plant functional groupings/traits had mixed success, but that some underutilized approaches, such as Grime's C/S/R strategies, when incorporated, have improved understanding of observed responses. Despite inherent difficulties, we highlight the need for ecologists to conduct community-level experiments in systems that replicate multiple aspects of ACC. Specifically, we call for development of coordinating experiments across networks of field sites, both natural and man-made

Going native? Flower use by bumblebees in English urban gardens.

BACKGROUND AND AIMS: Although urban gardens provide opportunities for pollinators in an otherwise inhospitable environment, most garden plants are not native to the recipient biogeographical region and their value to local pollinators is disputed. This study tested the hypothesis that bumblebees foraging in English urban gardens preferentially visited sympatric Palaearctic-range plants over species originating outside their native range. METHODS: Twenty-seven surveys of flower availability and bumblebee visitation (Bombus spp.) were conducted over a 3-month summer period. Plants were categorized according to whether they were native British, Palaearctic or non-Palaearctic in origin. A phylogeny of the 119 plant species recorded was constructed and the relationship between floral abundance and the frequency of pollinator visits investigated by means of phylogenetically independent contrasts. Differentiation in utilization of plant species by the five bumblebee species encountered was investigated using niche overlap analyses. KEY RESULTS: There was conflicting evidence for preferential use of native-range Palaearctic plant species by bumblebees depending on which plants were included in the analysis. Evidence was also found for niche partitioning between species based on respective preferences for native and non-native biogeographical range plants. Two bumblebees (Bombus terrestris and B. pratorum) concentrated their foraging activity on non-Palaearctic plants, while two others (B. hortorum and B. pascourum) preferred Palaearctic species. CONCLUSIONS: The long-running debate about the value of native and non-native garden plants to pollinators probably stems from a failure to properly consider biogeographical overlap between plant and pollinator ranges. Gardeners can encourage pollinators without consideration of plant origin or bias towards 'local' biogeographical species. However, dietary specialist bumblebees seem to prefer plants sympatric with their own biogeographical range and, in addition to the cultivation of these species in gardens, provision of native non-horticultural ('weed') species may also be important for pollinator conservation

Bird pollinators, seed storage and cockatoo granivores explain large woody fruits as best seed defense in Hakea

Nutrient-impoverished soils with severe summer drought and frequent fire typify many Mediterranean-type regions of the world. Such conditions limit seed production and restrict opportunities for seedling recruitment making protection from granivores paramount. Our focus was on Hakea, a genus of shrubs widespread in southwestern Australia, whose nutritious seeds are targeted by strong-billed cockatoos. We assessed 56 Hakea species for cockatoo damage in 150 populations spread over 900 km in relation to traits expected to deter avian granivory: dense spiny foliage; large, woody fruits; fruit crypsis via leaf mimicry and shielding; low seed stores; and fruit clustering. We tested hypothesises centred on optimal seed defenses in relation to (a) pollination syndrome (bird vs insect), (b) fire regeneration strategy (killed vs resprouting) and (c) on-plant seed storage (transient vs prolonged).Twenty species in 50 populations showed substantial seed loss from cockatoo granivory. No subregional trends in granivore damage or protective traits were detected, though species in drier, hotter areas were spinier. Species lacking spiny foliage around the fruits (usually bird-pollinated) had much larger (4–5 times) fruits than those with spiny leaves and cryptic fruits (insect-pollinated). Species with woody fruits weighing >1 g were rarely attacked, unlike those with spiny foliage and small cryptic fruits. Fire-killed species were just as resistant to granivores as resprouters but with much greater seed stores. Strongly serotinous species with prolonged seed storage were rarely attacked, with an order of magnitude larger fruits but no difference in seed store compared with weakly/non-serotinous species. Overall, the five traits examined could be ranked in success at preventing seed loss from large woody fruits (most effective), fruit clustering, low seed stores, spinescence, to crypsis (least effective). We conclude that the evolution of large woody fruits is contingent on pollinator type (dictates flower/fruit location, thus apparency to granivores), level of serotiny (response to poor soils and fire that requires prolonged seed defense) and presence of a formidable granivore (that promotes strong defense)

The gathering storm: optimizing management of coastal ecosystems in the face of a climate-driven threat

