Invasive damselflies get bigger as they move through the UK

Exif_JPEG_PICTUREBackground: A large number of species are expanding their ranges in response to climate change. This is also true in the damselflies, where the small red-eyed damselfly (Erythromma viridulum) has recently (around 1998) crossed the sea from France to England.  Since then, the species has moved hundreds of kilometres north in an unprecedented range expansion (at least as far as European dragonflies and damselflies are concerned). What is less clear is what impact this expansion has had on the species. Are the newly-founded populations the same as those that are resident in France? Can we trace the arrival and expansion of the species through genetic techniques?

What we did: Simon Keat was a PhD student at the University of Liverpool who was lucky enough to be just beginning his PhD when the small red-eyed damselfly first established in the UK.  Simon surveyed a number of populations around Europe and in the UK, collecting animals to measure them and extract DNA. With the body size measurements we showed that animals tend to show a strong relationship with latitude: populations further north were much larger and this held for both the older populations in France, Belgium and Germany as well as the newer populations in the UK. Looking at the genetics, we had expected to see declining genetic diversity further north, as a small number of individuals led the charge up the country. However, instead of a decline in diversity in the UK we saw an almost complete lack of genetic pattern.  This suggests that the animals were moving in such great numbers that there was not the time for any local patterns to develop.

Importance: Range expansions have important consequences for many aspects of human life: agricultural pests shift and threaten crops, diseases and their vectors shift and threaten human health, and endangered species shift and potentially move out of protected areas. We have shown that during this particular range expansion there has been negligible change in genetic structure but that newly-invaded areas contain relatively large damselflies.  Since damselflies are voracious predators, this could have substantial implications of local ecosystems.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Bergmann’s rule is maintained during a rapid range expansion in a damselfly”, was published in the journal Global Change Biology in 2014. You can find this paper at the publisher or archived at figshare.

Image credit: Quartl, http://bit.ly/1uX3BOA, CC BY-SA 3.0.

Some hoverflies look like stinging wasps and bees – some even act the part!

Picture1Background: Animals and plants can benefit by resembling other species. For example, some plants have spots that look like ants to deter herbivores, cuckoos look like hawks to frighten smaller birds from their nests, and harmless snakes have striped bodies that resemble highly venomous species. However, there are other modes of resemblance: animals and plants can smell, sound or act like another species in addition to (or instead of) having visual resemblance. However, we don’t know much about how different types of mimicry interact in the wild.

What we did: Heather Penney, a MSc student at Carleton University, collected individuals from 57 species of hoverfly. Hoverflies are famous for having some examples of very close visual mimicry of stinging wasps and bees, but in some species this mimicry is “imperfect”. It is also known that hoverflies can exhibit behaviours that are characteristic of wasps and bees, and so Heather tried to elicit these responses from each of the species that she caught. She found that only 6 out of 57 species exhibited behavioural mimicry, and that these species belonged to only two genera (i.e. they were all closely related). Furthermore, there was some evidence that only animals that looked a lot like wasps also had behavioural mimicry.

Importance: While behavioural mimicry has been described a number of times in the wild, it is rarely surveyed using such a comprehensive approach – Heather tested every species in a community so that we know that there are a range of species that do not exhibit these behaviours. Also, we show that the behaviours are constrained to relatively few high quality visual mimics which suggests that behavioural mimicry acts to enhance morphological mimicry where that morphological mimicry already exists.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “The relationship between morphological and behavioral mimicry in hover flies (Diptera: Syrphidae)”, was published in the journal American Naturalist in 2014. You can find this paper on the publisher’s website or for free at Figshare.

Image credit: Photos by Brent Lamborn, used with permission.

How helpful are urban ponds for biodiversity?

pond-84855_1280Background: Urban ecosystems are becoming increasingly important as areas for biodiversity conservation, as we begin to recognise the importance of preserving natural habitat within heavily modified environments for both wildlife and human well being. Urban ponds are a key part of this network of habitats within cities, and are commonly found in parks, gardens and industrial estates. In fact, there are an estimated 2.5-3.5 million garden ponds in the UK alone, which could have an area the size of Lake Windermere!

