Influence of the mutation load on the genomic composition of hybrids between outcrossing and self-fertilizing species.

Hybridization is a natural process whereby two diverging evolutionary lineages reproduce and create offspring of mixed ancestry. Differences in mating systems (e.g.

Why do hybrids turn down sex?

Asexual reproduction is ancestral in prokaryotes; the switch to sexuality in eukaryotes is one of the major transitions in the history of life. The study of the maintenance of sex in eukaryotes has raised considerable interest for decades and is still one of evolutionary biology's most prominent question. The observation that many asexual species are of hybrid origin has led some to propose that asexuality in hybrids results from sexual processes being disturbed because of incompatibilities between the two parental species' genomes.

The Recombination Hotspot Paradox: Co-evolution between PRDM9 and its target sites.

Recombination often concentrates in small regions called recombination hotspots where recombination is much higher than the genome's average. In many vertebrates, including humans, gene PRDM9 specifies which DNA motifs will be the target for breaks that initiate recombination, ultimately determining the location of recombination hotspots. Because the sequence that breaks (allowing recombination) is converted into the sequence that does not break (preventing recombination), the latter sequence is over-transmitted to future generations and recombination hotspots are self-destructive.

Sex Chromosome Degeneration by Regulatory Evolution.

In many species, the Y (or W) sex chromosome is degenerate. Current theory proposes that this degeneration follows the arrest of recombination and results from the accumulation of deleterious mutations due to selective interference-the inefficacy of natural selection on non-recombining genomic regions. This theory requires very few assumptions, but it does not robustly predict fast erosion of the Y (or W) in large populations or the stepwise degeneration of several small non-recombining strata.

Cis-regulator runaway and divergence in asexuals.

With the advent of new sequencing technologies, the evolution of gene expression is becoming a subject of intensive genomic research, with sparking debates upon the role played by these kinds of changes in adaptive evolution and speciation. In this article, we model expression evolution in species differing by their reproductive systems. We consider different rates of sexual versus asexual reproduction and the different type of parthenogenesis (apomixis and the various modes of automixis).

Enhancer Runaway and the Evolution of Diploid Gene Expression.

Evidence is mounting that the evolution of gene expression plays a major role in adaptation and speciation. Understanding the evolution of gene regulatory regions is indeed an essential step in linking genotypes and phenotypes and in understanding the molecular mechanisms underlying evolutionary change. The common view is that expression traits (protein folding, expression timing, tissue localization and concentration) are under natural selection at the individual level.