Local adaptation of reproductive performance

Porcelli, D., Gaston, K.J., Butlin, R.K. & Snook, R.R. 2017. Local adaptation of reproductive performance during thermal stress. Journal of Evolutionary Biology, in press. [Image from Shutterstock] shutterstock_137256881

Considerable evidence exists for local adaptation of critical thermal limits in ectotherms following adult temperature stress, but fewer studies have tested for local adaptation of sublethal heat stress effects across life-history stages. In organisms with complex life cycles, such as holometabolous insects, heat stress during juvenile stages may severely impact gametogenesis, having downstream consequences on reproductive performance that may be mediated by local adaptation, although this is rarely studied. Here, we tested how exposure to either benign or heat stress temperature during juvenile and adult stages, either independently or combined, influences egg-to-adult viability, adult sperm motility and fertility in high- and low-latitude populations of Drosophila subobscura. We found both population- and temperature-specific effects on survival and sperm motility; juvenile heat stress decreased survival and subsequent sperm motility and each trait was lower in the northern population. We found an interaction between population and temperature on fertility following application of juvenile heat stress; although fertility was negatively impacted in both populations, the southern population was less affected. When the adult stage was also subject to heat stress, the southern population exhibited positive carry-over effects whereas the northern population’s fertility remained low. Thus, the northern population is more susceptible to sublethal reproductive consequences following exposure to juvenile heat stress. This may be common in other organisms with complex life cycles and current models predicting population responses to climate change, which do not take into account the impact of juvenile heat stress on reproductive performance, may be too conservative.


A dose of gardening

Soga, M., Gaston, K.J. & Yamaura, Y. 2017. Gardening is beneficial for health: a meta-analysis. Preventive Medicine Reports, in press. [Image from Shutterstock] shutterstock_303853934

There is increasing evidence that gardening provides substantial human health benefits. However, no formal statistical assessment has been conducted to test this assertion. Here, we present the results of a meta-analysis of research examining the effects of gardening, including horticultural therapy, on health. We performed a literature search to collect studies that compared health outcomes in control (before participating in gardening or non-gardeners) and treatment groups (after participating in gardening or gardeners) in January 2016. The mean difference in health outcomes between the two groups was calculated for each study, and then the weighted effect size determined both across all and sets of subgroup studies. 22 case studies (published after 2001) were included in the meta-analysis, which comprised 74 comparisons between control and treatment groups. Most studies came from the United States, followed by Europe, Asia, and the Middle East. Studies reported a wide range of health outcomes, such as reductions in depression, anxiety and body mass index, as well as increases in life satisfaction, quality of life and sense of community. Meta analytic estimates showed a significant positive effect of gardening on the health outcomes both for all and sets of subgroup studies, whilst effect sizes differed among eight subgroups. Although Egger’s test indicated the presence of publication bias, significant positive effects of gardening remained after adjusting for this using trim and fill analysis. This study has provided robust evidence for the positive effects of gardening on health. A regular dose of gardening can improve public health.


Tracking garden birds

Cox, D.T.C., Inger, R., Hancock, S., Anderson, K. & Gaston, K.J. 2016. Movement of feeder-using songbirds: the influence of urban features. Scientific Reports 6, 37669. [Image from Shutterstock] shutterstock_240027928

Private gardens provide vital opportunities for people to interact with nature. The most popular form of interaction is through garden bird feeding. Understanding how landscape features and seasons determine patterns of movement of feeder-using songbirds is key to maximising the well-being benefits they provide. To determine these patterns we established three networks of automated data loggers along a gradient of greenspace fragmentation. Over a 12-month period we tracked 452 tagged blue tits Cyantistes caeruleus and great tits Parus major moving between feeder pairs 9,848 times, to address two questions: (i) Do urban features within different forms, and season, influence structural (presence-absence of connections between feeders by birds) and functional (frequency of these connections) connectivity? (ii) Are there general patterns of structural and functional connectivity across forms? Vegetation cover increased connectivity in all three networks, whereas the presence of road gaps negatively affected functional but not structural connectivity. Across networks structural connectivity was lowest in the summer when birds maintain breeding territories, however patterns of functional connectivity appeared to vary with habitat fragmentation. Using empirical data this study shows how key urban features and season influence movement of feeder-using songbirds, and we provide evidence that this is related to greenspace fragmentation.


