Department of Zoology, University of Otago, Dunedin, New Zealand.
J Evol Biol. 2013 Mar;26(3):683-90. doi: 10.1111/jeb.12068. Epub 2013 Jan 3.
There exists remarkable interspecific variation in mitochondrial sequence evolution rates and in mitochondrial genome sizes. A number of hypotheses based on the forces of mutation and selection have been proposed to explain this variation. Among such hypotheses, we test three: 1) the 'longevity-dependent selection', 2) the 'functional constraints' and 3) the 'race for replication' hypotheses, using published mtDNA genomic sequences of 47 Nematoda species. We did not find any relationship between body size (used as a proxy for longevity) and genome size or the substitution rate of protein sequences, providing little evidence for the first hypothesis. Parasitic species from different thermal habitats, as determined by their definitive host type (ectothermal vs. endothermal), did not differ in their rates of protein evolution. Therefore, little support was obtained for the second hypothesis. However, we revealed that mitogenomes of parasites of endotherms were significantly smaller than those of parasites of ectotherms, supporting the race for replication hypothesis. As mitochondrial genomes of endothermal animals are usually more compact than those of ectothermal animals, intriguingly, nematode parasites of endotherms and ectotherms exhibit similar patterns of mtDNA length variation to their hosts.
线粒体序列进化率和线粒体基因组大小在种间存在显著差异。已经提出了许多基于突变和选择力的假说来解释这种变异。在这些假说中，我们使用已发表的 47 种线虫物种的 mtDNA 基因组序列来检验三个假说：1）“长寿相关选择”，2）“功能约束”和 3）“复制竞赛”假说。我们没有发现体长（用作寿命的替代物）与基因组大小或蛋白质序列替代率之间存在任何关系，这为第一个假说提供的证据很少。根据其终宿主类型（外温动物与内温动物）确定的不同热生境的寄生虫在蛋白质进化率方面没有差异。因此，第二个假说得到的支持很少。然而，我们发现内温动物的寄生虫的线粒体基因组明显小于外温动物的寄生虫的线粒体基因组，这支持了复制竞赛假说。由于内温动物的线粒体基因组通常比外温动物的更紧凑，有趣的是，内温动物和外温动物的线虫寄生虫表现出与宿主相似的 mtDNA 长度变化模式。
