Merry Christmas and Happy New Year from the EXEB-lab in Lund!

Posted by Erik Svensson

On behalf of the EXEB-lab in Lund, I wish all co-workers, including all of our students, postdocs, junior researchers, national and international collaborators a Merry Christmas and a Happy New Year 2014! The year has been succesful, with new grants, excellent publications and two new PhD-students accepted in to the group: John Waller, Katrine Lund-Hansen and Anna Nordén. They have both made a strong start in their research careers and we wish them all good luck for the future.

In 2013, there has also been some notable achievements by former postdocs Yuma Takahashi and Lesley Lancaster, who have both obtained research positions in the UK and Japan, respectively. We wish both Yuma and Natsu good luck as they now will hopefully establish themselves as independent researchers at their new universities.

As for myself, I am very happy with they past year, and on the personal level, what gave me most satisfaction was probably winning the photo competition of the journal "Oikos" (see picture below). My pictures of ovipositing emerald damselflies (Lestes sponsa) will now be on the cover of Oikos in 2014, and apparently also be on the new "app" the journal will soon launch.

I used the prize sum (100 GBP) to buy some books at Amazon, including the autobiography of Richard Dawkins: An appetite for wonder: The making of a scientist. Although I am not as huge and uncritical fan of Richard Dawkins as I used to be, I am looking forward to read this one, as I imagine it will be very interesting and thought-provocative.

Lab-meeting in preparation for "Christmas Meeting"

Posted by Erik Svensson

We meet on Tuesday (December 17) to listen to Anna Nordén, John Waller and perhaps also Qinyang Li to present the final version of their talks on the "Christmas Meeting" of the Evolutionary Ecology Unit (18-19 December). This will be a chance for Anna, John and Qinyang to get some final constructive input on their talks, and for the rest of us to come with constructive suggestions in a friendly atmosphere.

Note that both time  and location of the lab-meeting has been changed, due to teaching commitments on my part. The new time and place is:

Tuesday December 17 at 14.15 in seminar room "Communis" (3rd floor, Ecology Building).

Most welcome!

SOLVING THE PARADOX OF STASIS: SQUASHED STABILIZING SELECTION AND THE LIMITS OF DETECTION

For Tuesday's meeting,

I think we should read about stabilizing selection, since it is the topic I will be presenting on at the Jul unit party. Anyway, links and abstract below as usual. See you at 10.30 and fika will be provided.



SOLVING THE PARADOX OF STASIS: SQUASHED STABILIZING SELECTION AND THE LIMITS OF DETECTION

Benjamin C. Haller and Andrew P. HendryEvolution 2013

Abstract

Despite the potential for rapid evolution, stasis is commonly observed over geological timescales—the so-called “paradox of stasis.” This paradox would be resolved if stabilizing selection were common, but stabilizing selection is infrequently detected in natural populations. We hypothesize a simple solution to this apparent disconnect: stabilizing selection is hard to detect empirically once populations have adapted to a fitness peak. To test this hypothesis, we developed an individual-based model of a population evolving under an invariant stabilizing fitness function. Stabilizing selection on the population was infrequently detected in an “empirical” sampling protocol, because (1) trait variation was low relative to the fitness peak breadth; (2) nonselective deaths masked selection; (3) populations wandered around the fitness peak; and (4) sample sizes were typically too small. Moreover, the addition of negative frequency-dependent selection further hindered detection by flattening or even dimpling the fitness peak, a phenomenon we term “squashed stabilizing selection.” Our model demonstrates that stabilizing selection provides a plausible resolution to the paradox of stasis despite its infrequent detection in nature. The key reason is that selection “erases its traces”: once populations have adapted to a fitness peak, they are no longer expected to exhibit detectable stabilizing selection.

link (to abstract)

link (to paper)

link (to supporting material)

Lab meeting Dec 3: Cognitive differences between the sexes

Posted by Jessica Abbott on behalf of Utku Urhan

Hi All,
The article i have picked for the next lab meeting will be a follow up on intelligence topic from our previous discussion. This new article from "Trends in Cognitive Sciences"  reviews contemporary studies on cognitive sex differences and points out  biological and environmental factors which may affect male and female cognitive abilities and development differently. Authors also discuss possible ways to maximize cognitive potentials of both genders.

