Tag: evolution

Damselfly sex doesn’t always produce children, and that’s a problem for evolutionary biologists!

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Background:  At the core of ecology and evolutionary biology is the concept of “fitness”, broadly defined as the number of copies of an animal’s genes it manages to leave in subsequent generations. However, biologist rarely measure this genetic fitness.  Instead, we use proxies such as the number of times an animal mated or the number of eggs an animal laid. Sometimes, we use proxies that are even further removed, such as body size (under the assumption that larger females lay more eggs).

What we did: This study compared two traditional forms of fitness measurement, daily mating rate and lifetime mating success, with a genetic measure of fitness based on finding the number of offspring each individual produced in the next generation.  We monitored a single, isolated pond over two years and individually identified all damselflies of the species Coenagrion puella, the azure damselfly.  Each individual also had a genetic sample taken and we used genetic markers called “microsatellites” to identify each individual.  When we came back the next year, we did the same thing.  This species goes through one generation per year so we knew that all the animals in the second year were the offspring of those in the first.  By comparing the genetics of the potential parents with those of the potential offspring we were able to assign offspring to parents to produce a much more accurate picture of this concept of “fitness”.  Unfortunately, what we found was that our behavioural measurements did not reflect this more accurate measure of fitness.

Importance: Since the concept of fitness is so important to evolutionary biology, it is important to test the assumptions of the studies that have sought to measure it.  We have demonstrated that some of those previous studies were not using particularly reliable proxies for fitness.  However, we have provided a case study of a potential method for avoiding these problems: by directly genotyping and assigning parents to offspring in the field we can get a much clearer picture of what “fitness” really means.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Field estimates of reproductive success in a model insect: behavioural surrogates are poor predictors of fitness”, was published in the journal Ecology Letters in 2011. You can find this paper online at the publisher, or on Figshare.

Image credit: One of mine, CC-BY 3.0

Less common species tend to have more parasites

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Background:  Parasites and the individuals that they attack (called “hosts”) often have a long evolutionary history of interaction. This history often plays-out as an “arms race” where the parasite finds a new way of attacking the host and the host then evolves a defence against that attack, followed by subsequent evolution by the parasite. Not only this, but species of parasites (such as the aquatic mites and protozoa that I work on) that exploit many host species can differentially affect those different hosts. In this study, we were interested in how parasitic protozoa affect closely related damselfly species that differed in their distributions.

What we did: Julia Mlynarek, a PhD student at Carleton University, collected a large number of damselflies from a number of sites around eastern Ontario. The species were grouped into pairs so that we could compare between species from the same genus.  She dissected these to find the number of protozoa (like the one shown above) in guts of each animal. We found that species with smaller geographical distributions tended to have more protozoan parasites than closely related species with larger distributions.

Importance: Explaining how parasites affect their hosts is a big question spanning ecology and evolutionary biology. These results suggest that there might be a combined effect of (i) shared parasites due to evolutionary history, and (ii) varying resistance due to different exposure across geographical ranges.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Higher gregarine parasitism often in sibling species of host damselflies with smaller geographical distributions”, was published in the journal Ecological Entomology in 2012. You can find this paper online at the publisher, or on Figshare.

Image credit: Christophe Laumer, CC BY 2.0, http://bit.ly/1rrvyzt

PhD opportunities in ecology and evolution

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As part of the new NERC Doctoral Training Program at the University of Leeds, I have two PhD projects to advertise that are now (as of 15th November 2013) open to applicants:

1: DragonFlight: Linking the mechanics and energetics of flight to conservation status and responses to climate change in dragonflies

dragonfly-177338_1280The DragonFlight project builds on my earlier interests in dragonfly dispersal (1), macroecology (2), and flight morphology (3).  There has quite a bit of work done on the flight of dragonflies, but much of this has taken place in the laboratory and has not considered what goes on in the field.  Similarly, there has been quite a lot of landscape-scale work done in the form of mark-recapture studies or analyses of historical records (including my own), but none of this has really tested for the traits that underlie flight ability.  This project will link detailed biomechanical measurements of dragonfly flight to our knowledge of responses to climate change (i.e. range shifts) or conservation status.

2: Teaching old beetles new tricks: applying novel genetic techniques to re-establish a classic ecological model system, Tribolium

I’m really excited about this project.  Andrew Peel, a colleague at Leeds, has been working on the evolution of beetles (and animals in general) for a while and uses Tribolium as a model system.  I have been interested in the ecology of this system for some time and this project represents us banging our brains together. In particular, there are lots of nice ways that we can incorporate Andrew’s contemporary genomic techniques (e.g. RNAi) to test for genetic drivers of ecological phenomena.  The species is also an important pest species of stored grain, making any advances potentially applicable to pest control.

Note that both of these are “competitively funded”, which means that there are more projects than we can fund.  We interview candidates for all projects and then award the best candidates the projects that they applied for.  There are more details on the website, including how to apply.  Deadline is 24th January 2014.

References:
(1) Hassall C, Thompson DJ (2012) Study design and mark recapture estimates of dispersal: a case study with the endangered damselfly Coenagrion mercuriale. Journal of Insect Conservation, 16, 111-120.
(2) Hassall C, Thompson DJ (2010) Accounting for recorder effort in the detection of range shifts from historical data. Methods in Ecology and Evolution, 1, 343-350.
(3) Hassall C, Thompson DJ, Harvey IF (2008) Latitudinal variation in morphology in two sympatric damselfly species with contrasting range dynamics (Odonata: Coenagrionidae). European Journal of Entomology, 105, 939-944.

