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Despite their significance in soil ecosystems and their use for investigations of soil ecosystem functioning and in bioindication elsewhere, springtails (Collembola) have not been well investigated in South Africa. Early recognition of their role in soil systems and sporadic systematic work has essentially characterised knowledge of the southern African fauna for some time. The situation is now changing as a consequence of systematic and ecological work on springtails. To date this research has focused mostly on the Cape Floristic Region and has revealed a much more diverse springtail fauna than previously known (136 identifiable species and an estimated 300 species for the Cape Floristic Region in total), including radiations in genera such as the isotomid Cryptopygus. Quantitative ecological work has shown that alpha diversity can be estimated readily and that the group may be useful for demonstrating land use impacts on soil biodiversity. Moreover, this ecological work has revealed that some disturbed sites, such as those dominated by Galenia africana, may be dominated by invasive springtail species. Investigation of the soil fauna involved in decomposition in Renosterveld and Fynbos has also revealed that biological decomposition has likely been underestimated in these vegetation types, and that the role of fire as the presumed predominant source of nutrient return to the soil may have to be re-examined. Ongoing research on the springtails will provide the information necessary for understanding and conserving soils: one of southern Africa's major natural assets.

Specific trait–environment interactions have led to globally unusual botanical radiations in the Cape Floristic Region (CFR) of South Africa. Yet it is unclear whether such interactions have similarly resulted in the diversification of the fauna independently of associations with plants. We explore this question for the Collembola genus Seira, which includes 89 species in the CFR, and appears to have diversified substantially into warm, dry fynbos shrublands—habitats atypical of those usually occupied by Collembola. Specifically, we determine whether thermal tolerance is higher for members of the genus in these shrublands compared with congeners in cooler, moister Afrotemperate Forests in the region, and with Collembola globally. Fynbos‐inhabiting Seira species have remarkable critical thermal maxima (CTmax) of on average 43°C, 5–6°C higher than congeners occupying the Southern Afrotemperate Forests, and Collembola globally, even when taking CTmax variation associated with regional climate into consideration. Thermal tolerance trait variation among the Seira species from different habitats is likely the consequence of variation in habitat temperature: fynbos shrublands are on average ~17°C warmer than Afrotemperate Forests. Moreover, periodic fires in the fynbos have a large effect on microhabitat temperatures, increasing them substantially (by ~7.5°C) in the year after fire, which may be especially relevant in selecting for higher thermal tolerance in species from this habitat. These results suggest that the remarkable richness of Seira in the CFR may in part be due to the evolution of very high CTmax values which have enabled them to take advantage of a hot, dry habitat that is unusual for Collembola. A free Plain Language Summary can be found within the Supporting Information of this article.

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