Lab-meeting on G-matrix divergence i isopods

This coming Wednesday (16 September), we will discuss genetic correlations and G-matrices in aquatic isopods (Asellus aquaticus). It is a manuscript that Fabrice and I have worked on for quite a while now, and which is one of the papers in his Ph.D.-thesis that he will defend on November 20. Naturally, we would appreciate all constructive input and criticisms so that we can incorporate these before Fabrice will handle in his thesis to the printer on October 20.

This manuscript which deals with morphological variation and quantiative genetics of morphology, should also be of interest to Tina and Sanna, who have been working recently on phenotypic and genetic correlations of behavioural traits in these isopods.

You can get this manuscript by e-mailing me (erik.svensson@zooekol.lu.se) or Fabrice (fabrice.eroukhmanoff@zooekol.lu.se). If Fabrice sends me the last version, I will also send out this manuscript to the group tomorrow (Monday).

Time and place as usual: "Darwin-room" at 10.00 on Wednesday 16 September. Any fika volunteer?

Relaxed selection and loss of non-beneficial traits

In the latest issue of Trends in Ecology & Evolution, there is a review and metaanalysis of the fascinating phenomen of trait loss after the disappearance of selection pressures maintaining the traits. Classical cases is the loss of vision among cave-dwelling fish or loss of flight ability or antipredator adaptations among birds and insects invading oceanic islands with few predators. This study is briefly reviewed at Science Daily, and one of the co-authors is Andrew P. Hendry, the external opponent of Fabrice Eroukhmanoff's Ph.D.-thesis on November 20 2009.

Fascinating questions to adress here is why do some traits disappear fast, while others take much longer time to decay? According to the results it seems as if two factors might be important in determining the speed by which traits are lost when no longer maintained by selection:

1/Traits that are energetically or nutrient-wise costly are more likely to disappear fast. Examples of such traits are the armour-plate reductions in marine sticklebacks, which disappear fast when these sticklebacks invade freshwater environments, where the minerals that are needed to produce these plates are scarce.

2/Traits that have a relatively simple genetic basis, and which are governed by one or a few loci are lost faster than traits governed by many traits. Examples of such traits include the loss of vision among cave-dwelling animals. Although many genes might influence vision, it might be sufficient with mutations in one or a few genes to cause blindness.

These interesting questions also apply to some of the study systems we are working in our lab, e. g. the Podarcis-lizards that Anna studies on the islets in Greece, where predators are few or the isopods that Fabrice have studied in Lake Krankesjön and Lake Tåkern which have invaded a new limnetic habitat (stonewort), where the isopoods seem to have evolved a suite of different anti-predator adaptations, perhaps as a response to a changed predator regime (invertebrates vs. fish) or perhaps even relaxed overall predation.

Is history always written by the victors?

I had planned to write a blogg post on my recent activities with a friend who was visiting us from Sweden. After a wonderful few weeks cavorting around Australia’s east coast including whale watching, snorkelling on the Great Barrier Reef, exploring the rainforests of Daintree (where we found a Hercules moth, see picture) and Springbrook national park (see pic of common tree snake eating what looks like a gecko), camping on the beach at Stradbroke Island and an ill-advised skydive onto a beach north of Brisbane (for pictures of some of these activities see this site) I felt I had enough to write about, even if it broke the recent run of excellent true scientific posts.

But my head was turned by a correspondence letter in this week’s nature about a retrospective book review of Lamarck’s Philosophie Zoologique (Zoological Philosophy) from 1809. Ignoring the small errors pointed out by the correspondence, the book review opened my eyes a little to the misrepresentative way Lamarck is viewed within main stream science (or at least by the english). I have been as guilty as many for lambasting the work of Lamarck (mainly as a way of mocking Fabrice and the French in general), based purely on summaries of his work I have read in undergraduate textbooks. So have we chosen to over look Lamarck’s main contributions to our field? Having only read what is mentioned in the articles above it would be wrong of me to draw any conclusions and opinions from this……but of course I will and I say yes.

So how does science remember those who have gone before? We are dealing with philosophy of history when we look back over the works of those who have preceded us. Even though much of the work is in print, and therefore assumed to be infallible, misreading and misquoting work is something we are all guilty of to some extent. Sometimes it is easier to cite a piece of work based on the general consensus of what was said rather than reading it yourself. So a lesson for us all, if you're fortunate enough for your work to be remembered, just hope that you're lucky enough that it is remembered favourably and that you're not French (just a joke for Fabrice)!

Lab-meeting on intralocus sexual conflict on Wednesday 9 September 2009

This Wednesday (9 September), I thought we should discuss a recent TREE-article about intralocus sexual conflict, its origin and (possible) solution, which you can find here. The authors are Russel Bonduriansky and Steve Chenoweth,the latter Tom Gosden's postdoc host at Queensland University in Australia. It is a timely overview over a rapidly growing field, which was quite evident for those of us who participated in the ESEB-meeting in Turin, where a whole session was dedicated to the fascinating and increasingly popular topic of intralocus sexual conflict.

