CNRS, Univ. Lille, UMR 8198 - Evo-Eco-Paleo, F-59000 Lille, France.
Proc Biol Sci. 2021 Sep 8;288(1958):20211127. doi: 10.1098/rspb.2021.1127.
Inbreeding depression, that is the decrease in fitness of inbred relative to outbred individuals, was shown to increase strongly as life expectancy increases in plants. Because plants are thought to not have a separated germline, it was proposed that this pattern could be generated by somatic mutations accumulating during growth, since larger and more long-lived species have more opportunities for mutations to accumulate. A key determinant of the role of somatic mutations is the rate at which they occur, which probably differs between species because mutation rates may evolve differently in species with constrasting life histories. In this paper, I study the evolution of the mutation rates in plants, and consider the population-level consequences of inheritable somatic mutations given this evolution. I show that despite substantially lower somatic and meiotic mutation rates, more long-lived species still tend to accumulate larger amounts of deleterious mutations because of the increased number of opportunities they have to acquire mutations during growth, leading to higher levels of inbreeding depression in these species. However, the magnitude of this increase depends strongly on how mutagenic meiosis is relative to growth, to the point of being close to non-existent in some situations.
近亲繁殖衰退，即近亲繁殖个体相对于远亲繁殖个体的适应度下降，在植物中随着预期寿命的增加而强烈增加。由于人们认为植物没有分离的生殖系，因此有人提出，这种模式可能是由生长过程中积累的体细胞突变引起的，因为较大和寿命较长的物种有更多的机会积累突变。体细胞突变作用的一个关键决定因素是它们发生的速度，由于突变率在具有对比生命史的物种中可能会以不同的方式进化，因此速度可能在物种之间有所不同。在本文中，我研究了植物中突变率的进化，并考虑了在这种进化的情况下，可遗传的体细胞突变对种群水平的影响。我表明，尽管体细胞和减数分裂突变率要低得多，但由于在生长过程中获得突变的机会增加，寿命较长的物种仍然更容易积累大量的有害突变，从而导致这些物种的近亲繁殖衰退程度更高。然而，这种增加的幅度强烈取决于减数分裂相对于生长的诱变程度，在某些情况下，这种增加接近于不存在。