What we did: I was invited to submit a review of the biodiversity value of urban ponds. This later expanding beyond simply describing biodiversity patterns to include the ecological processes that generate those patterns. I describe a wide-ranging set of potential negative impacts on urban pond biodiversity, including invasive species, mismanagement, pollution, and habitat destruction.  However, I also took great care to highlight the benefits of these habitats in terms of their use in controlling stormwater, their role in local aesthetics, and the way in which they provide access to nature in inner cities. These ponds can be a fantastic resource if managed well.

Importance: Research on urban water bodies has been growing, and this review highlights both the work that has been done up to now and the gaps in our current knowledge that should be filled in the future.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “The ecology and biodiversity of urban ponds”, was published in the journal WIREs Water in 2014. You can find this paper at the publisher’s website or for free at Figshare.

Image credit: noitulos, http://bit.ly/1C0x7cA, Public Domain.

Damselflies change the colour of their wings when other species are around

Calopteryx maculata M (Four Mile Creek)Background:  Animals and plants have a wide range of colours, and these different colours play different roles in different species. Some species might be signalling to potential predators that they are toxic (like a wasp’s stripes), others might be trying to hide (like a moth’s speckled grey wings), and others might be trying to signal to the opposite sex that they are high quality mates (like a peacock’s train). However, while there are clear functions in principle, the relative importance of different signals might vary depending on the context within which the animal or plant finds itself.  For example, male ebony jewelwing damselflies (Calopteryx maculata) have very dark wings and this is thought to allow females of the same species to choose appropriate mates (i.e. to avoid mating with the wrong species). However, the dark pigment can also play a role in temperature regulation. Damselflies cannot generate their own heat and so rely on absorbing heat from the sun, which is helped by the dark pigment. I was interested in how the darkness of the wings varied between locations which experience different temperatures.

What I did: I wanted to collect specimens of this species for analysis from across its entire range in North America, but the range is so large (Florida to Ontario, and New York to Nebraska) that I wouldn’t have been able to travel to sufficient sites within the one season that I have available.  Instead, I asked a lot of local dragonfly enthusiasts to catch and send me specimens from their local sites. I am extremely grateful to all of them for helping, as this could not have been done without their kind volunteering of time and energy.  I ended up with a substantial dataset of animals from 49 sites across the range. The wings of the animals were clipped from the bodies and scanned using a flatbed scanner, and then the amount of pigment was calculated from the image. I showed that the amount of pigment was pretty constant across the range apart from when the species was found with a similar species: the river jewelwing damselfly (Calopteryx aequabilis). This suggests that there might be an optimal level of pigmentation that is independent of temperature, but that if females start to struggle to identify males of their own species there might be an advantage to changing the levels of pigment.

Importance: There have been a lot of local experiments on the benefits and costs of pigment in animals (including damselflies) but there have been far fewer studies that have looked at large scale patterns in pigmentation.  These sorts of studies are essential to describe biological phenomena in the field and to reveal initial patterns in nature that might indicate interesting or novel evolutionary processes.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Continental variation in wing pigmentation in Calopteryx damselflies is related to the presence of heterospecifics”, was published in the journal PeerJ in 2014. You can find this paper for free at the publisher.

Image credit: That’s one of mine!

Rain, not temperature, seems to have driven fossil mammal diversity in North America

skeletons-268954_1280Background: One of the fundamental questions in ecology is “what drives changes in the numbers of species in time and space?” We can look around us today and see that there are generally many more species in the tropics than nearer the poles. However, another way in which we can look around ourselves is to delve into the fossil record to look back in time. Dani Fraser is a PhD student at Carleton University working on large-scale patterns in fossil mammal biodiversity. Dani was interested in looking at spatial patterns and how they changed through time, but rather than just calculating the number of animals living in each area at each time, we looked at the rate at which the communities changed as we moved further north. The idea is that when climates are relatively stable and warm there is little variability in climate and so there is gradual change in species as you move north. However, as the climate becomes more polarised (i.e. colder at the pole relative to the tropics) the rate of change in animal communities becomes more pronounced.

What we did: We looked at extinct mammals in North America during the Cenozoic (36 million years to the present) and showed that there was greater variability in species between regions when mean annual precipitation was lowest. This is consistent with theory, which suggests that when precipitation is (on average) higher communities are more similar to one another as you move north. We then looked at what might be expected from current mammal species under climate change. We used climate models to predict where these species might occur in the future and saw little evidence of the precipitation relationships that we found in the fossil data.