The new science of cognitive sex differences
David I. Miller1 and Diane F. Halpern2
1 Department of Psychology, Northwestern University, Evanston, IL 60208, USA
2 Department of Psychology, Claremont McKenna College, Claremont, CA 91711, USA

Abstract
Surprising new findings indicate that many conclusions about sex differences and similarities in cognitive abilities need to be reexamined. Cognitive sex differences are changing, decreasing for some tasks whereas remaining stable or increasing for other tasks. Some sex differences are detected in infancy, but the data are complex and depend on task characteristics. Diverse disciplines have revolutionized our understanding of why these differences exist. For instance, fraternal-twin studies align with earlier literature to help establish the role of prenatal androgens and large international datasets help explain how cultural factors such as economic prosperity and gender equity affect females and males differently. Understanding how biological and environmental factors interact could help maximize cognitive potential and address pressing societal issues.

http://www.cell.com/trends/cognitive-sciences/abstract/S1364-6613%2813%2900232-5

Visit to MAX-lab

This week's lab meeting will be a field trip to MAX-lab, the university's synchotron facility. They've arranged for a tour guide with experience in biology, so we can find out not only what a synchotron does, but also how it can be used in our research field.

We will meet outside the coffee room at 10.15 and walk there together. The tour itself starts at 10.30.

All visitors to MAX-lab need to be registered, so I need to supply a list of participants in advance. If you are planning on coming then please contact me so I can add you to the list.

Sorry that it took so long to get confirmation from MAX-lab.

Lab-meeting on learning, sexual selection and speciation: Invited talk by Tucker Gilman

Posted by Erik Svensson

On Tuesday next week (November 19 2014), we have an invited  speaker and collaborator of mine from University of Manchester: Dr. Tucker Gilman. Tucker is a theoretical evolutionary biologist who has recently become especially interested in the role of learned mate preferences in sexual selection and speciation (hence our collaboration). You can read more about his research and publications here.

Tucker will visit Lund next week for several days, and in case you would like to meet up with him and discuss science, send me an e-mail (erik.svensson@biol.lu.se). We can also perhaps arrange for a pub evening at "Inferno" if somebody is interested in this?

The lab-meeting will begin as usual at 10.30 with some informal chat and "fika" (any fika-volunteer?). Then, at 11.00 Tucker will give his talk, and if you know anybody outside the EXEB-environment who would be interested in attending, please invite them (and I will also send out an announcement). The title of Tuckers talk is:

"Learning to speciate: the role of peak shift in adaptive radiation."

Everybody should be most welcome to this exciting talk and lab-meeting!

P.S. I got the excellent news that Dr. Tom Gosden, a former PhD-student of mine, will return to Lund and the EXEB-lab in January 2014. Looking forward to it! D. S.

What causes the genetic correlation between height and IQ in humans?

Posted by Jessica Abbott

For next week's lab meeting, I've chosen a paper that's a bit heavy on the quant. gen., but which covers an interesting topic: the genetic correlation between height and IQ in humans. It's been previously established that there is a positive genetic correlation between height and IQ (bad news for me, I guess), but the question is what causes this pattern? Is it that the same genes affect both traits? Or is it that assortative mating causes a correlation? This would be possible if for example smart women prefer to mate with tall men. This paper attempts to explore how pleiotropy and assortative mating can contribute to the genetic architecture of sexually selected traits.

The Genetic Correlation between Height and IQ: Shared Genes or Assortative Mating?

Abstract: Traits that are attractive to the opposite sex are often positively correlated when scaled such that scores increase with attractiveness, and this correlation typically has a genetic component. Such traits can be genetically correlated due to genes that affect both traits (“pleiotropy”) and/or because assortative mating causes statistical correlations to develop between selected alleles across the traits (“gametic phase disequilibrium”). In this study, we modeled the covariation between monozygotic and dizygotic twins, their siblings, and their parents (total N = 7,905) to elucidate the nature of the correlation between two potentially sexually selected traits in humans: height and IQ. Unlike previous designs used to investigate the nature of the height–IQ correlation, the present design accounts for the effects of assortative mating and provides much less biased estimates of additive genetic, non-additive genetic, and shared environmental influences. Both traits were highly heritable, although there was greater evidence for non-additive genetic effects in males. After accounting for assortative mating, the correlation between height and IQ was found to be almost entirely genetic in nature. Model fits indicate that both pleiotropy and assortative mating contribute significantly and about equally to this genetic correlation.

