Lab-meeting on November 25: signalling sexual and species identity

On Wednesday (November 25), I was thinking that we should do two things during our weekly lab-meeting:

1. We will start by discussing the Nature-paper by Billeter et al. of how Drosophila males and females signal sex and species identity using pheromones ("CHC:s").

Tom Gosden wrote about this paper in an earlier bloggpost, and it seems quite exciting also to those of us who are not particularly interested in pheromone communication. Signalling sex and species identity is clearly a general problem of interest to many evolutionary biologists, and not only those working with Drosophila. The paper can be downloaded here.

2. We will also give Anna Runemark som input on her "half-time seminar" that will take place next week at the Animal Ecology department meeting. Anna brings her laptop and some idéas of her presentation, and the rest of us provide feedback to help her.

Same time and place as usual: "Darwin"-room at 10.00, Wednesday November 25. Any fika-volunteer?

An exciting week with the phenotype in the centre of focus: Thesis nailing, lab-meeting (18 November) and dissertation

We have an exciting week in front of us, starting with the nailing of Fabrice Eroukhmanoffs PhD-thesis on Monday 16 October at 15.00. This ceremony will take place at "The Oak" in the bottom floor of the Ecology Building, and drinks will of course be served. Hope to see you all there!

On Wednesday (18 November), we will have our regular lab-meeting in "Darwin" at 10.00. Fabrice will show his Powerpoint-presentation to get some last feedback before the thesis defence on Friday 20 November. We will also discuss a recent paper by David Houle in the journal PNAS, where he suggests that time is now mature for the formation of a new scientific field: "Phenomics". After all the other "-omics"-revolutions in biology (genomics, transcriptomics and proteomics), Houle suggests that we should now return to the most interesting unit of evolution, and what made most of us interested in biology in the first place: The Phenotype. In spite of all the many advances in genomics and other reductionistic fields in molecular biology, our knowledge about how phenotypes evolve, and how they should be measured and quantified is still quite limited. Hopefully, this paper will open up our eyes for a bright future in the field of evolutionary ecology, and give some new idéas for research. You can download the paper here. If the links do not work, contact me or Anna Runemark (anna.runemark@zooekol.lu.se) and try to get a PDF from us instead. By, the way, do we have any "fika-volunteer" on Wednesday morning?

The exciting week does not end on Wednesday, luckily. On Thursday, Fabrice's thesis opponent, Professor Andrew Hendry from McGill University (Canada) will give a research seminar at 13.00 in the "Blue Hall" (note the time: it is one hour earlier than the "official" Thursday seminar which starts at 14.00). Hendry has done a lot of research on rapid evolutionary change in natural populations, gene flow, "eco-evolutionary dynamics" and ecological speciation. Thetitle of Andrew's talk on Thursday 19 November is:

"Ecological speciation (or the lack there-of) in sticklebacks, guppies and Darwin's finches"

Finally, this exciting week with the phenotype in focus will have a grand finale on Friday November 20 in the "Blue Hall" at 10.00, when Fabrice will defend his thesis. I hope as many as possible can and will join in to see Fabrice defending himself against Andrew Hendry, who is known to be a very critical and detail-oriented scientist. Most welcome!

New PhD-thesis in the lab: Fabrice Eroukhmanoff

I am pleased to announce that a new PhD-thesis will now be defended in our group: Fabrice Eroukhmanoff's Magnum Opus "The interplay Between Selection and Constraints on adaptive Divergence and Phenotypic Evolution".

This is the third Ph.D.-student that has finished his/her thesis in our lab, the previous two were Jessica Abbott (2006) and Tom Gosden (2008). You can find an abstract and more informaton about the thesis here. Well done Fabrice!

The thesis will be defended on Friday November 20 in the Blue Hall (Ecology Building). The external opponent will be Professor Andrew Hendry from McGill University Canada, and the thesis committé will consist of Professors Anna Qvarnström (Uppsala University), Karin Rengefors (Limnology, Lund University) and Janne S. Kotiaho (University of Jyväskylä, Finland). The thesis defence is open to everyone, and I encourage you to participate in this exciting event.

