Dragonfly mind control?

For those of you not familiar with Cordyceps fungus, that’s the one that attacks insects (and other arthropods) by infecting and then spreading through the whole body. The result is something like what you see below:

Dragonfly with Cordyceps infection (Ophiocordyceps odonatae)

Each one of those little growths is a “fruiting body” and that is where the fungus releases its spores in order to found new patches of fungus. The most famous of these kinds of fungi is perhaps Ophiocordyceps unilateralis, which infects ants and influences their behaviour. The fungus forces an ant to climb a blade of grass or a twig and then attach there until it dies. Meanwhile the fungus produces a series of fruiting bodies that release spores from the new vantage point – the height helps those spores to disperse a greater distance. Apparently fossilised plants from 50m years ago also bear the marks of these Cordyceps-related attachments by insects, suggesting that this is an old battle.

What we don’t know is the extent to which Cordyceps influences the behaviour of other hosts. I posted the image above because it is the first time that I have seen a dragonfly infected in this way. It would make more sense (to me, at least!) for Cordyceps infecting a dragonfly to make it fly upwards while the fruiting bodies are releasing spores to broadcast those offspring as far as possible. However, the only image I have seen is this one where the animal is firmly rooted to the perch.

If it was a parasite that affected dragonfly flight then it wouldn’t be the first. A few recent studies (e.g. Suhonen et al. 2010) have suggested that dragonflies infected with parasitic mites that cling to the outside of the animal result in greater movement. It has been suggested that this could be an attempt to get out of an area with a high parasite population – after all, that’s not a great place to raise your little dragonfly family. However, we think this response has evolved to help the host and not the parasite, which is the opposite to the response elicited by the manipulative Cordyceps.

References

Suhonen, J., Honkavaara, J., Rantala, M.J. (2010) Activation of the immune system promotes insect dispersal in the wild, Oecologia, 162 (3): 541-547.


Image credit: Paul Bertner, https://flic.kr/p/qodUNR, all rights reserved, used with permission.

Ecology and Evolution PhD Opportunities at the University of Leeds

I’m delighted to announce a suite of additional PhD projects in the School of Biology at the University of Leeds (scheme details are here).  These are in addition to the dozen or so competitively-funded projects through our NERC DTP, so please do check there as well if you are interested.  Most titles are indicative of the broad research area, but there will usually be a great deal of flexibility in the nature of the project depending on the interests of the student.  The deadline for all projects is Thursday 29th January 2015, and applicants will need to have submitted a research degree application form (see our “How to apply” page) and be in receipt of a student ID number prior to application for the scheme. Briefly, the titles are:

  • The Evolution of Plant Form
  • Marine microbial processes and interactions
  • Improving piglet survival and subsequent performance
  • Managing soil plant processes to enhance the sustainable intensification of agriculture
  • Emerging Infectious Diseases
  • Continental trends in, and drivers of, the spread of European aquatic invasive species
  • Biomimicry, biophilia, and urban design solutions
  • Identifying and investigating factors which improve sow performance in Irish pig herds

See the project summaries below for more details.Read More »

Do dragonflies give birth to live young?

Heliocypha perforataSomething strange seems to be happening in one particular species of damselfly, the common blue jewel Rhinocypha perforata (pictured right). Or at least it has been caught on video for the first time… Aside from being a particularly attractive species of damselfly found in China, Thailand, Laos, Malaysia and Vietnam, the common blue jewel seems to adopt a rather unusual form of reproduction (for an insect, at least). Read More »

How big is a damselfly, and why?

Calopteryx_maculata_mating_(crop)Background: Body size is among the most important characteristics of animals and plants. Larger animals are capable of buffering against their environment (think big polar bear vs tiny chihuahua in the snow!) so that they can survive in a wider range of locations, are capable of eating a wider range of prey, and consume more prey than smaller animals leading to a stronger impact on ecosystems. However, we are still trying to understand the factors that influence body size, both ecologically and evolutionarily.

What I did: A number of previous studies have compared body size in particular animals across different locations to see whether or not there are consistent patterns in that variability. I wanted to collect specimens of a single species (the ebony jewelwing damselfly, Calopteryx maculata) 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.  I showed that there was a general increase in size further north, but that this was not a simple increase. Instead, there was a U-shaped relationship between latitude and size with larger animals in the south and the north with an intermediate size in the middle. When I looked at the drivers of this trend, it appeared that warm temperatures resulted in higher body sizes in the south. In the north, the animals use shortening days as a signal to accelerate their development and so in the most northern regions animals were developing very quickly despite the cold.

Importance: Large scale (across the whole of an animal’s range) measurements of body size are essential to provide an ecologically relevant test of explanations for changing body size. These findings support previous laboratory work which suggested a twinned role for temperature and photoperiod in driving development in damselflies.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Time stress and temperature explain continental variation in damselfly body size”, was published in the journal Ecography in 2013. You can find this paper at the publisher’s website or for free at Figshare.

Image credit: Kevin Payravi, http://bit.ly/1q7B2Ph, CC BY-SA 3.0

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, http://bit.ly/1xHxpks, 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, 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.