Friday, April 17, 2015

Lab Meeting on Quantitative Genetics

This week in lab meeting we will have a discussion on quantitative genetics. Anna Nordén will present some preliminary results from her PhD work in the hermaphroditic worm, Macrostomum lignano. She is conducting a quantitative genetics study in which she investigated the heritability of fitness through female and male sex roles. Additionally, I suggest that we discuss the following paper that attempts to synthesize quantitative genetic studies with studies of DNA sequence variability in Drosophila.

Hope to see you there! I'll bring fika.

Figure from Bank et al. 2014: Two hypothetical Distributions of fitness effects (DFE) of all possible new mutations.

Causes of natural variation in fitness: Evidence from studies of Drosophila populations

Brian Charlesworth

    DNA sequencing has revealed high levels of variability within most species. Statistical methods based on population genetics theory have been applied to the resulting data and suggest that most mutations affecting functionally important sequences are deleterious but subject to very weak selection. Quantitative genetic studies have provided information on the extent of genetic variation within populations in traits related to fitness and the rate at which variability in these traits arises by mutation. This paper attempts to combine the available information from applications of the two approaches to populations of the fruitfly Drosophila in order to estimate some important parameters of genetic variation, using a simple population genetics model of mutational effects on fitness components. Analyses based on this model suggest the existence of a class of mutations with much larger fitness effects than those inferred from sequence variability and that contribute most of the standing variation in fitness within a population caused by the input of mildly deleterious mutations. However, deleterious mutations explain only part of this standing variation, and other processes such as balancing selection appear to make a large contribution to genetic variation in fitness components in Drosophila.

      Friday, April 10, 2015

      Natural selection on thermal performance in a novel thermal environment

      Next lab meeting paper will be:

      Natural selection on thermal performance in a novel thermal environment

      Michael L. Logana,1, Robert M. Coxb, and Ryan Calsbeeka
      Tropical ectotherms are thought to be especially vulnerable to climate change because they are adapted to relatively stable temperature regimes, such that even small increases in environmental temperature may lead to large decreases in physiological performance. One way in which tropical organisms may mitigate the detrimental effects of warming is through evolutionary change in thermal physiology. The speed and magnitude of this response depend, in part, on the strength of climate-driven selection. However, many ectotherms use behavioral adjustments to maintain preferred body temperatures in the face of environmental variation. These behaviors may shelter individuals from natural selection, preventing evolutionary adaptation to changing conditions. Here, we mimic the effects of climate change by experimentally transplanting a population of Anolis sagrei lizards to a novel thermal environment. Transplanted lizards experienced warmer and more thermally variable conditions, which resulted in strong directional selection on thermal performance traits. These same traits were not under selection in a reference population studied in a less thermally stressful environment. Our results indicate that climate change can exert strong natural selection on tropical ectotherms, despite their ability to thermoregulate behaviorally. To the extent that thermal performance traits are heritable, populations may be capable of rapid adaptation to anthropogenic warming.

      Where: Seminar room "Argumentet", 2nd floor (Ecology Building)
      When: Tuesday, April 14, 10.30
      Fika: An assortment of cookies and fruit. 

      Sunday, April 5, 2015

      Lab-meeting: is there a physical limit to fitness?

      Posted by Erik Svensson

      I hope all ESEB-members have had a Happy Easter. I post somewhat late for the lab-meeting tomorrow, but we will start lightly with a short and fairly recent paper in Science from Rich Lenski's laboratory, which adresses a fundamental question in evolutionary biology: is there a limit to how much fitness can increase? You will find a link to the paper here, and the Abstract is posted below.

      Time and place as usual:

      Where: Seminar room "Argumentet", 2nd floor (Ecology Building)
      When: Tuesday, April 7, 10.30

      Long-Term Dynamics of Adaptation in Asexual Populations

      Friday, March 27, 2015

      Y chromosome diversity

      This Easter Tuesday I thought we could read a paper that would be of interest to the most of us. There are pretty phylogenetic trees for the Svensson lab and the main focus is sex chromosomes, which we like in the Abbott lab :)
      10:30 in Argumentet, I'll bring fika.

