First divergence time estimate of spiders, scorpions, mites and ticks (subphylum: Chelicerata) inferred from mitochondrial phylogeny
First divergence time estimate of spiders, scorpions, mites and ticks (subphylum: Chelicerata) inferred from mitochondrial phylogeny
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DOI：
10.1007/s10493-008-9203-5
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发表时间：
2009-01-01
影响因子：
2.2
通讯作者：
Hoy, Marjorie A.
中科院分区：
文献类型：
--
作者：
Jeyaprakash, Ayyamperumal;Hoy, Marjorie A.
蜘蛛、蝎子、螨虫和扁虱是陆地上最多样化的节肢动物之一，但它们的起源和多样化的时间尚未确定。我们首次使用来自25个分类群的完整线粒体序列估计了这些螯合物的分子分歧时间。对所有线粒体基因进行单独评估或串联后评估。从3个类群中鉴定并删除了3个缺失基因(ND3、6和tRNA-Asp)的序列，以及11个蛋白质编码基因(COI-III、Cytb、ATP8、6、ND1-2、4L和4-5)中进化较快的核糖体RNA(12S和16S)、tRNAs和每个密码子的第三个碱基。来自11个PCG的其余串联序列产生了一个完全分解的系统发育树，并确认所有的螯合类都是单系进化。从每个密码子中去掉第三个碱基对于解决系统发育至关重要，这使得可以使用三个节点来计算深度分歧时间，这些节点与上下先验进行了校准。我们的估计表明，蜘蛛、蝎子、螨类和壁虱的目和类在晚古生代是多样化的，比以前根据化石年代估计所报道的要早得多。扁虱的分化时间估计表明，它们的第一个陆地宿主可能是两栖动物，而不是爬行动物。使用分子数据，我们分离出蜘蛛-蝎子支系，并估计它们在2300万年前的分歧时间为397+/-A。藻类、真菌、植物和动物，包括昆虫，在这些海藻、真菌、植物和动物多样化的时候，在陆地上都有很好的生存。未来的分析，包括来自更多螯合类的线粒体序列，以及核基因(或整个基因组)的纳入，将提供更完整的海龟进化图景，海龟是地球上第二丰富的动物群体。
Spiders, scorpions, mites and ticks (chelicerates) form one of the most diverse groups of arthropods on land, but their origin and times of diversification are not yet established. We estimated, for the first time, the molecular divergence times for these chelicerates using complete mitochondrial sequences from 25 taxa. All mitochondrial genes were evaluated individually or after concatenation. Sequences belonging to three missing genes (ND3, 6, and tRNA-Asp) from three taxa, as well as the faster-evolving ribosomal RNAs (12S and 16S), tRNAs, and the third base of each codon from 11 protein-coding genes (PCGs) (COI-III, CYTB, ATP8, 6, ND1-2, 4L, and 4-5), were identified and removed. The remaining concatenated sequences from 11 PCGs produced a completely resolved phylogenetic tree and confirmed that all chelicerates are monophyletic. Removing the third base from each codon was essential to resolve the phylogeny, which allowed deep divergence times to be calculated using three nodes calibrated with upper and lower priors. Our estimates indicate that the orders and classes of spiders, scorpions, mites, and ticks diversified in the late Paleozoic, much earlier than previously reported from fossil date estimates. The divergence time estimated for ticks suggests that their first land hosts could have been amphibians rather than reptiles. Using molecular data, we separated the spider-scorpion clades and estimated their divergence times at 397 +/- A 23 million years ago. Algae, fungi, plants, and animals, including insects, were well established on land when these chelicerates diversified. Future analyses, involving mitochondrial sequences from additional chelicerate taxa and the inclusion of nuclear genes (or entire genomes) will provide a more complete picture of the evolution of the Chelicerata, the second most abundant group of animals on earth.