3D vegetation structure measured from a plane

Hancock, S., Anderson, K., Disney, M. & Gaston, K.J. 2017. Measurement of fine-spatial-resolution 3D vegetation structure with airborne waveform lidar: Calibration and validation with voxelised terrestrial lidar. Remote Sensing of Environment 18, 37-50. screen-shot-2016-11-16-at-12-25-49

Vegetation structure controls habitat availability, ecosystem services, weather, climate and microclimate, but current landscape scale vegetation maps have lacked details of understorey vegetation and within canopy structure at resolutions finer than a few tens of metres. In this paper, a novel signal processing method is used to correctly measure 3D voxelised vegetation cover from full-waveform ALS data at 1.5 m
horizontal and 50 cm vertical resolution, including understorey vegetation and within-canopy structure. A new method for calibrating and validating the instrument specific ALS processing using high resolution TLS data is also presented and used to calibrate and validate the ALS derived data products over a wide range of land cover types within a heterogeneous urban area, including woodland, gardens and streets. This showed the method to accurately retrieve voxelised canopy cover maps with less than 0.4% of voxels containing false negatives, 10% of voxels containing false positives and a canopy cover accuracy within voxels of 24%. The method was applied across 100 km2 and the resulting structure maps were compared to the more widely used discrete return ALS and Gaussian decomposed waveform ALS data products. These products were found to give little information on the within-canopy structure and so are only capable of deriving coarse resolution, plot-scale structure metrics. The detailed 3D canopy maps derived from the new method allow landscape scale ecosystem processes to be examined in more detail than has previously been possible, and the new method reveals details about the canopy understorey, creating opportunities for ecological investigations. The calibration method can be applied to any waveform ALS instrument and processing method. All code used in this paper is freely available online through bitbucket (https://bitbucket.org/StevenHancock/voxel_lidar).


Cooled by plants

Edmondson, J.L., Stott, I., Davies, Z.G., Gaston, K.J. & Leake, J.R. 2016. Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs. Scientific Reports 6, 33708. shutterstock_270038441[Image from Shutterstock]

Urban areas are major contributors to air pollution and climate change, causing impacts on human health that are amplified by the microclimatological effects of buildings and grey infrastructure through the urban heat island (UHI) effect. Urban greenspaces may be important in reducing surface temperature extremes, but their effects have not been investigated at a city-wide scale. Across a midsize UK city we buried temperature loggers at the surface of greenspace soils at 100 sites, stratified by proximity to city centre, vegetation cover and land-use. Mean daily soil surface temperature over 11 months increased by 0.6 °C over the 5 km from the city outskirts to the centre. Trees and shrubs in non-domestic greenspace reduced mean maximum daily soil surface temperatures in the summer by 5.7 °C compared to herbaceous vegetation, but tended to maintain slightly higher temperatures in winter. Trees in domestic gardens, which tend to be smaller, were less effective at reducing summer soil surface temperatures. Our findings reveal that the UHI effects soil temperatures at a city-wide scale, and that in their moderating urban soil surface temperature extremes, trees and shrubs may help to reduce the adverse impacts of urbanization on microclimate, soil processes and human health.


Loss of connection to nature matters

Soga, M., Gaston, K.J., Koyanagi, T.F., Kurisu, K. & Hanaki, K. 2016. Urban residents’ perceptions of neighbourhood nature: does the extinction of experience matter? Biological Conservation 203, 143-150.shutterstock_151363640 [Image from Shutterstock]