Is there room for punctuated equilibrium and species selection in macroevolution?

Posted by Erik Svensson

Next week (Tuesday November 5, 2013 at 10.30) I want to discuss a classical question in macroevolution that was originally suggested by paleontologists Niles Eldredge and Stephen Jay Gould in 1973, but which has gained increased interested with the explosion of molecular phylogenetic information and improved comparative methods: punctuated equilbrium and species selection. A recent TREE-article take a critical look at the evidence, and it should hopefully be an interesting read and stimulate discussion.

The first TREE-article seems critical towards the prospects for punctuated equilibrium, so as a complement (optional reading) I also post a link to an empirical study on extant mammalian body size variation by Folmer Bokma, which is suggestive of punctuated equilbrium. Enjoy that too!

 

Is there room for punctuated equilibrium in macroevolution?

• Matthew W. Pennell ,
• Luke J. Harmon,
• Josef C. Uyeda

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Highlights

•

The theory of punctuated equilibrium is a mix of conceptually distinct parts.

•

We identify and disentangle four questions that are often associated with the theory.

•

We review recent progress towards each of these four questions.

•

Lumping these four questions together as ‘punctuated equilibrium’ is problematic.

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The long-controversial theory of punctuated equilibrium (PE) asserts that speciation causes rapid evolution against a backdrop of stasis. PE is currently undergoing a resurgence driven by new developments in statistical methods. However, we argue that PE is actually a tangle of four unnecessarily conflated questions: (i) is evolution gradualistic or pulsed? (ii) does trait evolution occur mainly at speciation or within a lineage? (iii) are changes at speciation adaptive or neutral? and (iv) how important is species selection in shaping patterns of diversity? We discuss progress towards answering these four questions but argue that combining these conceptually distinct ideas under the single framework of PE is distracting and confusing, and more likely to hinder progress than to spur it.

Extant mammal body masses suggest

punctuated equilibrium

Tiina M. Mattila and Folmer Bokma

Is gradual microevolutionary change within species simultaneously the source of 

macroevolutionary differentiation between species? Since its first publication, Darwin’s original idea that 

phenotypicdifferences between species develop gradually over time, as the accumulation of small selection-induced

changes in successive generations has been challenged by palaeontologists claiming that, instead, new

species quickly acquire their phenotypes to remain virtually unchanged until going extinct again. This

controversy, widely known as the ‘punctuated equilibrium’ debate, remained unresolved, largely owing to

the difficulty of distinguishing biological species from fossil remains. We analysed body masses of 2143

existing mammal species on a phylogeny comprising 4510 (i.e. nearly all) extant species to estimate rates of

gradual (anagenetic) and speciational (cladogenetic) evolution. Our Bayesian estimates from mammals as

well as separate sub-clades such as primates and carnivores suggest that gradual evolution is responsible for

only a small part of body size variation between mammal species.

Lab meeting 29/10: More about inversions

#posted by Maren Wellenreuther

Hi lab members,
let's have a little follow up from last weeks paper and discuss inversions a bit more-they are cool! Kirkpatrik wrote 2010 a neat paper with the title 'How and Why Chromosome Inversions Evolve' and I think that would provide a good basis to get a general idea of their relevance in evolution, and particular in adaptation.

The link to the paper is below:
http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000501

New paper on the influence of epigenetic effects on sex-specific fitness

Male Drosophila melanogaster.
Photo by André Karwath

Posted by Jessica Abbott.

Some colleagues and I published a paper in PLoS One a couple of months ago that I'd like to highlight here. We used male-limited X-chromosome evolution to investigate the influence of epigenetic effects on sex-specific fitness. The main aim of this experiment was actually to look for specialization of the X for male fitness as a result of the experimental evolution, but as a side effect we were able to look for imprinting effects. The experimental males received their sex chromsomes from the "wrong" parent (i.e. they had paternally inherited X's and maternally inherited Y's), which initially decreases male fitness, but which our experimental evolution lines were able to adapt to over time. We had thought that genomic imprinting was a possible explanation for this pattern, but an analysis of gene expression data suggested that the likely cause was rather maternal effects and coevolution between the sex chromosomes.