Rapid adaptive divergence and FST-QST

Time for another study from the Svensson Lab:

In a recent study published (in early view) in Molecular Ecology, we (Erik Svensson, Anders Hargeby and myself) have quantified phenotypic and quantitative genetic divergence between two ecotypes of our favorite study organism, the aquatic isopod (Asellus aquaticus) in two lakes in southern Sweden. We have tried to assess the relative role of selection and genetic drift during rapid and parallel ecotype divergence events. We demonstrate that for seven quantitative traits, the average QST between ecotypes is significantly greater than the mean FST, which is clearly consistent with a role for divergent selection causing phenotypic and genetic differentiation of these ecotypes. However, some QST-values for traits linked to size-related morphology fall within the distribution of neutral FST-values, whereas it is not the case for pigmentation traits. Our study therefore underscores the need for caution when evolutionary inferences are made from FST-QST analysis.

For instance, many FST-QST studies have investigated large number of populations and traits, without prior ecological and historical knowledge of the system. This aspect is important because if, like it is in our case, you investigate a case of parallel evolution, you may use specific pairwise comparisons as "replicates", and others as “controls”. The hierarchical structure of the populations and their history might therefore be of importance.

Second, neutral markers may sometimes not be so neutral, thus it is important to compare the distributions of FST with the distributions of QST, and not their means, if one wants to infer the role of selection in the divergence process. All these issues have been reviewed in a very nice paper by Whitlock also published in Molecular Ecology in 2008 and that we have discussed in a previous lab-meeting.

A last point I would like to insist on is that of course, this kind of approach will never beat the advantages of directly measuring selection in the wild. However, it might also be tricky to determine is selection is driving divergence between two populations even when estimating selection in the wild, since it is often difficult to encompass all its components at once, for example linked to fecundity, mate choice, intrinsic survival, predation, etc. Thus, by using FST-QST comparisons, one will estimate the role of the “net” selection differential between populations and its role during divergence. And this is also an advantage.

Well, I hope it inspired you to read our paper…

Smells like?

As some of you know I have spent the last 9 months working with Steve Chenoweth at The University of Queensland where we use the model species Drosophila serrata. In this species (and other Drosophila) males court females using a blend of cuticular hyrocarbons (CHCs) that are produced in the oenocytes of both sexes (see pic above), located on the inner surface of the animal’s abdominal cuticle. These CHCs are known to explain around ¼ of male mating success in D.serrata, and are the subject of a lot of work produced by both Mark Blow’s and Steve’s Lab.

With this in mind I wanted to draw your attention to a recent paper in Nature on the important role of the CHC’s produced by another species of Drosophila, D.melanogaster, not only intraspecfic mating interactions, but also species identity and interspecfic matings. In the paper by Billeter et al. (sorry, not open access) they explain how they knocked out the production of the oenocytes of adult male and female D.melanogaster and found some interesting results. Firstly flies missing the oenocytes (oe-) became a hyper-sexual stimulas to other wild caught males. Oe- males and females were courted and mated far more than their wild caught counterparts. By applying different pheromone compounds, singularly, to the oe- individuals they found a slowing in male mating attempts (ie the female pheromones actually put the males off). Another interesting find was that female oe- were actually courted and mated with males from another species (D.simulans), and again by applying one pheromone compound restored the species barrier.

So a few CHC’s in D.melanogaster have been shown to control male-male mating interactions, influence male courting rates and act as a species barrier to other Drosophila males. Think about that next time you try a unisex eau de toilette.