Importance: Much of the work done on biological responses to climate change has focused on temperature, looking at the number of species in each area, and purely ecological responses (i.e. over short time periods). We demonstrate that precipitation can also play an important role in driving responses to global climate. We also show that it isn’t just the number of species that changes in space but the relationship between communities: there is a greater rate of turnover (a greater dissimilarity) in communities as well. Finally, we show that these relationships seem to be present in the evolutionary record but cannot be predicted from the ecological responses of current mammals, suggesting that the patterns we saw in the fossil record are due (at least in part) to evolutionary processes that are not incorporated into climate models.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Mean annual precipitation explains spatiotemporal patterns of Cenozoic mammal beta diversity and latitudinal diversity gradients in North America”, was published in the journal PLOS ONE in 2014. You can find this paper for free at the publisher’s website.

Image credit: 134213, http://bit.ly/1C0v0Fy, Public Domain.

Bradford’s ponds aren’t reaching their potential, and we think we know why

central-park-143473_1280Background:  When we build ponds in urban areas, they can play a number of important roles: managing floodwater, cooling the urban environment, removing pollution, improving the appearance of built-up areas and providing a habitat for wildlife. However, these different functions often require different forms of management, and so urban managers typically prioritise one or a small number of purposes. We were interested in the biodiversity value of ponds in Bradford in the UK.

What we did: My MSc student, Andrew Noble, surveyed a series of 21 sites across Bradford including 11 ponds that were prioritised for biodiversity, 6 ponds that were prioritised for amenity (usually park lakes and other ornamental features), and 4 ponds that were used as overflow ponds for water management. He surveyed aquatic plants and aquatic invertebrates to investigate patterns of biodiversity. This was then compared against what would be expected from high quality ponds of similar size (called a “reference site approach”). The results showed that the urban ponds were generally of very low quality, and that unsurprisingly the biodiversity ponds tended to contain higher numbers of animals and plants. However, this was not always the case and some amenity and overflow ponds contained more species despite not being managed for biodiversity. Finally, Andrew talked with managers who, while obviously enthusiastic about biodiversity, were unaware of important local factors that were influencing their sites, such as run-off from local sports fields which were likely contributing to algal blooms.

Importance: There have been a range of studies (including some by me) which have suggested that urban ponds can provide substantial benefits for biodiversity. However, these high value ponds are relatively rare, and it is important that we understand what factors result in some ponds being of high value while others are not. This study suggests that management could play a major role.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Poor ecological quality of urban ponds in northern England: causes and consequences”, was published in the journal Urban Ecosystems in 2014. You can find this paper at the publisher’s website.

Image credit: tpsdave, http://bit.ly/11ozTHF, Public Domain.

Urban ponds can contain as many species as ponds outside of cities

UrbanPondBackground:  The management of water in urban areas can be a problem, because rainfall rapidly runs off impervious surfaces like pavements and roads. This means the water quickly enters rivers and streams, which then flood. City managers reduce the rate at which water enters rivers using stormwater management facilities, which often include ponds to hold back the stormwater. These ponds are usually managed just for water retention, but they could potentially form a very useful habitat for aquatic plants and animals in cities.

What we did: We looked at 20 of these stormwater management ponds (SMPs) to see how many animals and plants were using them. We also compared those 20 ponds against 10 other ponds that were not used for stormwater management, but were found in roughly the same area. We showed that the water chemistry in the SMPs was often high in salt, and that the amount of salt in the ponds was related to the amount of urban land cover (which makes sense: much of the salt would have been road salt washed in during snow melt). However, despite some differences in water chemistry there were no significant differences between the SMPs and the other ponds in the diversity of animals. We conclude that it is not the management, per se, that affects the ponds, but the landscape within which they are found.

Importance: Management of particular habitats frequently has to prioritise one function over another. Stormwater management is a major concern in many areas, and so there may not be much willingness to detract from the role of ponds in managing run-off in order to benefit biodiversity. We showed that this may not be necessary: if the ponds are in a relatively low-intensity urban area then they may contain high biodiversity regardless of management.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Stormwater ponds can contain comparable biodiversity to unmanaged wetlands in urban areas”, was published in the journal Hydrobiologia in 2014. You can find this paper at the publisher’s website.

