Posts Tagged Field Trip

Sunday Spinelessness – The end of Drosophila melanogaster? David Winter Apr 25

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It looks like Drosophila melanogaster, the subject of a recent Sunday Spinelessness post, is about to be lost the world. The species itself isn’t under threat of extinction, you can still have them delivered to your door, it’s the name that looks set to go the way of the Brontosaurus.

One of the goals of taxonomy is to give scientists a precise set of terms that refer to a mutually understood group of organisms. The name D. melanogaster is a case in point, geneticists frequently refer to that species as “the fruit fly” but the common name “fruit fly” could equally be applied to the whole genus Drosophila (more than 1400 species), the family Drosophilidae (containing another 50 or so genera) or the related family Tephritidae. Believe it or not, the lack of precision conveyed by the term fruit fly became part of the USA’s 2008 presidential election. Sarah Palin made some snide and ignorant remarks about “fruit fly research” in one of her speeches which were interpreted by scientific types all over the world as a swipe at basic research. People wrote pieces on the importance of D. melanogaster research in understanding human disease and media picked up the story. But Palin wasn’t talking about Drosophila, she was referring to a project on an economically important Tephritid. She was still being ignorant and playing the “aren’t those scientists stupid” card, be she was doing it about a project that stood to help a multi-million dollar industry that employs thousands of people.

Combined phylogenetic tree (“supertree”) stolen from Michael Bok, who redrew it from van der Linde and Houle (2008)

When we say D. melanogaster instead of fruit fly we all know what we’re talking about, and in modern biology a species name can be a key to huge amounts of information. But there’s a problem with Drosophila. The genus as it is currently prescribed is a mess, species currently included in the genus come out in disparate groups in phylogenetic analyses like the one one the left. The solution is obvious, break up the big malformed genus into a set of smaller ones, giving all but one a new name. Such a process is pretty common in taxonomy, and the code used to my animal taxonomists explains how to go about doing it. Each genus has a “type species” which acts as the name bearer and when a genus is split, it’s the group with the type species that keeps the original name. In molecular biology D. melanogaster is very much the name bearing Drosophila (it’s frequently referred to just by that name or even as “the fly”) but the same isn’t true in taxonomy. The type species is D. funebris and no matter how Drosophila is broken up D. funebris and D. melanogaster are going to end up in different genera so melanogaster will lose its forename. But D. melongaster isn’t just any fly – changing that name would render thousands of textbooks, papers and databases out of date.

Kim van der Linde saw the coming of the Drospho-pocalypse, and applied to the International Committee of Zoological Nomenclature (ICZN) to have D. melanogaster installed as the type species, preventing any changes to the taxonomy of the group from changing the species name. A couple of weeks ago the ICZN made their decision: the application was turned down and D. melanogaster will almost certainly have it’s name changed. You can read the decision online – the committee make arguments for their decision with varying degrees of credibility. Perhaps the weakest justification revolves around this mosquito (I couldn’t have two Sunday Spinelessness posts in a row without one photo from me!):

Aedes aegypti  Stegomyia aegypti ?

This photo was taken on Mitiaro in the Cook Islands, and at the time I took I knew for sure that those white striped legs marked it out as Aedes aegypti. If that species of mosquito had bitten me on any other island in the Cooks I wouldn’t have calmly framed a photo, it’s a vector for dengue fever which is, by all accounts, a horrible disease to have (Mitiaro’s population of 200 people isn’t enough to sustain Dengue, and since the main features of the island are two huge brackish lakes fill of mosquito larvae you soon give up on swatting bugs and spraying DEET). But the point of me showing you this photo now is to tell you that mosquito is no longer Aedes aegypti. Some ICZN committee members cited the fact this species has recently been renamed to Stegomyia aegypti as evidence that renaming a widely studied organism isn’t the end of the world, which rather ignores that fact medical workers, ecologists, parasitologists and geneticists have ignored the reassignment entirely and some prominent journals have even issued editorials encouraging researchers to use the “old” name.

Surely in Aedes aegypti we have a model of what will happen when D. melnoagster gets its genus reassignment – taxonomists will refer to it by the new name and the rest of the world will cray on as if nothing had happened. By refusing to make a small change to the existing taxonomy of the group the ICZN runs the risk of driving a gap between the taxonomic community and other scientists. The only good thing to come from the whole ordeal is that “D. melanogaster” will almost certainly become Sophophora melanogaster which tranlates as “dark bodied bearer of knowledge”, a fitting name for such an important fly.

Plenty of other bloggers have been talking about this story, some with quite different takes than mine. You should check out Kim van der Linde who made the the application to the ICZN and has been blogging the aftermarth as well as Micheal at Arthropoda, Chris at Catalogue of Organisms and Dave at Seed.

The tree is from the following paper:

Kim Van der Linde, & David Houle (2008). A supertree analysis and literature review of the genus Drosophila and closely related genera (Diptera, Drosophilidae)Insect Syst. Evol., 39, 241-267

Arachnophilia David Winter Jul 13

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I like spiders. I mean I really like spiders. So, even though my recent field trip to the Cook Islands was all about the landsnails, and I collected hundreds of them, I wasn’t going to miss the opportunity to explore a whole new spider fauna.

It would actually have been impossible to avoid spiders in the cooks, blazing a trail through the bush means you find yourself reflexively expelling air and scrapping an unseen web of you every couple of minutes. The web spinning spiders behind these snares are only the tip of the arachnid iceberg though, so today I’m going share some pictures of a spider that takes a completely different approach to getting fed.

A. whitneei, side on

That’s Athamas whitmeei, a widespread pacific jumping spider. Quite often my search for arboreal snails on the leaves of shrubs on Rarotonga’s mountains would also turn up these guys with their wonderful orange spots (which are worn only by the males). The one in the photo was actually stalking around our motel unit while I was taking photos of snails so I guess they’re quite happy to adapt to different environments.

Look into my eyes…

Unlike their passive, web-spinning cousins jumping spiders need to go out and hunt their food. As a result they have very good vision. The two large, forward-looking eyes can resolve and image onto their retina which appears to be have four different classes of ‘cones’ (one more than our red, green and blue tuned cells) which may allow them to see a much greater range of colours than ourselves.

Even sharp-eyed hunters can fall prey to other hunters. For mammals and birds choosing where to place your eyes is something of a trade off. Forward facing eyes like Athamas’ help you zero in on your target but limit your ability to see around you. Hence sheep with eyes on the side of their head and wolves with forward looking ones. Athamas as no such trade-off to make, having eight eyes in your body plan leaves a couple spare to point backwards!

Look into my eyes…

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