Tag: Insects

Help us understand mimicry!

Katatrepsis2 Comments

Picture1I have written about mimicry before, describing why most mimics are imperfect and how some mimics imitate not only the appearance of other animals but also their sounds and behaviour. Now, I need your help with an ambitious experiment to test theories about the evolution of mimicry. Most people know that there are harmless animals that have yellow and black stripes to look like stinging bees and wasps. But did you know that there are many thousands of such species, all with different degrees of “bee-ness” or “waspiness”? The new experiment is designed to compare 56 harmless hoverflies with 42 wasps and bees to measure how similar they are. That’s 2,352 unique comparisons! This information will allow us to test exciting new ideas about the evolution of mimicry. There’s only one catch…

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With his beard and odd dress sense, Uncle Sam would have made a fine entomologist!

This particular experiment will use the human brain as a processing tool and the power of the crowd to generate data. It’s a bit like “Strictly Come Mimicking” (or “Mimicking with the Stars“, if you’re in the US): you just need to rate how similar you think the two insects appear out of 10. I’d appreciate it greatly if you could take some time to run through the experiment below. Don’t do it thinking that there is an end, though – there are 2,352 combinations, remember, and the images are randomly paired on each screen! You can access the experiment here:

www.mimicryexperiment.net

My goal is to reach 10 ratings of each pair of insects. That means a total of 23,520 ratings. I know this is a long shot, but that’s the aim, people! Please do share it far and wide! I’ll share regular updates on the blog as the ratings come in (however many or few there are!).

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Climate change interferes with our use of animals to judge water quality

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Background: Water quality is measured in a number of different ways: measuring levels of chemicals and pollutants, measuring temperature and other physical parameters, and monitoring the animals and plants that are living in the water. The theory is that the animals and plants living in the water have certain requirements of their habitat (particularly a need for clean water) and so you can use the presence of certain “fussy” animal groups as a proxy for water quality. The problem is that, under climate change, species are moving around as environmental conditions – especially temperature – changes.  This means that changes in the animal and plant communities at a given site might give the appearance of an increase in water quality while actually the arrival of new species is simply the result of climate change.

What we did: I analysed an extensive dataset of British dragonfly and damselfly (known collectively as the “Odonata”) sightings to look for a pattern of geographical movement since 1960.  Dragonflies and damselflies are an important group in biological water quality monitoring, as they are particularly sensitive to pollution.  I found that the patterns of water quality that would be detected using Odonata at a generic site would appear to change over time with the changes in Odonata communities, independent of any changes in water quality.

Importance: Biological communities are used extensively in the monitoring of freshwaters and this research emphasises the need to take distributional shifts that occur as a result of climate change into account when using this method. It is likely that water quality is improving, with better treatment of wastewater and better enforcement of environmental regulation, but accurate monitoring is the key to continuing improvement. Secondly, this paper demonstrates once more the fact that Odonata are responding to climate change.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “The impact of climate-induced distributional changes on the validity of biological water quality metrics”, was published in the journal Environmental Monitoring and Assessment in 2010. You can find this paper online at the publisher, or on Figshare.

Image credit: Tambako the Jaguar, CC BY-ND 2.0, http://bit.ly/1v8EGcK

Dragonflies get old, just like us!

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Background:  Ageing is thought to be one of the most widespread biological phenomenon, though it has often been said that insects do not live long enough to experience it. Experiments with insects in laboratories under ideal conditions have shown that ageing does occur, but there are very few studies that have demonstrated this in the wild.

What we did: We used two extensive datasets of sightings of the azure damselfly, Coenagrion puella, to look for an effect of “demographic senescence”.  What this means is that the chance of an animal dying on any given day increases as it gets older.  Hundreds of animals were marked and followed for their whole lives over two summers.  The damselflies live for, on average, 7 days after marking and that follows a period of around 10-12 days of maturation.  What we showed was that, even over so short a lifespan, there was a detectable signal of age-related mortality.  We also demonstrated that there were a number of other variables, principally weather and parasites, that also influence the chance of a damselfly dying.

Importance: Ours was only the second study that comprehensively demonstrated ageing in a wild insect population.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Empirical evidence of senescence in adult damselflies (Odonata: Zygoptera)”, was published in the Journal of Animal Ecology in 2010. You can find this paper online at the publisher, or on Figshare.

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

Citizen science needs fancy statistics to detect the impacts of climate change

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Background:  Climate change is causing a range of effects in plants and animals. One of the most noticeable is the colonisation of new areas as the environment warms to a point where animals are able to persist where once they could not. However, the sources of data used to detect these kinds of patterns tend not to be systematically collected and so present unique challenges during analysis. In particular, a lot of existing data on sightings of animals that are used to detect trends under climate change originate from enthusiastic amateurs who make a note of which species they see and where.