Abstract:

Social interactions depend on individuals recognizing each other, and in this context many organisms use chemical signals to indicate species and sex1. Cuticular hydrocarbon signals are used by insects, including Drosophila melanogaster, to distinguish conspecific indi- viduals from others1–3. These chemicals also contribute to intraspe- cific courtship and mating interactions1–3. However, the possibility that sex and species identification are linked by common chemical signalling mechanisms has not been formally tested. Here we pro- vide direct evidence that a single compound is used to communicate female identity among D. melanogaster, and to define a reproductive isolation barrier between D. melanogaster and sibling species. A transgenic manipulation eliminated cuticular hydrocarbons by ablating the oenocytes, specialized cells required for the expression of these chemical signals. The resulting oenocyte-less (oe2) females elicited the normal repertoire of courtship behaviours from males, but were actually preferred over wild-type females by courting males. In addition, wild-type males attempted to copulate with oe2 males. Thus, flies lacking hydrocarbons are a sexual hypersti- mulus. Treatment of virgin females with the aversive male phero- mone cis-vaccenyl acetate (cVA) significantly delayed mating of oe2 females compared to wild-type females. This difference was elimi- nated when oe2 females were treated with a blend of cVA and the female aphrodisiac (7Z,11Z)-heptacosadiene (7,11-HD), showing that female aphrodisiac compounds can attenuate the effects of male aversive pheromones. 7,11-HD also was shown to have a crucial role in heterospecific encounters. Specifically, the species barrier was lost because males of other Drosophila species courted oe2 D. melano- gaster females, and D. simulans males consistently mated with them. Treatment of oe2 females with 7,11-HD restored the species barrier, showing that a single compound can confer species identity. These results identify a common mechanism for sexual and species recog- nition regulated by cuticular hydrocarbons.

No lab-meeting the coming weeks, but some exciting symposia

This week's Wednesday (28 October), we will not have our usual lab-meeting, and we will probably have a break for a couple of weeks for now, due to (among other things) teaching activities and CAnMove-PI meeting on my part. However, in case somebody wants to utilize "Darwin" on Wednesday, the room is booked between 10 and 12. Feel free to use it!

On Monday and Tuesday, Caroline Isaksson and Tobias Uller from EGI at Oxford University, will visit the department and give two talks (organized by Maria von Post and Andreas Nordén). I would strongly recommend you to go to these seminars, which will take place in the "Red Room" (adjacent to the "Blue Hall"). On Monday there will two regular research seminars on the afternoon, while on Tuesday there will be a "mini-symposium" about applied and societal aspects of ecological research, where I will also contribute with a talk. Here is the schedule for both days:

SEMINAR 26TH OF OCTOBER14.00-15.00 Causes and consequences of oxidative stress in wild animalsCaroline Isaksson

15-15.30 Coffee

15.30-16.30 Why is Sex Determination in Reptiles so Variable? Integrating Development, Ecology & EvolutionTobias Uller


APPLIED ECOLOGICAL SCIENCE - WORKSHOP 27TH OF OCTOBER
Titles and presenters:

1. What can evolutionary ecologists contribute to medicine?
Insights and Inspiration from the World Health Summit
Dr. Tobias Uller, EGI, Oxford University

2. From selfish genes to group selection - implications for society
Prof. Erik Svensson, Lund University

3. Urban ecology
Dr. Caroline Isaksson, EGI, Oxford University

4. Attitudes and biodiversity
Dr. Johan Ahnström, Lund University

Coffee will be served during the afternoon.

Moreover, there will also be another exciting symposium next week, on Friday (30 October), namely a "Darwin-symposium" , organized by the Royal Academy of Sciences and the Royal Physiographic Society (main organizer: Professor Eric Warrant). The speakers include professors Dan-Eric Nilsson from Lund, Siv Andersson from Uppsala and legendary sociobiologist and evolutionary biologist Robert Trivers from the US. Do not miss this! The symposium is a full-day symposium, and you will find more information and directions here. All the talks will take place at "Palaestra" at the main university area (close to "AF-borgen").

Bayesian statistics for next Wednesday meeting

Last lab meeting Erik and Maja told us about a course on the program R and Bayesian statistics in Uppsala they have been attending. Inspired by this we decided to have a meeting where we discuss Bayesian statistics on Wednesday. First we will discuss a review by Beaumont and Rannala which I first read to prepare for a conservation genetic data analysis course last autumn and found really useful as an introduction to the topic. The paper is found here http://www.nature.com/nrg/journal/v5/n4/pdf/nrg1318.pdf

After that Erik and Maja will give a short presentation on what they have learnt in Uppsala.