Engelstädter Jan, Charlat Sylvain
Department of Biology, UCL Wolfson House, 4 Stephenson Way, London NW1 2HE, UK.
Proc Biol Sci. 2006 Apr 22;273(1589):923-9. doi: 10.1098/rspb.2005.3411.
In addition to their nuclear genome, the vast majority of eukaryotes harbour cytoplasmic genomes, e.g. in mitochondria or chloroplasts. In the majority of cases, these cytoplasmic genomes are transmitted maternally only, leading to selective pressures divergent from those that act on nuclear genes. In particular, cytoplasmic genes, which reduce the fitness of males that carry them, but have no fitness effect in females, are believed to be selectively neutral. Here, we go a step further and argue that in outbreeding populations (i.e. populations with inbreeding avoidance), 'spiteful' cytoplasmic elements that reduce the number of offspring produced by males are in fact selected for. We study this process by means of a stochastic model, analysing both the probability of spread and the impact that such a spiteful cytotype can have on population dynamics. Our results demonstrate that the probability of spread of the spiteful cytotype can be several times higher in outbreeding than in panmictic populations. Spread and fixation of the spiteful cytotype can lead to different qualitative effects on the population dynamics, including extinction, decreased or increased stable population size. We discuss our results in respect to cytoplasmically induced male infertility and cytoplasmic incompatibility.
除了核基因组外，绝大多数真核生物还拥有细胞质基因组，例如存在于线粒体或叶绿体中。在大多数情况下，这些细胞质基因组仅通过母系遗传，这导致了与作用于核基因的选择压力不同的选择压力。特别是，细胞质基因会降低携带它们的雄性的适合度，但对雌性没有适合度影响，据信这些基因在选择上是中性的。在此，我们更进一步指出，在远交种群（即具有避免近亲繁殖的种群）中，实际上会选择那些减少雄性后代数量的“自私”细胞质元件。我们通过一个随机模型来研究这个过程，分析这种自私细胞类型的传播概率及其对种群动态的影响。我们的结果表明，在远交种群中，自私细胞类型的传播概率可能比随机交配种群高出几倍。自私细胞类型的传播和固定会对种群动态产生不同的定性影响，包括灭绝、稳定种群数量减少或增加。我们结合细胞质诱导的雄性不育和细胞质不相容性来讨论我们的结果。