What we did: I analysed a series of different methods that have been used to control for the effects of recorder effort bias in the detection of range shifts.  This recorder effort bias occurs when there are far more recorders looking for animals in a later period and so the chance of discovering those extreme populations increases. Thus range shifts could simply be an artefact of increased sampling. I demonstrate that the methods that have been used before vary in the detection of range shifts and that some make more sense than others. I follow this up with a case study on range shifts in British Odonata and make recommendations concerning the most appropriate methods.

Importance: Climate change is an important issue and we need cutting-edge analytical tools if we are to properly assess its impacts on the world. I hope that this paper has contributed to this aim.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Accounting for recorder effort in the detection of range shifts from historical data”, was published in the journal Methods in Ecology and Evolution in 2010. You can find this paper for free online at the publisher.

Image credit: Ken Slade, CC BY-NC 2.0, http://bit.ly/1qAae4a

It’s hard to predict how many species a pond might contain…

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Background:  Ponds have been identified as a very important habitat in the landscape.  They enhance regional biodiversity, help control floodwater, reduce pollution in run-off from agricultural and urban land, and provide greenspace and biodiversity in urban environments.  However, because of their small size (typically less than two hectares), they have been neglected by scientists until the last couple of decades.

What we did: This study used a large dataset of 454 ponds that had been surveyed in the north of England to identify all of the invertebrate and plant species that inhabited them. A wide range of physical, chemical and biological variables were also measured and, as the title of the paper suggests, we investigated which of these variables were related to the species richness of different plant and animal taxa. We were able to predict a reasonable amount of the diversity of invertebrates in general, but predictions varied between groups of invertebrates. In general, more shade and a history of drying up reduced the diversity of all groups.

Importance: It has been shown that landowners and managers tend to manage ponds and other natural resources using “received knowledge”. in other words, there is little evidence base for such management.  Our study demonstrated a few important relationships which can be used to inform this kind of management.

This is part of a series of short lay summaries that describe the technical publications I have authored.  This paper, entitled “Environmental correlates of plant and invertebrate species richness in ponds”, was published in the journal Biodiversity and Conservation in 2011. You can find this paper online at the publisher, or on Figshare.

Image credit: That’s one of mine, CC-BY 3.0.

Ponds are dynamic habitats, which makes it tough to conserve biodiversity…

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Background:  When an area is designated as a site for conservation or special scientific interest that is usually because one or more species of interest have been found or the community as a whole is unique or exceptional. However, the implicit assumption in this approach is that if you come back tomorrow then those species or that community will still be present. If the habitat is dynamic, with frequent population-level extinctions and colonisations, then it may be that this assumption does not hold. Pond ecosystems represent one case where the habitats are small and relatively easily affected by external variables and which may, as a result, vary in their conservation value over time.

What we did: Andrew Hull and Jim Hollinshead have been monitoring ponds in Cheshire (northwest England) for almost 20 years. A set of 51 ponds were surveyed in 1995/6 and again in 2005, meaning that we can test whether or not over this 10-year period there was any change in the conservation value of the ponds. Pond surveys recorded all plant and macroinvertebrate (i.e. invertebrates larger than about 1mm, which was the size of the mesh of the net) species in the ponds and we compared (i) the diversity, and (ii) the conservation value of the ponds between the two surveys. Plants showed similar levels of diversity in both surveys, so highly-diverse ponds in the first survey remained that way in the second. However, invertebrate diversity was not correlated between surveys, meaning that species rich ponds in the first survey did not necessarily remain that way. For both groups there was not correlation between conservation value (calculated based on the rarity of the species in the community) in survey 1 compared to survey 2.

Importance: Ponds are highly variable ecosystems and that is one of the reasons that they support such a wide range of species on a landscape scale. However, it seems that this variability may make it difficult to conserve them adequately, since conservation value is changing over time. This finding supports the conservation of pond clusters, rather than individual sites, which are more likely to contain a stable species pool.

This is part of a series of short lay summaries that describe the technical publications I have authored. This paper, entitled “Temporal dynamics of aquatic communities and implications for pond conservation”, was published in the journal Biodiversity and Conservation in 2012. You can find this paper online at the publisher, or on Figshare.

Image credit: Alison Benbow, CC BY 2.0, http://bit.ly/1l35Tdu

Good mimics have the costumes and the acting skills

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There are lots of ways to fool an observer, and I mentioned quite a few in my post on the Cafe Scientifique talk that I gave in September. However, one aspect that I didn’t mention there was “behavioural mimicry” – where an animal acts like another animal in order to fool a potential predator or prey.  This sort of behaviour has been reported plenty of times in the field, but has never been studied in a systematic way. My collaborators over at Carleton (led by Tom Sherratt and Heather Penney, who collected the data as part of her MSc thesis work) and I have just published a paper (press release here) which provides just such an overview, and tests a few key evolutionary hypotheses along the way.Read More »

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.

Dragonfly intestines: nature’s Swiss Army knife

Katatrepsis5 Comments

“We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind.  Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions; thus in the larva of the dragonfly… the alimentary canal respires, digests and excretes.”

– Charles Darwin, Origin of the Species, Chapter 6Read More »