Epigenetics and Sex-Specific Fitness: An Experimental Test Using Male-Limited Evolution in Drosophila melanogaster. PLoS One 8(7): e70493.
By Jessica K. Abbott, Paolo Innocenti, Adam K. Chippindale, & Edward H. Morrow

Abstract: When males and females have different fitness optima for the same trait but share loci, intralocus sexual conflict is likely to occur. Epigenetic mechanisms such as genomic imprinting (in which expression is altered according to parent-of-origin) and sex-specific maternal effects have been suggested as ways by which this conflict can be resolved. However these ideas have not yet been empirically tested. We designed an experimental evolution protocol in Drosophila melanogaster that enabled us to look for epigenetic effects on the X-chromosome–a hotspot for sexually antagonistic loci. We used special compound-X females to enforce father-to-son transmission of the X-chromosome for many generations, and compared fitness and gene expression levels between Control males, males with a Control X-chromosome that had undergone one generation of father-son transmission, and males with an X-chromosome that had undergone many generations of father-son transmission. Fitness differences were dramatic, with experimentally-evolved males approximately 20% greater than controls, and with males inheriting a non-evolved X from their father about 20% lower than controls. These data are consistent with both strong intralocus sexual conflict and misimprinting of the X-chromosome under paternal inheritance. However, expression differences suggested that reduced fitness under paternal X inheritance was largely due to deleterious maternal effects. Our data confirm the sexually-antagonistic nature of Drosophila’s X-chromosome and suggest that the response to male-limited X-chromosome evolution entails compensatory evolution for maternal effects, and perhaps modification of other epigenetic effects via coevolution of the sex chromosomes.

Effects of sexual selection and viability selection on a chromosomal inversion polymorphism

#posted by Maren Wellenreuther

Dear all,
sorry for the late posting. At next week's EXEB lab meeting we will dive into the world of seaweed flies and discuss a recent paper by Edward and Gilburn on the interaction of sexual selection and viability selection on the maintenance of a large chromosomal inversion polymorphism. Hanna Rosenquist will present the paper.

Evolution. 2013 Jan;67(1):295-302. doi: 10.1111/j.1558-5646.2012.01754.x. Epub 2012 Aug 27.
Male-specific genotype by environment interactions influence viability selection acting on a sexually selected inversion system in the seaweed fly, Coelopa frigida.
Edward DA, Gilburn AS.

Abstract
In the seaweed fly, Coelopa frigida, a large chromosomal inversion system is affected by sexual selection and viability selection. However, our understanding of the interaction between these two selective forces is currently limited as research has focused upon a limited range of environments. We allowed C. frigida larvae to develop in two different algae, Fucus and Laminaria, and then measured viability and body size for each inversion genotype. Significant male-specific genotype-by-environment interactions influenced viability and body size. For males developing in Laminaria, the direction of viability selection acts similarly on the inversion system as the direction of sexual selection. In contrast, for males developing in Fucus, viability selection opposes sexual selection. These results demonstrate that through considering viability selection in different environments, the costs and benefits associated with sexual selection can be found to vary.

New PhD student: Anna Nordén

My name is Anna Nordén and I started as a PhD student in the Section for Evolutionary Ecology in May this year. I am working on intralocus sexual conflict in a hermaphroditic flatworm under the supervision of Dr Jessica Abbott. My project focuses on the role of sexual antagonism in maintaining standing genetic variation in populations. To investigate this, I will measure the response to sex-limited evolution through experiments using a synthetic sex chromosome in the hermaphroditic free-living marine flatworm Macrostomum lignano.

Before, I have worked on assortative mating and sexual selection in Calopteryx damselflies under the supervision of Prof Erik Svensson at Lund University, and on the co-evolutionary relationship between the moth Greya politella and its host plant Lithophragma parviflorum under the supervision of Prof John Thompson at University of California, Santa Cruz.