Image credit: tpsdave, http://bit.ly/1rb1IKi, Public Domain.

Damselfly wings change shape in harsher habitats

Background: Odonata (dragonflies and damselflies) are an ancient order of insects. By this, I mean that they have remained largely unchanged since their ancestors evolved 500 million years ago.  They have a fairly unique flight style which is a product of the configuration and use of their wings. Wing length has been used as a measure of odonate body size for many years, but wing shape has received less attention.

What we did: I was interested in whether wing shape varied with latitude in the UK.  The populations living in habitat in the UK are exposed to a range of temperatures depending on location and it might be that certain wing shapes confer advantages in certain habitats. Based on a survey of seven populations of Coenagrion puella, I compared wing shape using a method called “geometric morphometrics”.  This allowed me to look at shape independently of the size of the wing.  I found that the wing shape in the majority of populations was very similar.  All populations in the south of England were comparable, but the populations in the south of Scotland showed a progressive shift away from this “typical” wing shape until a site near Edinburgh which was significantly (if subtly) different.

Importance: Wing shape has been highly conserved throughout odonate evolution (i.e. ancient odonates are similar in shape to present-day odonates). Because even small variations between species are consistent, wing shape and patterns of wing veins have been used to identify species. My study showed that these wing shapes were not as consistent as people had previously thought and that there might be ecological or evolutionary processes that can cause significant variation.


This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Wings of Coenagrion puella vary in shape at the northern range margin (Odonata: Coenagrionidae)”, was published in the International Journal of Odonatology in 2008. You can find this paper online at the publisher, or on Figshare.

Image credit: Lauri, CC BY-NC-SA 2.0, http://bit.ly/1zicIZC

The impact of environmental warming on Odonata – a review [paper summary]

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “The impact of environmental warming on Odonata – a review”, was published in the International Journal of Odonatology in 2012. You can find this paper online at the publisher, or on Figshare.

Background: Odonata (dragonflies and damselflies) are thought to have evolved in the tropics and possess a number of adaptations that allow them to exist at higher latitudes.  This makes them interesting to investigate in the context of climate change, since these adaptations might facilitate a response to increasing temperatures.

What we did: This paper is a review of the literature looking at the ecology and evolution of Odonata in the context of climate change.  A number of areas are discussed including distributional changes, phenological shifts, evolutionary responses, the effects of drought and the physiological effects of temperature.

Importance: A large amount of work has been carried out on the influence of temperature on the biology of Odonata over the past 50-60 years.  This has come from a variety of loosely-related fields and our review brings this together to provide an overview of the state-of-play concerning our understanding of the topic.


Image credit: Patricia H Schuette, CC BY-NC-ND 2.0, http://bit.ly/1BO5i4r

Damselflies change shape under climate change, only if they are close to their limits

Background: A species’ shape and size can tell you a lot about how the animals are doing in their environment.  For example, species tend to get larger at cooler temperatures, a phenomenon known as “Bergmann’s rule”, and they tend to have greater dispersal traits where they need to move further (such as locations where habitat patches are further apart).

What we did: I was interested in shape and size varied between a species that is not moving north under climate change (Pyrrhosoma nymphula, shown above) and a species that has been expanding its range into Scotland (Coenagrion puella). I collected animals at a series of sites from southern England to Scotland for both species.  The results showed that there was little consistent variation in size or dispersal traits in P. nymphula but that C. puella showed increases in size and the relative investment in the thorax and abdomen (indicative of greater flight ability).  These results, taken together, suggest that there has been selection for dispersal traits in the expanding C. puella.

Importance: The presence of traits that could facilitate response to climate change, such as enhanced dispersal to increase colonisation of new habitats, could make the difference between a species thriving or failing under climate change.  This is particularly important for species that rely on aquatic habitats for their life cycle, because water resources are predicted to be under increasing threat in the future.


This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Latitudinal variation in morphology in two damselfly species with contrasting range dynamics”, was published in the European Journal of Entomology in 2008. You can find this paper for free online at the publisher.

Image credit: Thomas Bresson, CC BY 2.0, http://bit.ly/1p25AAC