Science

Spotlight

Enhancing road verges to aid pollinator conservation: A review

Benjamin B. Phillipsa,⁎ , Claire Wallaceb , Bethany R. Robertsa , Andrew T. Whitehousec , Kevin J. Gastona , James M. Bullockd , Lynn V. Dicksb,e , Juliet L. Osbornea

Road verges provide habitats that have considerable potential as a tool for pollinator conservation, especially given the significant area of land that they collectively cover. Growing societal interest in managing road verges for pollinators suggests an immediate need for evidence-based management guidance. We used a formal, global literature review to assess evidence for the benefits of road verges for pollinators (as habitats and corridors), the potential negative impacts of roads on pollinators (vehicle-pollinator collisions, pollution, barriers to movement) and how to enhance road verges for pollinators through management. We identified, reviewed and synthesised 140 relevant studies. Overall, the literature review demonstrated that: (i) road verges are often hotspots of flowers and pollinators (well established), (ii) traffic and road pollution can cause mortality and other negative impacts on pollinators (well established), but available evidence suggests that the benefits of road verges to pollinators far outweigh the costs (established but incomplete), and (iii) road verges can be enhanced for pollinators through strategic management (well established). Future research should address the lack of holistic and large-scale understanding of the net effects of road verges on pollinators. We provide management recommendations for enhancing both individual road verges for pollinators (e.g. optimised mowing regimes) and entire road networks (e.g. prioritising enhancement of verges with the greatest capacity to benefit pollinators), and highlight three of the most strongly supported recommendations: (i) creating high quality habitats on new and existing road verges, (ii) reducing mowing frequency to 0–2 cuts/year

Speckled Wood: Wing morphological responses to latitude and colonisation in a range expanding butterfly

Evelyn D. Taylor-Cox1, Callum J. Macgregor2,3, Amy Corthine1, Jane K. Hill2, Jenny A. Hodgson1, Ilik J. Saccheri1

A study of how the Speckled Wood butterfly has been able to achieve such a rapid expansion and what we can learn from this as climate change bites . Are northerners bigger and darker? Anecdotal evidence from our recorders suggests they are and has been assisted in its invasion even into our gardens by the trend towards wet warm summers and lush grass growth. This species swept through Yorkshire in the 1980's to become one of our most familiar butterflies not only common anywhere shady but by being on the wing almost continuously from April till October.

The map shows the distribution of P. aegeria and the pattern of range expansion from 1965–2017. Colours show years when P. aegeria was first recorded at a 10 km grid resolution. Crosses indicate site locations sampled for the study

This study documents detailed wing morphological variation (size, shape and colour) in the Speckled Wood butterfly, P. aegeria, across two recently expanded populations in mainland Britain, suggesting differing responses to environmental and demographic factors. The size of P. aegeria increases with latitude, consistent with Bergmann’s rule, and during the range expansion process, with more recently colonised populations being larger than core populations. Shape changes, independent of size, are most strongly associated with colonisation history. Forewing shape becomes more rounded, whereas hindwing shape becomes longer, in more recently colonised populations and with latitude. The distribution of average lightness (opposite of melanism) is more strongly associated with temperature during development than it is to latitude, and runs contrary to the traditional thermal melanism hypothesis. Furthermore, the area of brown relative to cream increases with latitude, but not enough to overcome the general lightening in both areas. Finally, the contrast between brown and cream areas increases with latitude, accounting for the human perception that individuals become darker further north. Overall, this study sheds light on the interaction of temperature-sensitive plastic traits and selection during a mainly climate-driven range expansion.

" Populations undergoing rapid climate-driven range expansion experience distinct selection regimes dominated both by increased dispersal at the leading edges and steep environmental gradients. Characterisation of traits associated with such expansions provides insight into the selection pressures and evolutionary constraints that shape demographic and evolutionary responses. Here we investigate patterns in three components of wing morphology (size, shape, colour) often linked to dispersal ability and thermoregulation, along latitudinal gradients of range expansion in the Speckled Wood butterfly (Pararge aegeria) in Britain "

Resolving a 150 year old argument: Why do male and female butterflies differ in colour?

Males and females of many species are dimorphic; there are differences in the way the sexes look and function. One of the most studied types of dimorphism is dichromatism, where males and females have different colors.

It is often assumed that sexual selection is important to dichromatism, as choosy females often mate with colorful males. At the same time, natural selection by predators against elaborated colors can especially be strong for females, as they may need to carry eggs or provide maternal care making them more vulnerable.

For as long as we have known about natural and sexual selection, however, it has been debated which of these two forces initially creates dichromatism.

Charles Darwin argued that sexual selection drives male color away from female color, whereas contemporary Alfred Russel Wallace instead thought that natural selection pulled female color away from the male's.

Here, we revisit this debate using butterflies, one of the taxa Darwin and Wallace argued over, to determine whether Darwin's or Wallace's model is more important in the evolution of dichromatism.

We used drawings from a field guide to quantify the color difference between males and females of all European non‐hesperiid butterfly species, and modeled how their colors have evolved over time.

