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Ant behaviour observation

Apr. 7th, 2010 | 05:27 pm
mood: indescribableindescribable

About this time a year ago, I went to the cellar one morning for a shower. As I blearily switched on the washroom light, there was a snap, a crackle, a blue flicker and then darkness. Woke me right up. Once my eyes adjusted, I saw several crispy fried ants under the light switch, as well as several lively ones swarming over it. The light switch was fused and we had to ask a friendly neighbour to wire in a new one. No-one could remember this happening before in the fifty-seven or so years that my family had lived in this house.

This morning, I went blearily down to the cellar to have a shower. Light on. Snap, crackle, zzt. Crispy fried ants under light switch. Switch still works, though.

Electrocuted ants

How did they do that? Why are they suddenly swarming in the exact same spot for two years running? We've always had ants (Lasius niger) in the house, we've never minded them so we haven't done anything to them, but they never used to do this. Ant pheromone trails certainly don't persist long enough to be taken up again after winter is over, they fade in under an hour. There could be something special about that bit of wall, but again, why now all of a sudden? I'm stumped.
Ant path to doom

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Actual science actually being done here

Mar. 28th, 2010 | 10:52 pm
mood: lethargiclethargic
music: skunk anansie

Ever since I did my research traineeship in 2006, I’ve been disappearing to the Turku archipelago for at least a week, often months, every year. I did my own Master’s thesis work there in 2007, and in other years I’ve been a research assistant in other people’s projects. Now, finally, these projects are starting to bring forth actual published articles by my boss Ayco Tack, which means I can actually start writing about them.

I work on the small island of Wattkast, where every oak tree has been painstakingly mapped with GPS.  There’s almost two thousand of them (here’s a picture). Every year we go through the same hundred or so smaller trees, checking every single leaf for certain insects. Looking at every leaf enables us to say when a species is completely absent from a tree. We also count individuals on a subset of the leaves to estimate densities. There’s about thirty or so species we’re looking for, mostly leaf-mining moths and gall wasps, but some other stuff too, including oak mildew.

The work itself is fun: traipsing around a very pretty island, through forests and across fields and pastures, cursing at crappy GPS units and twenty-year-old aerial photographs as you try to find a specific tree. Spending six hours on a particularly huge individual and then stepping back, gazing at the foliage and knowing you've actually checked every single leaf. Climbing extremely dodgy step ladders while holding test tubes containing live moths and untying the bag on the branch you're trying to make them settle on. Coming accross every possible kind of invertebrate going about its business and taking a few really spectacular ones home as pets. Living in cramped quarters with biology geeks of various nationalities, trying to get along and cope with various problems of water supply and cooking logistics. Wattkast has been a big part of my life and it feels slightly magical to see all that seemingly chaotic activity turn into proper research articles.

When you have a study system of several species of specialist plant-feeding insects and their many parasitoids living in an environment where the host plants are distributed at varying densities and you know where every host plant is, there’s a huge number of research options open to you. The spatial setup of the environment can be expected to have effects on all kinds of aspects of ecology, and several aspects have been studied here. What is usually done is to examine a phenomenon in an experimental setting and then compare with the observed natural situation. Over the years I’ve helped with all kinds of experiments as well as the basic survey. The articles that have come out so far have been about work done in the year I was doing my own project, so it’s not actually stuff I worked on, but I was there, pointing and laughing.

The first article examines the effects of various kinds of competition between leaf miners.  In experimental conditions, competition was found to have an effect on leaf miners, but the observational Wattkast data showed that in nature, leaf miners tend to aggregate together on the same trees. At natural densities, which are smaller than experimental densities, competition didn’t seem to be as important a factor as whatever the factor is that causes leaf miners to aggregate. It’s worth going for the best spots even though you’re more likely to have to compete for them with others, because the likelihood of actually encountering a competitor is still pretty small.

In the second article (preprint), the effects of the spatial setting were compared to the effects of host plant attributes on leaf miner distribution. The conclusions were similar to the first article: spatial effects had an appreciable effect on leaf miner community structure, while the differences between host plants of different genotypes didn’t really seem to matter to the leaf miners.

So, combining these two, leaf miners flock together on the same trees in spite of the slightly increased competition.  The trees that everyone wants to be on are not chosen for their superior quality, but rather their location: indeed they are not chosen as much as happened upon with a greater likelihood simply because they are close to lots of other oaks. Other evidence for the importance of spatial effects has already come out of this study system, which is nice since it very neatly vindicates all the incredibly hard work that went into mapping the trees in the first place.

Tack et al. 2009: Competition as a structuring force in leaf miner communities. – Oikos 118: 809-818
Tack et al. 2010: Spatial location dominates over host plant genotype in structuring an herbivore
community. – Ecology, in press.
Gripenberg, S. & Roslin, T. 2005: Host plants as islands: Resource quality and spatial setting as determinants
of insect distribution. – Ann. Zool. Fennici 42: 335-345

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The key to the key

Feb. 20th, 2010 | 06:14 pm
mood: coldcold
music: lamb

I had an insect identification exam the other day. It followed a course where we were taught to identify the lepidopterans, beetles, hymenopterans, dipterans and hemipterans of Finland. We were taught to the level of families (the abovementioned groups are orders, family is the next rank down).

