Lab-meeting about phenotypic evolution, the ongoing synthesis and assortative mating

Posted by Erik Svensson

This coming lab-meeting (Tuesday March 18, 10.30), I wanted to discuss a recent general research overview and perspective by evolutionary biologist Stevan J Arnold. It is about the ongoing synthesis in evolutionary biology, but it takes a longer historical perspective. It is the "American Society of Naturalist's Adress", and it is published in the same journal. Hopefully, you will get some feeling for where evolutionary quantitative genetics is today, where it has evolved from, and where it will go in the future. Hopefully, you will also agree that this is still a very dynamic and exciting research approach that will continue to provide many new insights in the genomic and postgenomic era, as it is a synthetic approach that adresses questions that cannot and will never be answered by molecular approaches alone.

You will find the title, the abstract and a link to the article below. Related to this article, I will also spend a few minutes showing some simulation results of what disruptive selection gradients are useful for, and how they can be used to say something about the future.

Phenotypic Evolution: The Ongoing Synthesis

(American Society of Naturalists Address)

 

Stevan J. Arnold

Abstract

I explore the proposition that evolutionary biology is currently in the midst of its greatest period of synthesis. This period, which I call the Ongoing Synthesis, began in 1963 and continues at the present time. I use analysis of citations, conduct, and content to compare the Ongoing Synthesis to widely recognized periods of synthesis in the nineteenth and twentieth centuries. To compare content, I focus on phenotypic evolution and compare current efforts with George Gaylord Simpson’s struggle to understand evolution in deep geological time. The essence of current effort is captured by the question, What is the best model for phenotypic evolution? Although many investigators are actively engaged in answering this question, I single out two examples of my own collaborative work for emphasis here. These two studies share three important characteristics: diagnosis of evolutionary pattern using massive data sets, validation of model parameter values using compilations of estimates (e.g., heritability, stabilizing selection, distance to an intermediate optimum), and identification of evolutionary process using alternative models of stochastic evolution. Our primary findings (discovery of the blunderbuss pattern and the result that rare bursts of evolution carry lineages out of established adaptive zones) compare favorably with important insights from the Modern Synthesis.

Visit by Peter and Rosemary grant and lab-meeting this week

This will be quite an exciting week at our department. On Thursday and Friday, we are visited by legendary evolutionary biologists Peter and Rosemary Grant (Princeton University), who are famous for their long-term population and ecological studies of Galápagos Finches on Daphne Major. Rosemary will give a seminar on Thursday (October 6) at 13.15 (note! Not usual time at 14.00) in the "Blue Hall", entitled:  "Evolution of Darwin's Finches: the role of genetics, ecology and behaviour".

The next day, on October 7, Peter will introduce a reseach symposium in honour of the Grant couple with the theme "Microevolution in the wild". This symposium starts at 08.30, with Peter's talk which is entitled: "Microevolution in Darwin´s finches". Other contributions to this symposium comes from two members of our research lab: Anna Runemark and Maren Wellenreuther. The full programme can be found here.


Anna would like to have some feedback an input on her presentation, before the symposium, and we will therefore listen to her during our lab-meeting this week, which will take place on Thursday, October 6 at 10.00 in the seminar room "Fagus" (3rd floor, Ecology Building). Anna will bring fika. After her presentation, we will discuss a recent paper in PNAS, about the link between microevolution and macroevolution, by Uyeda, Hansen, Arnold and Pienaar entitled: "The million year wait for macroevolutionary bursts".

This is a very important paper that adresses the issue of (apparent) evolutionary stasis in phenotypic traits, and how to reconcile this with the observation that natural (and sexual) selection is generally considered to be strong in natural (contemporary) populations, and the fact that there appears to be abundant additive genetic variance for rapid evolutionary change. Yet, it seems to seldom happen, and this is what we are going to discuss. You will find the title and Abstract below. I would also like to recommend the interesting post by Chicago-professor and population geneticist Jerry Coyne who comments upon their findings at his blog "Why Evolution is True". The title of his post summarizes very well the main finding by Uyeda et al: "Want evolutionary change? Wait a million years".

The million-year wait for macroevolutionary bursts

1. Josef C. Uyeda^a,¹,
2. Thomas F. Hansen^b,
3. Stevan J. Arnold^a, and
4. Jason Pienaar^c

+ Author Affiliations

1. ^aDepartment of Zoology, Oregon State University, Corvallis, OR 97331;
2. ^bDepartment of Biology, Centre for Ecological and Evolutionary Synthesis, University of Oslo, 0316 Oslo, Norway; and
3. ^cDepartment of Genetics, University of Pretoria, Pretoria, South Africa 0002

Abstract

We lack a comprehensive understanding of evolutionary pattern and process because short-term and long-term data have rarely been combined into a single analytical framework. Here we test alternative models of phenotypic evolution using a dataset of unprecedented size and temporal span (over 8,000 data points). The data are body-size measurements taken from historical studies, the fossil record, and among-species comparative data representing mammals, squamates, and birds. By analyzing this large dataset, we identify stochastic models that can explain evolutionary patterns on both short and long timescales and reveal a remarkably consistent pattern in the timing of divergence across taxonomic groups. Even though rapid, short-term evolution often occurs in intervals shorter than 1 Myr, the changes are constrained and do not accumulate over time. Over longer intervals (1–360 Myr), this pattern of bounded evolution yields to a pattern of increasing divergence with time. The best-fitting model to explain this pattern is a model that combines rare but substantial bursts of phenotypic change with bounded fluctuations on shorter timescales. We suggest that these rare bursts reflect permanent changes in adaptive zones, whereas the short-term fluctuations represent local variations in niche optima due to restricted environmental variation within a stable adaptive zone.

 

Lab-meeting about gene expression, sexual dimorphism, sexual selection and condition dependence

This week, I was thinking that we should discuss sexual dimorphism from two different perspectives: a "G-matrix" perspective and a gene expression perspective. The two different papers I have chosen hopefully shed different light on sexual selection and the process of sexual selection. The two papers show how sexual selection might leave a signature, either on the molecular level (the first paper) or on the trait-level (the second paper).

The first paper I would like to discuss is from Locke Rowe's group at University of Ontario (Canada), and you can download it here. I heard Locke give a talk about this at the European Evolutionary Biology Meeting ("ESEB") in Italy in August last year, and I already then thought that this was a very interesting subject.

In particular since most of us (at least me!) are not particularly interested in these novel molecular tools per se, but rather wish to understand how they can be used to illuminate problems and processes in phenotypic evolution, at the whole-organism level, I was thinking that we could get some idéa of how transcriptomics might be used to achieve this goal. Hopefully, we will have a good discussion about this on this coming lab-meeting.

The second paper is a more tradition quantitative-genetic study of intersexual genetic correlations by Steve Arnold's group, and this other paper can be downloaded here.

We meet at the usual time and place, i. e.:

Where: "Darwin" room, 2nd floor (Ecology Building)
When: Wednesday, May 5, at 10.15.