Underground evolution: new roots for the old tree of lumbricid earthworms.
Underground evolution: new roots for the old tree of lumbricid earthworms.
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DOI：
10.1016/j.ympev.2014.10.024
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发表时间：
2015-02
影响因子：
4.1
通讯作者：
Pérez-Losada M
中科院分区：
文献类型：
--
作者：
Domínguez J;Aira M;Breinholt JW;Stojanovic M;James SW;Pérez-Losada M
属于蚯蚓科的蚯蚓在陆地温带地区极其丰富。它们影响土壤性质和养分循环，从而塑造植物群落组成和地上食物网。一些蚯蚓也是生态学和毒理学的模式生物。尽管在过去的130年里，人们对蚯蚓进行了大量的研究，但这些生物的进化关系和分类仍然存在很大的争议。由于蚯蚓身体结构的简单性和神秘物种的存在，它们的系统学的解析受到了阻碍。对蚯蚓总科22个外群、84个蚯蚓属(28个属)的160个标本进行了2个核基因、4个线粒体基因和7个线粒体tRNAs序列测定，并对22个形态特征进行了分析。然后，我们应用系统发育学方法的组合，生成了第一个强大的蛔虫科属水平的系统发育图。我们的结果表明，当前的蛔虫科分类和特征进化的基本假设必须修改。我们的年表表明，Lumbricids出现在全北极地区的下白垩世，它们的多样化是由构造作用(如劳拉西亚分裂)和地理隔离驱动的。我们的年表和特征重建分析表明，受精囊数量并不遵循逐渐减少的模式，孤雌生殖在该群中多次出现；同样的分析也表明，上古和厌食蚯蚓都是由内源祖先进化而来的。这些发现强调了形态和生态特征所经历的强烈和多重的变化，挑战了蛔虫科特征停滞的假说。
Earthworms belonging to the family Lumbricidae are extremely abundant in terrestrial temperate regions. They affect soil properties and nutrient cycling, thus shaping plant community composition and aboveground food webs. Some lumbricids are also model organisms in ecology and toxicology. Despite the intense research efforts dedicated to lumbricids over the last 130 years, the evolutionary relationships and taxonomic classification of these organisms are still subject to great debate. Resolution of their systematics is hampered by the structural simplicity of the earthworm body plan and the existence of cryptic species. We sampled 160 earthworm specimens belonging to 84 lumbricid species (28 genera) and 22 Lumbricoidea outgroups, sequenced two nuclear genes, four mitochondrial genes and seven mitochondrial tRNAs and examined 22 morphological characters. We then applied a combination of phylogenetic methods to generate the first robust genus-level phylogeny of the Lumbricidae. Our results show that the current Lumbricidae classification and the underlying hypotheses of character evolution must be revised. Our chronogram suggests that lumbricids emerged in the Lower Cretaceous in the holarctic region and that their diversification has been driven by tectonic processes (e.g. Laurasia split) and geographical isolation. Our chronogram and character reconstruction analysis reveal that spermathecae number does not follow a gradual pattern of reduction and that parthenogenesis arose from sexual relatives multiple times in the group; the same analysis also indicates that both epigeic and anecic earthworms evolved from endogeic ancestors. These findings emphasize the strong and multiple changes to which morphological and ecological characters are subjected, challenging the hypothesis of character stasis in Lumbricidae.