      A recent bottleneck of Y chromosome diversity coincides with a global change in culture

      Abstract: It is commonly thought that human genetic diversity in non-African populations was shaped primarily by an out-of-Africa dispersal 50–100 thousand yr ago (kya). Here, we present a study of 456 geographically diverse high-coverage Y chromosome sequences, including 299 newly reported samples. Applying ancient DNA calibration, we date the Y-chromosomal most recent common ancestor (MRCA) in Africa at 254 (95% CI 192–307) kya and detect a cluster of major non-African founder haplogroups in a narrow time interval at 47–52 kya, consistent with a rapid initial colonization model of Eurasia and Oceania after the out-of-Africa bottleneck. In contrast to demographic reconstructions based on mtDNA, we infer a second strong bottleneck in Y-chromosome lineages dating to the last 10 ky. We hypothesize that this bottleneck is caused by cultural changes affecting variance of reproductive success among males.



      Monday, March 23, 2015

      On the utility and wide outreach of the EXEB-blog

      Graph of Blogger page views

      Posted by Erik Svensson

      One thing that became apparent to me at the "Speciation 2015"-meeting last week in California was  how many young colleagues follows this research blog. It is of course very satisfying, as it means that what we publish here has an impact on the scientific community, above and beyond published articles in the classical peer-reviewed article.

      I know from own, first-hand experience that several young colleagues are more active on social media and read blogs, Twitter and Facebook, for instance, compared to more senior colleagues. Whatever one thinks about it this, it is a reality that we need to take in to consideration when we communicate our research and try to recruit new co-workers, such as postdocs and PhD-students.

      Above, you can see the visitor statistics to our blog from May 2010 to March 2015. I started this blog on my own initative, and it was originally called "Erik Svensson Research Laboratory". After Jessica Abbott received a Junior Project Grant from the Swedish Research Council (VR), we decided to change the name to emphasize that it is a group blog, reflecting the collective work of both Jessica, me and more recently Tobias Uller, who joined EXEB last year, as well as our PhD-students and postdocs.

      You can see that we had many readers until we changed the name of the blog to "Experimental Evolution, Ecology & Behaviour" in August 2011, but this probably only reflects the fact that it took time for regular visitors to find the new adress of the blog. The number of blog visitors now seems to be climbing and currently hovers between 2500 and 3000 per month, and we have readers all over the world, albeit a concentration to Europe and the US, which is not unexpected, given the large research communities in these regions.

      Seminar on population genomics of local adaptation by Chris Wheat on March 27


      Posted by Erik Svensson

      This week there will be another EXEB-organized event in the form of a seminar by my visiting colleague Chris Wheat from the Department of Zoology at Stockholm University. Chris research group is focussed on a number of central questions in ecology and evolution, including phenotypic plasticity and local adaptation, and he and his students and postdocs focus mainly on butterflies as their main study organisms. They use genomic and transcriptomic tools to answer questions in evolutionary biology, and the title of Chris talk will be:

      "Local adaptation in animals: a population genomic perspective"

      When: Friday March 27, at 10.30
      Where: TBA, but hopefully "Argumentet" or "Darwin" on 2nd floor (Ecology Building)

      Thursday, March 19, 2015

      Report from "Speciation 2015" and announcement of lab-meeting on landscape genetics

      Posted by Erik Svensson

      I am posting this from Ventura in southern California, where I am currently attending the last day of the "Speciation 2015" Gordon Research Conference (GRC). It has been a very stimulating conference of perfect size (about 100 attendants), and it will hopefully be permanently established as a bi-annual GRC-event after evaluation of the first two conferences (this one, and the next one to be held in 2017). In spite of the fact that speciation has been an extremely hot research topic in evolutionary biology over the last decade or so, I feel that I have learned many new things, met new colleagues in the field and have established some useful contacts and potential collaborations in the future.

      I really hope that in the future, EXEB-members in mine, Jessicas or Tobias groups will participate in these exciting and informal meetings, which will either take place in California or on other GRC-locations (Spain, Italy, Switzerland or China). The location of the next meeting is yet to be determined. You can see the whole programme for the conference here, and I will also briefly tell you a bit about my impressions and thoughts on the lab-meeting next week (see further below). I was responsible for being "Discussion leader" for the "Behavioural Mechanisms"-section, and it went very well, I think.

      For lab-meeting next week, we will have the chance to listen to Rachael Dudaniec, who will summarize her postdoctoral research on landscape genetics and genomics of the common bluetail damselfly (Ischnura elegans). This is work that she has done here in Lund under the supervision of me and Bengt Hansson in MEMEG. Rachael has now obtained a permanent lecturer position in Australia and will move there by the end of March 2015, and this will be the last chance to hear about her research while here.

      Time and locale as usual:

      Where: "Argumentet", 2nd floor, Ecology Building.
      When: Tuesday, March 24 at 10.30