More toxic frogs live longer, but more venomous snakes do not

frog-284044_1280Background: It is thought that all animals age: they show an increased probability of death at greater ages. However, the lifespans of many animals vary widely. What is it that determines whether or not an animal lives for one year or one hundred years? One of the key drivers is thought to be how likely you are to be killed by something else. Those animals that that are unlikely to be eaten, whether that is because they are very large (elephants), well armoured (tortoises) or poisonous (poison dart frogs), tend to evolve lower rates of ageing. After all, if you are going to live for a long time anyway, you might as well make the most of it. On the other hand, if you live precariously from day to day then there isn’t much point in investing later in life because you probably won’t get that far.

What we did: We compared lifespans of amphibians and snakes that either had a chemical defense (in amphibians) or venom (in snakes) with those that did not have those traits. We showed that (accounting for their evolutionary history) poisonous amphibians had a significantly longer lifespan than non-poisonous amphibians, but there was no difference in venomous and non-venomous snakes.

Importance: This study has two major implications. The first is that it is vital to incorporate evolutionary history into these sorts of analyses. We had built our study on the findings of an earlier piece of work (which did not account for evolutionary history) that suggested that the snakes also showed a longer lifespan when they were venomous, but our results refute that earlier finding. Second, our findings offer yet more evidence for an offensive role for the origins of snake venom, which has been suggested in other recent studies.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Species with a chemical defense, but not chemical offense, live longer”, was published in the Journal of Evolutionary Biology in 2013. You can find this paper at the publisher or for free at Figshare.

Image credit: Ephraimstochter,, Public Domain.

One simple way to increase visibility of your scientific publications

Background: As well as publishing in ecology and evolutionary biology, I am also interested in how that publishing industry works. There is a clear need to disseminate information as widely as possible in order to accelerate the rate of testing of new theories and discovery of new information. However, some publishing models (and some publishing companies) hide scientific research away so that most people do not have access to that work. Self-archiving is a way for researchers to make available certain forms of their research without breaking copyright (which is almost always handed over to the publishers).

What I did: I reviewed some of the literature on the benefits of self-archiving, in terms of the access to the general public and what has become known as the “open access advantage”: papers that are more openly available are cited more. I also show that over half of all ecology and evolution papers could have been archived in a format that was almost identical to their final, finished format without breaking copyright. I then highlight key methods that researchers can use to self-archive their work: publishing through institutional repositories, third party websites, or self-creation of online portfolios using online tools.

Importance: Self-archiving has the potential to open up research (often funded by taxpayers) to a far wider audience, and this is an important step towards making research more accessible to the general public.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled ““Going green”: self-archiving as a means for dissemination of research output in ecology and evolution”, was published in the journal Ideas in Ecology and Evolution in 2013. You can find this paper for free at the publisher.

The psychology of animal camouflage

DisruptiveColourationBackground: There are a number of ways in which animals and plants attempt to defend themselves from predators. Sometimes they look or sound like something that they are not, such as another animal or plant that is venomous, in a process known as “mimicry”. Other times, rather than attempting to deceive a predator after being seen, the animal or plant might try to hide altogether. This second defensive strategy, known as “camouflage”, can take a number of forms. One of the most interesting forms of camouflage is “disruptive colouration” which involves breaking up the edge of an animal to make it harder to detect.

What we did: Rich Webster is a PhD student at Carleton University who applied a novel approach to the question of how disruptive colouration helps to hide animals. He used eye-tracking technology with humans as predators searching for digital moths on pictures of trees. With this approach he was able to see where people were looking and how long it really took them to find the “moth”. Importantly, he could also tell how many times they looked at the moth without actually seeing it. We were able to show that the length of time taken to find a target and the number of times that the target was missed were both significantly higher when the moth had a larger number of patches on the edge of its wings.

Importance: Mottled colouration has been observed in many species, but until now we have not had a clear description of the mechanism by which this form of defensive colouration acts. Our results provide that first insight into how and why predators sometimes fail to find prey which are camouflaged in this way.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Disruptive camouflage impairs object recognition”, was published in the journal Biology Letters in 2013. You can find this paper at the publisher or archived at Figshare.

Image credit: All images are by Rich Webster, and used with permission.

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,, 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,, 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,, 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,

Online computer programming courses

Computer programming is becoming an increasingly important part of biology (my own discipline) and a range of other subjects.  Programming allows the analysis of data, the creation of software and the building of online resources and interfaces.  There are a range of online courses that you can take to develop these skills, and use as teaching aids for students, that cover a lot of different languages with different applications:


Codeschool offers four key “paths” composed of sets of modules in different programming environments: Ruby and JavaScript (two different methods for online application building), HTML/CSS (web design), and iOS (for Apple apps).  However, they also offer “electives” alongside the main paths, looking at R (an open source programming language), Git (a method for version control in the development of programming), and Chrome Developer Tools (for apps in the Chrome browser).


Codecademy, much like Codeschool, offers a wide range of programming languages. However, all courses through Codecademy are free of charge.  The focus is on web programming using HTML, CSS and JavaScript, and application building using Ruby, APIs, and Python.  Codecademy also allows people to generate their own courses, meaning that there are many smaller sets of tutorials designed to teach specific principles.

An Example of Use
CodeSchool runs a course called “Try R“, which offers a few hours of interactive training in the R environment.  For those of you not familiar with theR language, R is an open source programming language that is mostly built around data manipulation and analysis.  The course itself loads within the website, with a simulated R environment within which the student can work.  The content covered includes: syntax, vectors, matrices, summary statistics, factors, data frames, and “working with real-world data”.  At Leeds we teach our MSc Biodiversity and Conservation students in R for a short period, but this is the kind of tool that the students can use to familiarise themselves more completely with the language.  It could also be a gentle introduction to some of the R-based MOOCs that are run by Coursera.