Each order was taught by an expert in that order, so the teaching was extremely inconsistent. The lepidopterist just showed us hundreds of pictures and told us to look at more pictures by ourselves on the internet. He said it's actually easier to learn all the species of Finland (2575) than to learn to identify which families (we learned 55, but there's some more) they belong to. Assigning species to families is difficult even for experienced lepidopterists.

The beetle guy, however, didn't show us a single picture. What he did was give us an identification key, some sample beetles and microscopes and teach us to use them. He said that when people go into rainforests and find beetle species that are totally new to science, it's still quite easy to place them in the right family, as long as they're using an identification key that is appropriate for the geographic region.

The lepidopterist said that the reason butterflies and moths are so hard to classify is that they're a pretty recent group in evolutionary terms. The radiation of the lepidoptera into different families is still ongoing and the intermediates haven't gone extinct yet, which leaves us with a lot of problematic species. He said. The lepidopterans first diverged from other insects probably a bit over 200 million years ago. Beetles originated around 300 million ears ago. Hm.

So of course after a couple of supervised test runs with the beetle key I got so carried away with how perfectly it worked that I didn't practice beetle identification any further. Instead I sweated over the lepidopterans. Got three and a half out of four on them, too. When it came time to identify my four sample beetles, I realised that even with the best key in the world you still have to look at quite a few coxae to know which ones are "medium" and which ones "large". Got two out of four. Bah.

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Don't be very afraid.

Mar. 14th, 2009 | 04:02 pm
mood: calmcalm
music: bob hund: stenåldern kan börja

The museum beetle (Anthrenus museorum) is a household pest but not to be feared unless you have a very precious insect collection. They do like to munch on those. In Finland they're also quite common in nature. I spotted this one walking on the toilet roll this morning. Some frantic scrabbling for the camera with my pants around my ankles followed. Look mum, no tripod!

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Insane in the basement

Mar. 6th, 2009 | 01:11 pm
mood: satisfiedsatisfied

You know when you buy a nice camera for insect photography in January? And spend months desperately looking for something to photograph that isn't dead and under two feet of snow? And you finally snap and start scouring the basement at 3 AM in the hopes of maybe a diapausing moth or some kind of spider? And instead of an insect, you find a big, fat crustacean that has happened upon a scrummy stain on a table mat in the laundry pile? I love that.

I give you Porcellio scaber, Europe's most common woodlouse.


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How much adorableness can you get into 250 micrometers?

Feb. 12th, 2009 | 05:09 pm
mood: gigglygiggly

This much.

These guys, tardigrades, can withstand pressures that are measured in gigapascals. Nobody knows why, since the greatest pressures found on earth are measured in megapascals. That's in the Mariana Trench, and tardigrades don't live there. They live mostly on mosses and in ponds.

Have a noodle about that one as you celebrate Darwin's birthday. Old Chuck's 200 today!

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Blinkered by assumptions

Feb. 10th, 2009 | 04:58 pm
mood: amusedamused

Brown fat, or brown adipose tissue (BAT), is not supposed to be present in adult humans except in certain medical conditions. I'm taking a course in ecological physiology, and we, too, were taught that it doesn't generally occur. But a clever person in my presentation group found this article, entitled "Unexpected evidence for active brown adipose tissue in adult humans", which completely reverses our thinking as well as being a pretty interesting story about how the scientific community sometimes gets it wrong.

BAT is a specialised heat-producing tissue. In normal cellular respiration, mitochondria use fuels (glucose, amino acids, whatever) to produce high-energy molecules that our cells can use to do whatever it is they do. In the process, some of the energy of the fuels is lost as heat. In BAT, the mitochondria skip the production of chemical energy altogether and just produce heat. BAT was known to be present and important in newborn humans, but it was assumed that it disappears during infancy.

BAT in adults was discovered entirely by accident in a procedure called FDG-PET, which is used to detect tumors. FDG is a substance that tracks and labels glucose uptake and can be detected in a PET scan. The patient is kept off food before the scan, and only the tumors should show up as dark, as well as the brain and heart which are always active, and the bladder and kidneys where the FDG is on its way out. But often, weird symmetrical areas around the neck and shoulders would light up. Furthermore, when doctors started routinely combining CT scans with FDG-PET, it became obvious that this wasn't due to muscle tension. The active areas were fat.

So we come to the interesting bit. It should be pretty obvious to a physiologist that these areas are BAT, but they didn't know about the findings because they don't read nuclear medicine journals. The nuclear medicine scientists didn't really care what it was, they just wanted to get it out of the way so they could see their tumors. In trying to accomplish this, they pretty much proved that it was BAT: its glucose uptake is shut down by propanolol, as you would expect from BAT, and it fails to light up if the patient is kept warm during the scan.

