Field Museum of Natural History, Zoology - Insects, 1400 S. Lake Shore Drive, Chicago, IL 60605, USA.
Mol Phylogenet Evol. 2010 Dec;57(3):1184-93. doi: 10.1016/j.ympev.2010.08.023. Epub 2010 Sep 8.
Giant pill-millipedes (order Sphaerotheriida) are large-bodied millipedes without poison glands which can roll-up into a complete ball. Their disconnected area of distribution spanning South Africa, Madagascar, India, SE Asia, Australia and New Zealand makes them interesting model organisms for biogeographic studies. The here presented phylogeny is based on a molecular dataset covering all areas of distribution with a special focus on Madagascar, where some species of giant pill-millipedes show island gigantism, reaching the size of a baseball. For our study, two mitochondrial genes (partial 16S rRNA and COI) as well as the complete nuclear 18S rDNA were sequenced. While many recent vertebrate studies hint that the ancestors of the recent Malagasy fauna crossed the >350 km wide Mozambique Channel several times, no such crossing was discovered in the Sphaerotheriida. For the first time in a molecular phylogenetic study of soil arthropods, a Madagascar-India group, the family Arthrosphaeridae, is recovered, hinting to a Gondwanan origin of the Sphaerotheriida. The Malagasy-Indian family Arthrosphaeridae forms a monophyletic, statistically well-supported group in all obtained trees. The giant pill-millipedes from Madagascar are paraphyletic because the Malagasy genus Sphaeromimus is the sister-taxon of the Indian Arthrosphaera. In Sphaeromimus, an ecotone shift occurred only once: the spiny forest species Sphaeromimus musicus forms the sister-clade to the species collected in rainforests and littoral rainforests. The two species of the Malagasy genus Zoosphaerium which express island gigantism form a monophyletic group in some trees, but these trees lack good statistical support. Deeper nodes inside the Sphaerotheriida, like the position of the Australian genera Procyliosoma and Epicyliosoma, the Southeast Asian family Zephroniidae and the South African genus Sphaerotherium could not be resolved. This study is the first genetic study inside the order Sphaerotheriida and provides a proper basis for future molecular biogeographic studies in millipedes and soil organisms from Madagascar.
巨型 pill-millipedes（Sphaerotheriida 目）是一种无毒腺的大型千足虫，它们可以卷成一个完整的球。它们分布范围广泛，跨越南非、马达加斯加、印度、东南亚、澳大利亚和新西兰，这使它们成为生物地理研究的有趣模型生物。本研究基于一个涵盖所有分布区域的分子数据集，特别关注马达加斯加，那里的一些巨型 pill-millipedes 物种表现出岛屿巨型化，体型达到棒球大小。我们的研究中，测序了两个线粒体基因（部分 16S rRNA 和 COI）以及完整的核 18S rDNA。虽然最近的许多脊椎动物研究表明，马达加斯加动物群的祖先多次穿越 350 公里宽的莫桑比克海峡，但在 Sphaerotheriida 目中并未发现这种穿越。这是首次在土壤节肢动物的分子系统发育研究中，恢复了一个马达加斯加-印度群，即 Arthrosphaeridae 科，暗示 Sphaerotheriida 目起源于冈瓦纳大陆。马达加斯加-印度的 Arthrosphaeridae 科在所有获得的树中形成一个单系的、统计上支持良好的群。马达加斯加的 Sphaeromimus 是印度 Arthrosphaera 的姊妹分类群，因此巨型 pill-millipedes 是并系的。在 Sphaeromimus 中，生态过渡仅发生过一次：多刺森林物种 Sphaeromimus musicus 与雨林和沿海雨林中采集的物种形成姊妹分支。表达岛屿巨型化的两个马达加斯加属 Zoosphaerium 物种在一些树中形成一个单系群，但这些树缺乏良好的统计支持。在 Sphaerotheriida 目中更深的节点，如澳大利亚属 Procyliosoma 和 Epicyliosoma、东南亚的 Zephroniidae 科和南非的 Sphaerotherium 属的位置，无法得到解决。本研究是 Sphaerotheriida 目中的第一项遗传研究，为未来马达加斯加千足虫和土壤生物的分子生物地理研究提供了适当的基础。
