You are where you live: parasitic nematode mitochondrial genome size is associated with the thermal environment generated by hosts

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 th...线粒体序列进化速率与线粒体基因组大小存在显著的种间差异。目前已有诸多基于突变与选择压力的假说被提出，以解释这种差异。在这类假说中，我们依托已发表的47种线虫动物门（Nematoda）物种的线粒体DNA（mtDNA）基因组序列，对三类假说展开检验：1）「寿命依赖选择假说」，2）「功能约束假说」，3）「复制竞争假说」。我们未发现体型（作为寿命的替代指标）与基因组大小或蛋白质序列替换速率之间存在关联，据此为第一类假说提供的支持证据较为有限。以终宿主类型（变温宿主 vs. 恒温宿主）划分的不同热环境寄生物种，其蛋白质进化速率并无显著差异，因此第二类假说也未获得足够的支持。然而，我们发现寄生于恒温动物的寄生虫的线粒体基因组，显著小于……