The existence of BAT in adult humans neatly explains a lot of stuff for physiologists, but the reason this will be really interesting to a lot of people is that BAT may be significant is human glucose metabolism. This could have applications in obesity therapy, which is probably second only to cold fusion in terms of kaching-factor. But it can sometimes take a long time for new information to trickle down into undergraduate lectures. To his credit, the teacher is all excited about our upcoming presentation and is planning to raid our slides for next year's lectures.

The thing that made me laugh the most is that all I had to do to have found this article myself is look up BAT on Wikipedia.

Nedergaad, J. et al 2007: Unexpected evidence for active brown adipose tissue in humans. - Am J Physiol Endocrinol Metab 293: E444-E452.

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Seriously old galls

Nov. 28th, 2008 | 08:58 am
mood: stressedstressed
music: Belle & Sebastian

I've done my fair share of going through nasty, old and mouldy leaf samples when working on gall rearings, but this is on another scale altogether.

From Labandeira, C.C., Wilf, P., Johnson, K.R., and Marsh, F. 2007. Guide to Insect (and Other) Damage Types on
Compressed Plant Fossils. Version 3.0. Smithsonian Institution, Washington, D.C. 25 p. © 2007 by Smithsonian Institution.

I recently came across this review (Wilf 2008) of studies on insect damage (galling, mining and every other kind of chewing) on fossil leaves. The idea is that studying insect-plant community dynamics in the fossil record gives us tools for predicting, for instance, the effects of climate change on herbivory. Climate changes have happened in the past, and we can sometimes see the results of those changes in the fossil record. Wilf's review examines three hypotheses, but I'll just pick out one because it's related to what I'm currently trying to read for my next book exam (700 pages, no pretty pictures, oh the pain).

Hypothesis: Insect-feeding diversity and frequency correlate with temperature. The increase in insect herbivory towards the equator is observed almost universally, though gallers are a notable exception (I shan't get into that here, it's complicated). The rise in carbon dioxide levels causes plants to photosynthesize more and produce more biomass, but the biomass is less nutritive. The ratio of carbon to nitrogen in the leaves is higher, because there's more carbon available. The insects are forced to eat more leaves to gain the same amount of weight, and thus we have more herbivory. The other mechanism is simply that higher temperatures improve insect performance. But with the fossil record, we can examine temperature change across time in a fixed location, instead of just across latitudes in present time. And the fossil record shows the same pattern: insect herbivory increased and diversified as temperatures rose. There was also an interesting indication that the presumed rise in CO2 might not have changed the nutritive content of the leaves, but it wasn't remotely solid evidence.

Now, paleontology is for me firmly in the category "this, I know from nothing", so I can't generally judge the quality of that stuff. Usually when I read an article about a new fossil species and look at the illustrations, I pretty much have to take the author's word for it: the amazing creature in question just looks like a splotch to me. But I have to say that the fossil leaves seem to me to be a surprisingly good source of information, provided you keep in mind the usual caveats regarding fossilization bias. Wilf also collaborated on a Smithsonian Institution guide to insect damage types on plant fossils (available here as a free pdf), and looking at the leaf mine pictures particularly, I could just see the leaves as they once where. I've looked at I don't know how many thousands of leaves, for hundreds of hours, and I have a lot of faith in the validity of drawing inferences from these fossils.

Wilf P. 2008: Insect-damaged fossil leaves record food web response to ancient climate change and extinction. - New Phytologist 178: 486-502.

Labandeira, C.C., Wilf, P., Johnson, K.R., and Marsh, F. 2007. Guide to Insect (and Other) Damage Types on Compressed Plant Fossils. Version 3.0. Smithsonian Institution, Washington, D.C. 25 p.

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Finnish publicity

Nov. 18th, 2008 | 04:59 pm
mood: excitedexcited

Esitelmöin graduprojektistani pariin otteeseen lähiaikoina:

21.11. klo 18 @ Tieteiden talo (Suomen hyönteistieteellisen seuran kokous)
27.11. klo 18.15  @ Tieteiden talo, sali 404 (Vanamon kokous)

Lisäksi Suomen Luonto päätti vihdoin julkaista juttumme (jee), se tulee joskus ensi keväänä. Eka julkaisu! Tavallaan.

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Nov. 11th, 2008 | 10:55 pm
mood: sleepysleepy

So what were my disagreements with the content of the Helsingin Sanomat article? Well, while it quite correctly pointed out the problem of how cooperation can evolve when non-cooperators do better than cooperators, it posited punishment as a solution to the problem. Punishment is probably part of the solution, but it's not the whole solution, because punishing others is itself a problematic strategy. This is just moving the problem up a level, not solving it.

Punishing others comes with some kind of a cost, and when people construct models of simple strategic games with defectors, nonpunishing cooperators and punishing cooperators, it tends to take some pretty mighty tweaking to get punishers to come out on top and become the norm in the population. Recently, people have been looking at stuff like group selection and voluntary participation (abstract only) as ways for punishing to flourish. Once punishing behaviour is established in the population, it is very stable indeed, but the problem is how to get it established.

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