It was interesting for me to closely have seen this "explosion" of a field, which I have been familiar with for quite a while, but which few (at least in Lund) understood a few years ago, or realized the importance of. I strongly suspect that the term "gender load", which I had difficulties in explaining in some talks I gave in Lund, will soon enter the mainstream language of evolutionary biology. Perhaps future historians of science will see the signs of a minor conceptual and scientific "revolution" here, as people are increasingly viewing the genome not as a peaceful and harmonic and well-functioning "unit", but rather as something is constantly selected in different directions, the end-result becoming a compromise between male and female fitness optima (see figure above).

For those of you want some additional background reading, I can also recommend Robert Cox and Ryan Calsbeek's recent metaanalysis of intralocus sexual conflict, which was published in American Naturalist earlier this year, and which you can find here. You could also download my own paper (co-published with Andrew McAdam and Barry Sinervo) about intralocus sexual conflict over immune defence and how it affects sex-specific signalling in lizards. This paper is in press in Evolution and can be found here.

I suggest that we all read the TREE-review, and those who wants can also study the two other papers as a general background and bring them to the lab-meeting. We meet the usual time: 10.00 on Wednesday morning in "Darwin". Any fika volunteer?

"Human" vs. "animal" evolution

I thought a recent study from PLoS ONE might be of interest to some of you. In this meta-amalysis, McKellar and Hendry have compared within- and among-population phenotypic levels of variation in humans and animals, for body height and body mass. This study is I think very nice because it is clearly conceptualized, and the results are really straight-forward and well discussed. They also used an estimate of variation called CV, the coefficient of variation that was introduced by Houle in 1992 in a paper published in Genetics and that has in my opinion been a bit neglected by quantitative geneticists. This estimate has the advantage of being scale-free, and therefore allows comparisons between populations or species without bias.

They used an impressive dataset of 99 human populations, 210 animal populations and 848 animal species. Their main conclusions are that within-population variation in body height (but not body mass) is relatively low in humans, whereas among-population variation is more or less similar to what one might measure in animal populations. They interpret it as a sign for strong natural selection on body height in human populations which have become locally adapted.

This paper is, I am sure, probably going to be cited in the media, if it has not already been done, and will probably contribute to the growing success of PLoS ONE. Andrew Hendry has also been working on human influence on evolutionary rates of animals and more in particular human influence on beak size bimodality in finches. He is particularly interested in studying cases of rapid evolution and in the way ecology and evolution interacts on contemporary time scales. I am honored to have him as an opponent for my thesis defense that will take place on the 20th of November, and I can already tell you that Andrew will give a talk on these subjects on Thursday the 19th of November, at 13.00 in Blå Hallen at the Ecology Building.

If you are interested in contemporary evolution, if you have no idea what the term "eco-evolutionary dynamics" really means or simply if this PloS ONE paper has intrigued you, I recommend already now that you mark this date in your calendars, because you will probably don’t want to miss this talk.

Thoughts on ESEB and the Morphometrics Workshop

I returned from the ESEB meetings, plus a follow-up workshop on Geometric Morphometrics, last night. Boy am I tired!! I'm on my 3rd cup of coffee this morning and still feel sleepy; more than one good night's sleep may be needed for a full recovery.

I thought the ESEB meeting was outstanding!!! There were lots of great talks, and I got to meet several evolutionary heros of mine, such as Russell Lande and Steve Arnold. Both were present at my talk, and when Lande asked me a question I nearly shat my britches in front of everyone. I don't think anyone noticed. One honest Swede (who will remain anonymous here) told me that my talk "was good, but not as good as your others," an assessment that I can live with. It was my first talk on entirely new material, so I forgive myself; I look forward to a 2nd opportunity! =-) Erik gave a great, wide-ranging talk on fitness trade-offs between fitness related traits. Some of his slides didn't work (the entire meeting suffered from technical misfires), but he was able to recover and present his messages clearly. I particularly appreciated his incorporation of an explicit adaptive landscapes perspective. The talk was also an interesting contrast with Roff's talk (which I also really enjoyed), which was right before Erik's and was a much more traditional quantitative genetic perspective on the same topic (not so wide ranging as Erik's approach).