Communicating camouflage and mimicry: chocolate, hover flies and Teddy Roosevelt

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In September I gave a Cafe Scientifique talk at the Leeds City Museum on the evolution of mimicry and camouflage.  For those of you who aren’t familiar with the concept, Cafe Scientifique offers an opportunity for scientists to give short (or long, depending on how it is run) talks on their research to a general audience and then take questions in an informal setting.  I have always been a fan of this kind of outreach, and when Clare Brown, the curator of Natural History at Leeds Museum asked if I wanted to give a talk I jumped at the opportunity.  I spent a bit of time pulling resources together for the talk and I thought I would post them here in case anybody else could find a use for them.  I have outlined the talk I gave below:Read More »

“Camouflage on the edge” – a new paper on concealing colouration

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In 2012, the US Government cancelled a $5 billion camouflage project under which it had already supplied uniforms to soldiers in Afghanistan.  The pattern of camouflage, called the “universal camouflage pattern” (UCP) was supposed to allow soldiers to blend in equally well in forests, deserts, and urban environments but had been deployed but never properly tested to ensure that it provided proper protection.  When this testing was finally carried out, it demonstrated that the camouflage performed poorly, and was actually putting soldiers at unnecessary risk.  It got so bad that US Army soldiers were trading their uniforms with locals so that they could wear something with appropriate colouration.  What this goes to show is how poorly we understand the mechanisms underlying camouflage, even while we spend enormous amounts of money attempting to exploit the phenomenon.  A new paper that my colleagues (based at Carleton University) and I published today in the Royal Society journal Biology Letters adds a key piece to the camouflage puzzle by illustrating for the first time the mechanism behind “disruptive colouration“.  The paper can be viewed for free at the journal homepage, as can all Biology Letters articles, until 30th November 2013 – go browse, it’s a fascinating journal with short, varied, interesting papers.

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The perils of predictability

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Order is a standard part of nature, from the mathematical patterns found in natural structures to the predictable variation in sunrise times at different times of year. Indeed, animals and plants rely on regular, logical ordering of events.  For example, in my work on pollinator ecology bees rely on seasonal patterns in flower blooming as a food source. But this regularity is a double-edged sword: just as a bee can exploit regularity in flowering times, so can birds exploit the regularity in bee occurrence. A shared synchrony of life cycles brings costs and benefits. And this is where we bring in the Greek sea-god Proteus (pictured right). Proteus was a god who was able to change his form to avoid having to tell the future, and he has given his name to “protean” phenomena – those phenomena that are changeable or unpredictable. We can see a potential benefit in the plants altering their timing of flowering (of exhibiting protean flowering patterns) – if they remain predictable then the bees on which they rely for pollination are also predictable, which means that they are easy to exploit as food for birds. However, unpredictable flowering times might result in flowers occurring when there are no pollinators, which would be bad for both groups. Synchrony in the seasonality of flowers, insects, and birds is a complex association between populations (or even communities) of animals, and this makes evolutionary change slow.Read More »

Species with a chemical defence (but not a chemical offence) live longer

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Dendrobatid frogs are the classic “aposematic” species: they advertise their toxins with bright colours

I wanted to spend a post talking about a new paper that was published recently (3 May 2013) with some colleagues from Carleton University.  It is easy to see the value of tasting bad: predators try to eat you, feel sick, then leave you alone.  Even better if you have bright colours or a strong smell (called “aposematic signals”) to go along with it – that way predators can learn to avoid your colours without having to taste you a second time.  In fact, they don’t have to taste you at all if other animals of your species also have the bad taste and the bright colours.  In theory, this chemical defence should reduce deaths due to predation which means that the prey live longer.Read More »

While we wait for the open access revolution, self-archive!

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I’ve just had a paper published on open access in ecology and evolution, so I thought I would let you know what it’s all about.  I wrote a few weeks ago about how you can often post more of a scientific paper online without violating copyright than you might think.  I went through a couple of journals in which I had published articles, and tried to work out what I could self-archive.  The answer was usually “quite a lot”!  Then someone in the comments popped up and mentioned the SHERPA-ROMEO website, which allows you to search for the name of the journal in which your paper has been published and then shows you the policy on self-archiving.  Well, being the data-lover that I am I decided to check out the rest of the journals in ecology and evolutionary biology (all 165 that were listed on Thomson Reuters Journal Citation Reports).  The results were pretty interesting…

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My PhD thesis in the ten hundred most used words

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Calopteryx splendens femaleInspired by this xkcd comic, and facilitated by this online tool, people have been summarising all kinds of ideas using the 1,000 most common words.  Naturally PhD students have latched onto this as a source of procrastination and, in a show of solidarity, I decided to join them (this was during my lunch break – honest!).  Here’s my PhD thesis:

My work looks at how animals change as the world gets warmer.  My animal is like a fly but it has four flying bits, eats other animals, and has big eyes.  By looking at where people saw these animals in the past, I figured out how the place and time at which they appear changes with how hot it is.   I found that they appear earlier when it is hot, which is interesting because these animals spend most of their lives in water.  Animals in water had not been shown to change when they appear in this way before.   I also looked at the ways in which we look at changes in where animals appear and showed the best way to look at this problem.  Last, I looked at how the form of these animals changes as they move when it gets hotter.  I found that the animals that had moved a long way had a form that made it easy for them to move (like big flying bits).  In short, the changes shown by the animals that I looked at can be used to build a case for a warming world.