Sunday, May 29, 2016

How do metaphors shape science? 

Fred Nijhout asked this in the context of genes, development and evolution in 1990. Let us read the (short) paper again and see if the question remains important in 2016.

Nijhout 1990 here

Optional reading: first two pages in Moczek 2012 here

Argumentet 10.00 Tuesday May 31st, fika and coffee

Sunday, May 22, 2016

May 24th: The evolution of sex-specific dominance


 
The evolution of sex-specific dominance is one way that it has been predicted that sexual antagonism can be resolved. The idea is that e.g. male-benefit/female-detriment (autosomal) loci should evolve to be dominant in males but recessive in females. That way benefits are maximized and detriments minimized. However this prediction has previously been based on verbal models only. Here, the authors construct a model to determine whether sex-specific dominance can realistically evolve.
Abstract: Arguments about the evolutionary modification of genetic dominance have a long history in genetics, dating back more than 100 years. Mathematical investigations have shown that modifiers of the level of dominance at the locus of interest can spread at a reasonable rate only if heterozygotes at that locus are common. One hitherto neglected scenario is that of sexually antagonistic selection, which not only is ubiquitous in sexual species but also can generate stable high frequencies of heterozygotes that would appear to facilitate the spread of such modifiers. Here we present a mathematical model that shows that sexually specific dominance modification is a potential outcome of sexually antagonistic selection. Our model predicts that loci with higher levels of sexual conflict should exhibit greater differentiation between males and females in levels of dominance and that the strength of antagonistic selection experienced by one sex should be proportional to the level of dominance modification. We show that evidence from the literature is consistent with these predictions but suggest that empiricists should be alert to the possibility of there being numerous cases of sex-specific dominance. Further, in order to determine the significance of sexual conflict in the evolution of dominance, we need improved measures of sexual conflict and better characterization of loci that modify dominance of genes with sexually antagonistic fitness effects. 

Friday, May 13, 2016

Discussion on asymmetrical introgression of a sexual signal of the red-backed fairywren

For next week's lab meeting (May 17, 2016), I think it might be nice to discuss a paper on asymmetrical introgression of a sexual signal of the red-backed fairywren.

Time & place & "FIKA" as usual!

Title: GENOMIC AND MORPHOLOGICAL ANALYSIS OF A SEMIPERMEABLE AVIAN HYBRID ZONE SUGGESTS ASYMMETRICAL INTROGRESSION OF A SEXUAL SIGNAL

Abstract: Hybrid zones are geographic regions where differentiated taxa meet and potentially exchange genes. Increasingly, genomic analyses have demonstrated that many hybrid zones are semipermeable boundaries across which introgression is highly variable. In some cases, certain alleles penetrate across the hybrid zone in only one direction, recombining into the alternate genome. We investigated this phenomenon using genomic (genotyping-by-sequencing) and morphological (plumage reflectance spectrophotometry) analyses of the hybrid zone between two subspecies of the red-backed fairy-wren (Malurus melanocephalus) that differ conspicuously in a sexual signal, male back plumage color. Geographic cline analyses revealed a highly variable pattern of differential introgression, with many narrow coincident clines combined with several significantly wider clines, suggesting that the hybrid zone is a semipermeable tension zone. The plumage cline was shifted significantly into the genomic background of the orange subspecies, consistent with sexual selection driving asymmetrical introgression of red plumage alleles across the hybrid zone. This interpretation is supported by previous experimental work demonstrating an extra-pair mating advantage for red males, but the role of genetic dominance in driving this pattern remains unclear. This study highlights the potential for sexual selection to erode taxonomic boundaries and promote gene flow, particularly at an intermediate stage of divergence.

Link: http://onlinelibrary.wiley.com/doi/10.1111/evo.12457/full

Friday, May 6, 2016

Lab meeting on thermal adaptation in wall lizard embryos

How do wall lizard embryos adapt to cold climate?


Wall lizards (Podarcis muralis) from Italy and France have recently been introduced to the UK, where embryos have to cope with drastically colder soil temperatures compared to their native range. Incubation experiments have demonstrated that lizards introduced from France and Italy have evolved faster developmental rate at low temperatures compared to their native counterparts. Last field season, we tackled the question of the underlying mechanism by doing a RNA-Seq experiment on native and introduced wall lizard embryos. 

On Tuesday I will take the opportunity and tell you what we found out about the wallies in particular, and about the evolution of gene expression patterns in general.

Also, the lizard room is ready now and whoever is interested can get a little guided tour after the meeting.

And there will be fika, of course.


Friday, April 29, 2016

Lab meeting on female mate choice

Posted by Katrine Lund-Hansen

I thought this week we could read a paper by one of the invited speakers at Evolution in Sweden 2016, Sergey Gavrilets. There are many papers to choose from, so I tried to pick one that should be of general interest, even though it is a quantitative genetic model. So nothing about flies this time :)

Time: May 3rd, 10:00
Where: Argumentet, Ecology Building 2nd floor
Cake: Of course!

Title: The evolution of female mate choice by sexual conflict

Abstract: Although empirical evidence has shown that many male traits have evolved via sexual selection by female mate choice, our understanding of the adaptive value of female mating preferences is still very incomplete. It has recently been suggested that female mate choice may result from females evolving resistance rather than attraction to males, but this has been disputed. Here, we develop a quantitative genetic model showing that sexual conflict over mating indeed results in the joint evolution of costly female mate choice and exaggerated male traits under a wide range of circumstances. In contrast to traditional explanations of costly female mate choice, which rely on indirect genetic benefits, our model shows that mate choice can be generated as a side–effect of females evolving to reduce the direct costs of mating.

Monday, April 25, 2016

Half-time seminar on hermaphrodites and sex chromosome evolution

Posted by Anna Nordén

Hi all,
In addition to the lab meeting tomorrow (April 26th), I will have my half-time seminar in the afternoon entitled:

"Sex Chromosome Evolution & Sexual Antagonism in Hermaphrodites"

Time and place: 14:30, Red Room, Ecology Building.


The opponent will be Dr. Helena Westerdahl, MEMEG.

Everyone is welcome!

Thursday, April 21, 2016

Talk by Viktor Nilsson-Örtman on life-history theory, temperature and metabolic scaling (April 26 2016)



Next week, EXEB postdoc Viktor Nilsson-Örtman will give a talk about his PhD-research at Umeå University and his subsequent  research at Toronto University (Canada), where he has been a VR-funded postdoc in the laboratory of Locke Rowe. Although Viktor primarily studies damselfly larvae, the topic is a very general one that should be of interest to most EXEB members.

When: Tuesday, April 26, 2016
Where: "Argumentet", 2nd floor (Ecology Building)

 Beyond the log-log plot: toward a life history theory of metabolic scaling

Allometric scaling rules are common in biology, but it remains unclear to what extent they reflect fundamental biophysical constraints or natural selection. Two famous examples are the mass-scaling of metabolism (Kleiber’s law) and the temperature-scaling of biological rate traits (the Universal Temperature Dependence). One problem with studies of biological scaling is that they have been performed at the between-species level, even though natural selection can only act within species. By sampling European and North American damselflies over continental scales and performing common garden experiments within a quantitative genetic framework, my work has revealed striking - but previously unrecognized - variation in the size- and temperature-scaling of growth and metabolism at the level where natural selection can act. In addition, through common garden experiments, I have tried to understand the consequences of this variation with respect to ecological interactions, environmental variability and species’ life histories. In this talk, I will try to summarize the main findings from my recent and ongoing work on these topics.