Today’s children have less direct contact with nature than ever before, resulting in an “extinction of experience”. Research has suggested that such loss of daily interactions decreases people’s appreciation of the natural world, but this remains quantitatively unexplored. We conducted a questionnaire survey of undergraduate university students in Tokyo, Japan, and determined the effects of frequency of contact with nature on emotional connect- edness to nature and perceptions of neighbourhood nature. A total of 255 students participated in the surveys. Students’ perceptions of neighbourhood nature were measured by to what extent they valued cultural ecosystem services derived from neighbourhood natural environments, birds and butterflies. Results showed that students valued neighbourhood natural environments, birds and butterflies for many different reasons, such as relaxation, beauty of natural scenes, an indicator of seasonality, and opportunities for education. Linear mixed models revealed that both current and childhood frequencies of contact with nature were positively related not only to students’ emotional connectedness to nature but also their perceptions of neighbourhood nature. Students’ emotional connection to nature and perceptions of neighbourhood nature were positively associated with each other. Our results suggest that, given the rapid decrease in children’s daily contact with nature, public appreciation of the value of the natural world is likely gradually also to decrease. This can be a major obstacle to reversing global environmental challenges. People should therefore be encouraged to experience neighbourhood natural environments and biodiversity, and city planners and policy makers will play a vital role in connecting people with nature.


Dining on the dead

Inger, R., Per, E., Cox, D.T.C., Norton, B. & Gaston, K.J. 2017. Role of vertebrate scavengers in urban ecosystems in the UK. Ecology and Evolution, online early. shutterstock_147173099 [Image from Shutterstock]

Recent research has demonstrated how scavenging, the act of consuming dead animals, plays a key role in ecosystem structure, functioning, and stability. A growing number of studies suggest that vertebrate scavengers also provide key ecosystem services, the benefits humans gain from the natural world, particularly in the removal of carcasses from the environment. An increasing proportion of the human population is now residing in cities and towns, many of which, despite being highly altered environments, contain significant wildlife populations, and so animal carcasses. Indeed, non-predation fatalities may be higher within urban than natural environments. Despite this, the fate of carcasses in urban environments and the role vertebrate scavengers play in their removal have not been determined. In this study, we quantify the role of vertebrate scavengers in urban environments in three towns in the UK. Using experimentally deployed rat carcasses and rapid fire motion-triggered cameras, we determined which species were scavenging and how removal of carcass biomass was partitioned between them. Of the 63 experimental carcasses deployed, vertebrate scavenger activity was detected at 67%. There was a significantly greater depletion in carcass biomass in the presence (mean loss of 194 g) than absence (mean loss of 14 g) of scavengers. Scavenger activity was restricted to three species, Carrion crows Corvus corone, Eurasian magpies Pica pica, and European red foxes Vulpes vulpes. From behavioural analysis, we estimated that a maximum of 73% of the carcass biomass was removed by vertebrate scavengers. Despite having low species richness, the urban scavenger community in our urban study system removed a similar proportion of carcasses to those reported in more pristine environments. Vertebrate scavengers are providing a key urban ecosystem service in terms of carcass removal. This service is, however, often overlooked, and the species that provide it are among some of the most disliked and persecuted.


Weeds on the web

Robinson, B.S., Inger, R., Crowley, S.L. & Gaston, K.J. 2016. Weeds on the web: conflicting management advice about invasive non-native plants. Journal of Applied Ecology, online early. shutterstock_149062910 [Image from Shutterstock]

