Morgan M T
School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA.
Proc Biol Sci. 2001 Sep 7;268(1478):1817-24. doi: 10.1098/rspb.2001.1741.
Many plants are perennial, but most studies of inbreeding depression and mating system evolution focus on annuals. This paper extends a population genetic model of inbreeding depression due to recessive deleterious mutations to perennials. The model incorporates life history and mating system variation, and multiplicative selection across many genetic loci. In the absence of substantial mitotic mutation, perennials have higher mean fitness and lower, or even negative, inbreeding depression than annuals with the same mating system. As in annuals, self fertilization exposes deleterious recessive mutations to selection, increasing mean fitness and decreasing inbreeding depression. Including mitotic mutation decreases mean fitness while increasing inbreeding depression. Perenniality introduces a kind of selective sieve, such that strongly recessive mutations contribute disproportionately to mean fitness and inbreeding depression. In the presence of high mitotic mutation, this selective sieve may provide a mechanistic basis for high inbreeding depression observed in some long lived perennials. Without substantial mitotic mutation, it is difficult to reconcile genetically based models of inbreeding depression with the empirical generalization that perennials outcross while related annuals self fertilize.
许多植物是多年生的，但大多数关于近亲繁殖衰退和交配系统进化的研究都集中在一年生植物上。本文将一个由于隐性有害突变导致近亲繁殖衰退的群体遗传模型扩展到多年生植物。该模型纳入了生活史和交配系统的变异，以及多个基因位点上的乘法选择。在没有大量有丝分裂突变的情况下，与具有相同交配系统的一年生植物相比，多年生植物具有更高的平均适合度和更低甚至为负的近亲繁殖衰退。与一年生植物一样，自花受精使有害的隐性突变暴露于选择之下，提高了平均适合度并降低了近亲繁殖衰退。包括有丝分裂突变会降低平均适合度，同时增加近亲繁殖衰退。多年生特性引入了一种选择性筛选机制，使得强烈隐性突变对平均适合度和近亲繁殖衰退的贡献不成比例。在存在高有丝分裂突变的情况下，这种选择性筛选机制可能为在一些长寿多年生植物中观察到的高近亲繁殖衰退提供一个机制基础。如果没有大量有丝分裂突变，就很难使基于遗传的近亲繁殖衰退模型与多年生植物异交而相关一年生植物自花受精这一经验性概括相协调。
