New paper: The Evolutionary Interplay between Adaptation and Self-Fertilization

An Arabidopsis thaliana rosette, one of the most extensively studied self-fertilising plants. Picture from Wikimedia Commons.

I’m excited to announce a new review paper, “The Evolutionary Interplay between Adaptation and Self-Fertilization“, recently published in Trends in Genetics.

One of my long-standing research interests is investigating how self-fertilisation (fertilisation of male and female sex cells that are produced by the same individual) affects the fixation of adaptive mutations in a population. To this end, myself, Sylvain Glémin and Thomas Bataillon have reviewed how self-fertilisation and adaptation interact with each other. After providing an introduction of the basic concepts concerning how self-fertilisation affects beneficial genes, the review focuses on three main points:

1. Self-fertilising species have different adaptation rates. Self-fertilisation can lead to offspring inherting genes from just one parent, as opposed to two under biparental sex. This inheritance mode can create highly uniform genomes, weakening how selection acts on individual mutations, and diminishing the ability for recombination to create new genotypes. (I have previously carried out theoretical investigations on the impact of this reduced effective recombination rate on genetic evolution. For example, self-fertilisation can make it likelier for deleterious mutations to fix with adaptive mutations, or for competing beneficial variants to be lost).
2. Alterations in how adaptation affects genetic diversity. As adaptive mutations fix, so does any neutral variation lying close to it. This creates a distinctive reduction in genetic diversity around adaptive variants, called a ‘selective sweep’. Self-fertilisation can alter these sweep patterns. Furthermore, changes in a species’ population size can skew signals of genetic adaptation; this effect can be more pronounced under this reproductive mode, so the two outcomes have to be disentangled.
3. Polygenic adaptation, where traits are affected by multiple interacting genes, is also affected by self-fertilisation. This mating system can rapidly create genotypes exhibiting extremely high (or low) characteristics, such as height or weight. These extremes may respond more quickly to selection in the short-term, but new genetic combinations may not be as easily created in the long-term.

You can read the (open-access!) paper here. Here’s the abstract:

Genome-wide surveys of nucleotide polymorphisms, obtained from next-generation sequencing, have uncovered numerous examples of adaptation in self-fertilizing organisms, especially regarding changes to climate, geography, and reproductive systems. Yet existing models for inferring attributes of adaptive mutations often assume idealized outcrossing populations, which risks mischaracterizing properties of these variants. Recent theoretical work is emphasizing how various aspects of self-fertilization affects adaptation, yet empirical data on these properties are lacking. We review theoretical and empirical studies demonstrating how self-fertilization alters the process of adaptation, illustrated using examples from current sequencing projects. We propose ideas for how future research can more accurately quantify aspects of adaptation in self-fertilizers, including incorporating the effects of standing variation, demographic history, and polygenic adaptation.