Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations
Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations
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DOI：
10.1093/gbe/evaa131
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发表时间：
2020-07-01
影响因子：
3.3
通讯作者：
Filatov, Dmitry A.
中科院分区：
文献类型：
--
作者：
Krasovec, Marc;Rickaby, Rosalind E. M.;Filatov, Dmitry A.
遗传多样性预计与种群大小成正比，然而，在大种群中存在一个众所周知的、但无法解释的遗传多样性缺乏--“莱文廷悖论”。更大的种群预计会进化出更低的突变率，这可能有助于解释这一悖论。在这里，我们通过测量一种无处不在的单细胞海洋浮游植物物种huxleyi(Haptophyta)的自发突变率来检验这一猜测，尽管种群规模巨大，但这种物种的遗传多样性不大。湖北乳杆菌突变聚集系的基因组测序显示有455个突变，具有不寻常的GC偏向突变谱。这得到了每个位置的突变率u=5.55x10(-10)(CI 95%：5.05x10(-10)-6.09x10(-10))的估计，这对应于类似于2.7x10(6)的有效种群大小N-e。对于一个无处不在、数量丰富的物种来说，如此适度的N-E令人惊讶，因为这种物种占全球海洋初级生产力的10%。我们的结果表明，即使是非常大的种群也不会进化出低于每个细胞分裂每个核苷酸10(-10)的突变率。因此，浮游生物物种适度的遗传多样性和天文数字的种群规模之间的极端差异，不能用异常低的突变率来解释。
Genetic diversity is expected to be proportional to population size, yet, there is a well-known, but unexplained lack of genetic diversity in large populations-the "Lewontin's paradox." Larger populations are expected to evolve lower mutation rates, which may help to explain this paradox. Here, we test this conjecture by measuring the spontaneous mutation rate in a ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta) that has modest genetic diversity despite an astronomically large population size. Genome sequencing of E. huxleyi mutation accumulation lines revealed 455 mutations, with an unusual GC-biased mutation spectrum. This yielded an estimate of the per site mutation rate mu = 5.55x10(-10) (CI 95%: 5.05x10(-10) - 6.09x10(-10)), which corresponds to an effective population size N-e similar to 2.7x10(6). Such a modest N-e is surprising for a ubiquitous and abundant species that accounts for up to 10% of global primary productivity in the oceans. Our results indicate that even exceptionally large populations do not evolve mutation rates lower than similar to 10(-10) per nucleotide per cell division. Consequently, the extreme disparity between modest genetic diversity and astronomically large population size in the plankton species cannot be explained by an unusually low mutation rate.