School of Biological Sciences, Monash University, Melbourne, VIC, 3800, Australia.
Department of Conservation Ecology and Entomology, Stellenbosch University, Matieland, 7602, South Africa.
Oecologia. 2021 Apr;195(4):873-885. doi: 10.1007/s00442-021-04896-w. Epub 2021 Apr 1.
Trait-environment interactions have contributed to the remarkable plant radiations in the Cape Floristic Region (CFR) of southern Africa. Whether such interactions have also resulted in the diversification of the invertebrate fauna, independently of direct associations with plants is, however, not clear. One candidate where this may be the case is the unusually diverse Collembola genus Seira. Including 89 species in the CFR, many of which are localised habitat specialists, this genus includes many species inhabiting the warm, dry fynbos shrubland-a habitat atypical of usually desiccation-sensitive Collembola. Here, we investigate whether desiccation tolerance may have contributed to the considerable diversity of Seira in the CFR. First, we demonstrate, by measuring vapour pressure deficits (VPD) of the species' microhabitats (fynbos shrubland and moister Afrotemperate Forests), that the fynbos shrublands are dry environments (mean ± S.E. maximum VPD 5.2 ± 0.1 kPa) compared with the Afrotemperate Forest patches (0.3 ± 0.02 kPa) during the summer activity period of Seira. Then we show that Seira species living in these shrublands are more desiccation tolerant (mean ± S.E. survival time at 76% relative humidity: 74.3 ± 3.3 h) than their congeners in the cooler, moister Afrotemperate Forests (34.3 ± 2.8 h), and compared with Collembola species globally (3.7 ± 0.2 h). These results, and a previous demonstration of pronounced thermal tolerance in the fynbos shrubland species, suggest that the diversity of Seira in the CFR is at least partly due to pronounced desiccation and thermal tolerance, which has enabled species in the genus to exploit the hot and dry habitats of the CFR.
性状-环境相互作用促进了非洲南部开普植物区系（CFR）显著的植物辐射。然而，这种相互作用是否导致无脊椎动物区系的多样化，而与植物没有直接关联尚不清楚。一种可能的情况是异常多样化的弹尾目属 Seira。该属在 CFR 中包含 89 个物种，其中许多是局部栖息地的专家，包括许多栖息在温暖、干燥的高山硬叶灌木草原的物种——这是通常对干燥敏感的弹尾目栖息地的典型栖息地。在这里，我们研究了干燥耐受性是否有助于 CFR 中 Seira 的巨大多样性。首先，我们通过测量物种微生境（高山硬叶灌木草原和较湿润的非洲亚热带森林）的蒸气压亏缺（VPD）来证明，与非洲亚热带森林斑块（0.3 ± 0.02 kPa）相比，高山硬叶灌木草原是干燥的环境（夏季 Seira 活动期的平均±S.E.最大 VPD 为 5.2 ± 0.1 kPa）。然后，我们表明生活在这些灌木草原中的 Seira 物种比生活在较凉爽、较湿润的非洲亚热带森林中的同类物种更能耐受干燥（在相对湿度为 76%时的平均±S.E.存活时间：74.3 ± 3.3 小时），与全球的弹尾目物种（3.7 ± 0.2 小时）相比也是如此。这些结果，以及之前在高山硬叶灌木草原物种中明显耐热性的证明，表明 CFR 中 Seira 的多样性至少部分是由于明显的干燥和耐热性，这使该属中的物种能够利用 CFR 的炎热和干燥栖息地。