I am biased I suppose, but I also LOVED LOVED LOVED the talks by Ryan Calsbeek and Robert Cox -- both on intralocus sexual conflict. A year ago I barely knew that this even was; now I want to study it (by the way, Erik, Barry Sinervo, and Andrew McAdam have a super paper in the "Early View" page in Evolution right now on this very topic). Ryan is my next postdoctoral advisor, and Bob is a postdoc in their lab. They both reported on their studies of Anolis lizards. In a nutshell, there is intralocus sexual conflict on body size -- that is, females and males have different optimal body sizes. How is it resolved (or is it?)? In part, it seems that females use cryptic female choice, and sort sperm from large males to make sons, and sperm from small males to make daughters. This maximizes the fitness of offspring. What made the talks great? First, they were intellectually rigorous (I learned a lot). This is the most important part. Second, the slides were perfect. This matters more than some people realize, and is hard to do, too. Every slide was readable (no axes labeled with tiny text), not overproduced, and informative. Third, they are both great speakers, with confident, engaging styles. I'd like to respectfully request that Bob not apply for any jobs that I want. =-)

Finally, Ian Dworkin gave a very cool talk on the last day (I stole a picture from his web page for this blog post). He is basically doing the same project I am (looking at selection on wing shape by predators), but using lab experiments with Drosophila and mantids. He has an amazing study system going here, I think, and can do things Erik and I can't do, such as concordant artificial selection experiments and studies of the genetics of development. I am certain to be citing his papers a lot. I got to speak with Ian, too, and he's a cool dude.

After ESEB I attended a workshop on geometric morphometrics by Chris Klingenberg and Andrea Cardini. It was a great experience for me. Chris and Andrea are both in the "cool dude" category, too. We learned how to use the program MorphoJ, which Chris created. It's an amazing, integrative program that does some analyses no other program does (I have lots of new ideas now!). Both Chris and Andrea are real experts on morphometrics, and it was a great opportunity to have a chance to interact with them and learn from them. That is one of my principles: never pass on the chance to learn from some of the best. We had some great discussion about semilandmarks, which both Chris and Andrea view with skepticism (semilandmarks are placed on edges and outlines and can mathematically slide along along the edge; they do not identify homologous points). 13 of my 16 landmarks are semilandmarks. I believe I convinced them that they work very well for my project, but Chris and Andrea have an excellent point that we must all remember: just because you can mathematically accomplish a task doesn't mean that it has biological relevance. Care is needed. In the case of semilandmarks, they become meaningless when structures twist (for example, during ontogeny) or when one has, for example, pumps 0n the outline with no linking homology. I have no such issues, but these problems are very common. I like my use of semilandmarks because it allows me to look at total shape. Several studies of insect wings have many good landmarks but few (or none) of them are on the wing outline, so that overall wing shape is not quantified, only patterns of homology within the wing. These could in principle change without a change in overall shape.

So, that's that! Two very good meetings, one very full brain.

Adaptation driven by novel mutations or from selection on standing genetic variation?

Our collegue Hopi Hoekstra at Harvard University in the US, who visited us in August last year, has a paper in one of the last issues of Science. You can read a brief report on the website Science Daily here.

At first I was not very excited about this paper, as it appears to be the usual story about the melanocortin receptor (MC1R) and how it affects coat colour patterns in various mice populations, a story that by know is sufficiently wellknown and established so one wonders what remains to be discovered.

MC1R is responsible for dark coat colour in mice that occur in dark habitats (see above), e. g. on the dark lava flows in Arizona, that Hopi Hoekstra has previously studied together with her colleague Michael Nachmann.

However, this new paper has a new twist: it appears as if selection has acted on a novel mutant in deer mice in Nebraska, and this novel that apparently appeared in the population shortly after the last Ice Age, about 8 000 years ago.

Catherine Linnen and Hopi have analyzed genetic variation among these different mice populations and estimated the age of the allele that causes light coat colour in the mice. Light coloured mice carry a certain allele at a gene called Agouti, and this allele is quite young as it shows evidence of a selective sweep through reduction in DNA sequence diversity around that particular allele. Linnen and Hoekstra have thus used the well-known statistical approach of coalescense analysis to infer the age of the novel mutation at the Agouti locus that is causing light coat colour.

This result is important, as it provides some contrast to recent suggestions that novel mutations might not be that important in cases of rapid evolutionary change, which have instead emphasize selection on standing genetic variation in rapid evolutionary change. For instance, rapid evolutionary change need not always to rely on standing genetic variation as suggested by the findings from other systems like sticklebacks. The alternative is instead that rapid adaptive change is driven by a process by which selection in novel environments "picks up" and favours alleles that already segregated in the ancestral population, rather than "waiting" for the emergence of rare novel beneficial mutations (that might take long time to appear).

This process is sometimes also called phenotype sorting, referring to how a polymorphic and variable base populations might become transformed in to a new (monomorphic and less variable) population through the selective increase and selective loss of already existing phenotypes, which are then "filtered" by selection in the novel environment. Something along these lines appears to also be the case in the freshwater isopods that we have studied in our group, and we discussed this earlier this year in a paper published in Journal of Evolutionary Biology, which you can find here.

In summary, the relative importance of selection acting on novel mutations vs. standing genetic variation is probably something that will be discussed a lot the coming years in evolutionary biology and ecology.