Data from: Allegory of a cave crustacean: systematic and biogeographic reality of Halosbaena (Peracarida: Thermosbaenacea) sought with molecular data at multiple scales

Halosbaena Stock, 1976 are small crustaceans found in a number of distant, isolated subterranean locations in the Northern (Caribbean and Canary Islands) and Southern Hemispheres (Christmas Island and north-western Australia in Cape Range, Barrow Island and Pilbara regions). This distribution is surprising for an animal that produces few eggs, has no free-living larval stage, and succours their young in a dorsal brood pouch. It is usually explained by the passive movement of ancestral populations on tectonic plates as the ancient Tethys Ocean spread. We used molecular data (one mitochondrial and three nuclear genes) to reconstruct phylogenies and time-trees to understand their biogeography at the global scale and at four diminishing scales within the Southern Hemisphere. We found: (1) a basal split between species in the Northern and Southern Hemispheres, but the inferred ages of divergences between species are not old enough to be associated with the spread of the Tethys; (2) a recently discovered species from Christmas Island which is the sister to Australian mainland taxa; (3) the one described species from mainland Australia, H. tulki, probably constitutes at least five separate species that reflect local geography (Cape Range west, Cape Range east, Barrow Island, Pilbara low elevation, Pilbara high elevation); (4) the Pilbara high elevation taxon is likely not old enough to have been stranded high inland during an Eocene marine transgression; and (5) phylogeographic breaks within Cape Range west are congruent with other breaks in sympatric cave species.Halosbaena属（Halosbaena Stock, 1976）为小型甲壳动物，分布于北半球（加勒比海与加那利群岛）及南半球（圣诞岛，以及澳大利亚西北部的开普山脉、巴罗岛与皮尔巴拉地区）多处偏远孤立的地下生境中。该类群的分布格局颇为令人费解：其产卵量稀少，无自由生活的幼虫阶段，且依靠背部育幼囊抚育后代。这一分布模式通常被归因于古特提斯洋扩张时期，祖先种群随板块发生的被动迁移。我们依托分子数据（1个线粒体基因与3个核基因）构建系统发育树与时间树，以从全球尺度及南半球内四级递减尺度解析该类群的生物地理学格局。研究结果如下：(1) 南北半球物种种群间存在基部分化分支，但物种间分化时间的推断结果并不古老到可与特提斯洋扩张事件相匹配；(2) 近期在圣诞岛发现的新种为澳大利亚大陆类群的姊妹群；(3) 澳大利亚大陆已描述的唯一物种——H. tulki，实则至少包含5个独立物种，其分化与当地地理格局高度契合（西开普山脉、东开普山脉、巴罗岛、皮尔巴拉低海拔区域、皮尔巴拉高海拔区域）；(4) 皮尔巴拉高海拔类群的分化时间较晚，不足以支持其在始新世海侵时期被隔离于内陆高地的假说；(5) 西开普山脉内部的系统地理分界与同域分布的其他洞穴物种类群的分界一致。