1. Invasive non-native plants (INNPs) can have serious and widespread negative ecological and socio-economic impacts. It is therefore important they are managed appropriately. Within domestic gardens management decisions, which will tend to be made by individual members of the public, are likely to vary depending on (a) understanding of problems caused by INNP, and (b) knowledge of best practice.
2. Using content analysis, an approach seldom employed in an ecological context, this study analysed variation in internet-based information sources regarding INNP to determine how this collective discourse might influence risk perceptions and management decisions for domestic garden owners/managers. We used Japanese knotweed Fallopia japonica in the UK, as a case study, as it is one of the most ecologically and economically damaging INNP in the region. Our analysis categorized the types of author disseminating information about Japanese knotweed, the relative frequency of documents between author categories, and variation in content and style between and within author categories.
3. We identified five author categories: environmental NGOs, control companies, government, media and the property market. There was extensive variation in document structure, topics discussed, references and links to other sources, and language style; sometimes this variation was between author categories and sometimes within author categories. The most significant variation in topics discussed between author categories was indirect socio-economic problems, with control companies discussing these most. The number of pieces of legislation referenced and the proportion of militaristic words used were also highly significantly different between author categories. Some documents used neutral terminology and were more circumspect, whilst others were more forceful in expressing opinions and sensational.
4. The author category returning the highest number of documents was the subcategory local government, the shortest of which contained neither links to other information nor referenced any organizations. Further analysis of local government documents revealed conflicting advice regarding the disposal of Japanese knotweed waste material; confusion about this topic could result in decisions being made that spread Japanese knotweed further and are potentially unlawful.
5. The potential implications of our findings for the management of INNP in domestic gardens and societal perceptions of risks posed by INNP are discussed.
6. Synthesis and applications. To help prevent inappropriate management of invasive nonnative plants (INNPs), for example Japanese knotweed Fallopia japonica in domestic gardens, we recommend that local and national authorities collaborate and work towards disseminating more consistent messages about (a) the potential socio-economic and ecological problems caused by INNP, whilst avoiding hyperbole, and (b) the most appropriate management techniques.


Latitude in gene expression

Porcelli, D., Westram, A.M., Pascual, M., Gaston, K.J., Butlin, R.K. & Snook, R.R. 2017. Gene expression clines reveal local adaptation and associated trade-offs at a continental scale. Scientific Reports 6, 32975.drosophila_subobscura_800 [Image from D. Obbard]

Local adaptation, where fitness in one environment comes at a cost in another, should lead to spatial variation in trade-offs between life history traits and may be critical for population persistence. Recent studies have sought genomic signals of local adaptation, but often have been limited to laboratory populations representing two environmentally different locations of a species’ distribution. We measured gene expression, as a proxy for fitness, in males of Drosophila subobscura, occupying a 20° latitudinal and 11 °C thermal range. Uniquely, we sampled six populations and studied both common garden and semi-natural responses to identify signals of local adaptation. We found contrasting patterns of investment: transcripts with expression positively correlated to latitude were enriched for metabolic processes, expressed across all tissues whereas negatively correlated transcripts were enriched for reproductive processes, expressed primarily in testes. When using only the end populations, to compare our results to previous studies, we found that locally adaptive patterns were obscured. While phenotypic trade-offs between metabolic and reproductive functions across widespread species are well-known, our results identify underlying genetic and tissue responses at a continental scale that may be responsible for this. This may contribute to understanding population persistence under environmental change.


Connection to nature in cities

Shanahan, D.F., Cox, D.T.C, Fuller, R.A., Hancock, S., Lin, B.B., Anderson, K., Bush, R. & Gaston, K.J. (2017) Variation in experiences of nature across gradients of tree cover in compact and sprawling cities. Landscape and Urban Planning 157, 231-238. (Image from Shutterstock) shutterstock_309919712

Urban environments are expanding globally, and by 2050 nearly 70% of the world’s population will live in towns and cities, where opportunities to experience nature are more limited than in rural areas. This transition could have important implications for health and wellbeing given the diversity of benefits that nature delivers. Despite these issues, there is a lack of information on whether or how the experience of nature changes as green space becomes less available. We explore this question for residents of two case study cities of varying urban designs, sprawling (Brisbane, Australia) and compact (three English towns, U.K). Second, we examine how people’s feelings of connection to nature (measured using the Nature Relatedness scale) vary across this same gradient of nature availability. Despite climatic and cultural differences we found substantial similarities between the two locations. Lower levels of neighbourhood tree cover were associated with a reduced frequency of visits to private and public green spaces, and a similar pattern was found for the duration of time spent in private and public green spaces for Brisbane. Residents of both urban areas showed similar levels of nature relatedness, and there was a weak but positive association between tree cover and Nature Relatedness. These results suggest that regardless of the style of urban design, maintaining the availability of nature close to home is a critical step to protect people’s experiences of nature and their desire to seek out those experiences.