We show that the color of males generally evolves faster than that of females.

By using the direction of male and female color evolution along the phylogeny, we also determined that changes in male color are around twice as important to dichromatism evolution than changes in female color.

These results show that directional selection on males, likely due to sexual selection, is the main driver of dichromatism in butterflies.

This supports Darwin's, but not Wallace's, model of dichromatism evolution, resolving a 150‐year‐old argument.

more here

(Summary Extract )

Opposite: Colour profiles of Male and Females

Bucking the trend - Why are some British moths on the rise?


Online talk with Douglas Boyes, Newcastle University ; one of our young scientists


Recently, there has been a surge of interest in insect declines, with several high-profile studies generating extensive media coverage (‘insectageddon’). However, not all insects are declining. Conservation scientists have understandably focused on decreasing species, though these only provide half the story of biodiversity change. Appreciating how some species are thriving despite unprecedented anthropogenic pressures could provide insights for mitigating wider declines. The talk is based on Douglas Boyes’s MSc project which examined changes in the prevalence of 51 moth species, using two national datasets. The ‘winners’ are diverse, including long-term residents, habitat specialists, and recent colonists. The causes of these trends are poorly understood. Whilst climate change is considered an important driver, the success of many ‘winners’ likely arises from numerous, intertwining factors.

Douglas has been recording moths since aged 12, finding over 800 species in his garden. He further developed his passion for moths at the University of Oxford, through undergraduate and postgraduate research. Douglas is currently undertaking a PhD at the UK Centre for Ecology & Hydrology. This investigates the impacts of light pollution on moths.

Watch here.

Provide shady spots to protect butterflies from climate change, say scientists at Cambridge + Lancaster

Researchers have discovered significant variations in the ability of different UK butterfly species to maintain a suitable body temperature. Species that rely most on finding a suitably shady location to keep cool are at the greatest risk of population decline. The results predict how climate change might impact butterfly communities, and will inform conservation strategies to protect them.

The results, published today in the Journal of Animal Ecology, show that larger and paler butterflies including the Large White (Pieris brassicae) and Brimstone (Gonepteryx rhamni) are best able to buffer themselves against environmental temperature swings. They angle their large, reflective wings in relation to the sun, and use them to direct the sun's heat either away from, or onto their bodies. These species have either stable or growing populations.

More colourful larger species such as the Peacock (Aglais io) and Red Admiral (Vanessa atalanta) have greater difficulty controlling their body temperature, but even they are better than their smaller relatives like the Small Heath (Coenonympha pamphilus).

The study found that some butterfly species rely on finding a spot at a specific temperature within a landscape -- termed a 'microclimate' -- to control their body temperature. Air temperatures vary on a fine scale: a shaded patch of ground is cooler than one in full sun, for example. These 'thermal specialists', including Brown Argus (Aricia agestis) and Small Copper (Lycaena phlaeas), have suffered larger population declines over the last 40 years.

All butterflies are ectotherms: they can't generate their own body heat. "Butterfly species that aren't very good at controlling their temperature with small behavioural changes, but rely on choosing a micro-habitat at the right temperature, are likely to suffer the most from climate change and habitat loss," said Dr Andrew Bladon, a Postdoctoral Research Associate in the University of Cambridge's Department of Zoology, and first author of the report.

He added: "We need to make landscapes more diverse to help conserve many of our butterfly species. Even within a garden lawn, patches of grass can be left to grow longer -- these areas will provide cooler, shady places for many species of butterfly. In nature reserves, some areas could be grazed or cut and others left standing. We also need to protect features that break up the monotony of farm landscapes, like hedgerows, ditches, and patches of woodland."

Landscapes with a diversity of heights and features have a greater range of temperatures than flat, monotonous ones. This applies on scales from kilometres to centimetres: from hillsides to flower patches. Such structural diversity creates different microclimates that many butterflies use to regulate their temperature.

The research involved catching nearly 4,000 wild butterflies in hand-held nets, and taking the temperature of each using a fine probe. The surrounding air temperature was measured, and for butterflies found perching on a plant, the air temperature at the perch was also taken. This indicated the degree to which butterflies were seeking out specific locations to control their body temperature. In total, 29 different butterfly species were recorded.

The study reveals that butterflies are either thermal generalists or thermal specialists, and this does not always correspond with their current categorisations as either habitat generalists or specialists.

"As we plan conservation measures to address the effects of climate change, it will be important to understand not only the habitat requirements of different butterfly species, but also their temperature requirements," said Dr Ed Turner in the University Museum of Zoology, Cambridge, who led the work.

He added: "With this new understanding of butterflies, we should be able to better manage habitats and landscapes to protect them, and in doing so we're probably also protecting other insects too."

Over the past thirty years, many species of butterfly have expanded their range northwards, as more northerly places have become warmer due to climate change. The ranges of species adapted to cooler environments are shrinking. These trends have been tracked for butterfly populations as a whole, but no previous study has investigated how the individual butterflies that make up these populations are able to respond to small scale temperature changes.

Full article here