© The Author(s) 2019. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: [email protected]. BACKGROUND: The combination of rising sea levels and increased likelihood of extreme storm events poses a major threat to our coastlines and as a result, many ecosystems recognized and valued for their important contribution to coastal defence face increased damage from erosion and flooding. Nevertheless, only recently have we begun to examine how plant species and communities, respond to, and recover from, the many disturbances associated with storm events. SCOPE: We review how the threats posed by a combination of sea level rise and storms affects coastal sub-, inter- and supra-tidal plant communities. We consider ecophysiological impacts at the level of the individual plant, but also how ecological interactions at the community level, and responses at landscape scale, inform our understanding of how and why an increasing frequency and intensity of storm damage are vital to effective coastal management. While noting how research is centred on the impact of hurricanes in the US Gulf region, we take a global perspective and consider how ecosystems worldwide (e.g. seagrass, kelp forests, sand dunes, saltmarsh and mangroves) respond to storm damage and contribute to coastal defence. CONCLUSIONS: The threats posed by storms to coastal plant communities are undoubtedly severe, but, beyond this obvious conclusion, we highlight four research priority areas. These call for studies focusing on (1) how storm disturbance affects plant reproduction and recruitment; (2) plant response to the multiple stressors associated with anthropogenic climate change and storm events; (3) the role of ecosystem-level interactions in dictating post-disturbance recovery; and (4) models and long-term monitoring to better predict where and how storms and other climate change-driven phenomena impact coastal ecosystems and services. In so doing, we argue how plant scientists must work with geomorphologists and environmental agencies to protect the unique biodiversity and pivotal contribution to coastal defence delivered by maritime plant communities

Home advantage? Decomposition across the freshwater-estuarine transition zone varies with litter origin and local salinity

Expected increases in the frequency and intensity of storm surges and river flooding may greatly affect the relative salinity of estuarine environments over the coming decades. In this experiment we used detritus from three contrasting environments (marine Fucus vesiculosus; estuarine Spartina anglica; terrestrial Quercus robur) to test the prediction that the decomposition of the different types of litter would be highest in the environment with which they are associated. Patterns of decomposition broadly fitted our prediction: Quercus detritus decomposed more rapidly in freshwater compared with saline conditions while Fucus showed the opposite trend; Spartina showed an intermediate response. Variation in macro-invertebrate assemblages was detected along the salinity gradient but with different patterns between estuaries, suggesting that breakdown rates may be linked in part to local invertebrate assemblages. Nonetheless, our results suggest that perturbation of salinity gradients through climate change could affect the process of litter decomposition and thus alter nutrient cycling in estuarine transition zones. Understanding the vulnerability of estuaries to changes in local abiotic conditions is important given the need to better integrate coastal proceses into a wider management framework at a time when coastlines are increasingly threatened by human activities

Topography-based modulation of environmental factors as a mechanism for intertidal microhabitat formation: A basis for marine ecological design.

Topographic complexity is often considered to be closely associated with habitat complexity and niche diversity; however, complex topography per se does not imply habitat suitability. Rather, ecologically suitable habitats may emerge if topographic features interact with environmental factors and thereby alter their surrounding microenvironment to the benefit of local organisms (e.g., resource provisioning, stress mitigation). Topography may thus act as a key modulator of abiotic stressors and biotic pressures, particularly in environmentally challenging intertidal systems. Here, we review how topography can alter microhabitat conditions with respect to four resources required by intertidal organisms: a source of energy (light, suspended food particles, prey, detritus), water (hydration, buffering of light, temperature and hydrodynamics), shelter (temperature, wave exposure, predation), and habitat space (substratum area, propagule settlement, movement). We synthesize mechanisms and quantitative findings of how environmental factors can be altered through topography and suggest an organism-centered 'form-follows-ecological-function' approach to designing multifunctional marine infrastructure

Occurrence and assemblage composition of intertidal non-native species may be influenced by shipping patterns and artificial structures

Habitat modification coupled with the spread of non-native species (NNS) are among the top threats to marine biodiversity globally. Species are known to be transported to new locations via international shipping and secondarily spread via regional vessels and artificial structures. Rapid Assessment Surveys (RAS) combining quantitative and semi-quantitative methods compared NNS richness and assemblage composition on intertidal natural rocky shores and artificial structures in harbours in different regions along the south coast of England. Quantitative data showed that artificial habitats supported higher richness than natural habitats, while semi-quantitative data found no difference in richness among habitat types. This result was attributed to additional species found in rock pools during searches of complex microhabitats in natural habitats. Assemblages on artificial structures differed among regions, with regions and harbours with greater numbers of vessels supporting greater richness. Results highlight the importance of shipping and artificial structures for NNS introduction and spread