Evolutionary mysteries in meiosis

Abstract

Meiosis is a key event of sexual life cycles in eukaryotes. Its mechanistic details have been uncovered in several model organisms and most of its essential features have received various and often contradictory evolutionarily interpretations. In this perspective, we present an overview of these often "weird" features. We discuss the origin of meiosis (origin of ploidy reduction and recombination, two-step meiosis), its secondary modifications (in polyploids or asexuals, inverted meiosis), its importance in punctuating life cycles (meiotic arrests, epigenetic resetting, meiotic asymmetry, meiotic fairness) and features associated with recombination (disjunction constraints, heterochiasmy, crossover interference and hotspots). We present the various evolutionary scenarios and selective pressures that have been proposed to account for these features and we highlight that their evolutionary significance often remains largely mysterious. Resolving these mysteries will likely provide decisive steps towards understanding why sex and recombination is found in the majority of eukaryotes.

The evolutionary advantage of fitness‐dependent recombination in diploids: A deterministic mutation–selection balance model

“…On the other hand, it can also breakdown the existing combinations, including even the most successful ones. However, the question of why recombination exhibits certain general features is no less interesting than the initial question of why recombination exists at all (Korol, Preygel, & Preygel, ; Lenormand, Engelstädter, Johnston, Wijnker, & Hang, ). One such feature is recombination's sensitivity to external and/or internal conditions affecting the proportion of recombinants in the progeny.…”

Cis-regulator runaway and divergence in asexuals

“…), but also heterogeneous within genomes, and possibly more frequent in regulatory regions than in genes for many eukaryotes, depending on hotspot location (Lenormand et al. ).…”

“…Apart from the fact that conversion on genes versus regulatory regions may have varying dynamical effects in our model, there is strong empirical evidence indicating that rates of recombination/conversion may markedly differ in these regions (Lenormand et al. ). For simplicity, we assume that when conversion occurs at a locus, the individual becomes homozygous for one of its (randomly chosen) alleles.…”

Parthenogenesis and developmental constraints

“…Contagious parthenogenesis has been proposed for a wide range of taxa and may be a major route to obligate parthenogenesis (Engelstädter, Sandrock, & Vorburger, 2011;Simon et al, 2003). Sporadic parthenogenesis has been hypothesized to represent another route to obligate parthenogenesis, via mutations for better ploidy restoration, more efficient centrosome assembly, and retention of heterozygosity (e.g., Bell, 1982;Lenormand, Engelstädter, Johnston, Wijnker, & Haag, 2016;Seiler, 1961;White, 1973). However, it is uncertain whether the drastic changes of meiosis associated with obligate parthenogenesis can be achieved by gradual evolution.…”