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!


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.


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.