Cave Meiofauna—Models for Ecology and Evolution

Caves can be used as model systems for developing and understanding evolutionary and ecological theory. Yet, most scientists have paid little attention to cave meiofaunal communities, thereby potentially underestimating subterranean biodiversity. To date, meiofauna has been recorded in only 2026 caves, totalling 31% of caves for which information on aquatic fauna is available around the world. However, these records primarily originate from Europe and the Western Mediterranean and focus on target species, rather than on describing entire communities. Of the 1856 meiofaunal species recorded in caves, 699 might be regarded as restricted to subterranean habitats. Most of those species belong to Arthropoda, with Copepoda the richest species group, both in terms of the number of species recorded and the number of taxa restricted to the subterranean world. Different models have been proposed to explain the origin of meiofaunal cave lineages, but testing them is hampered by the lack of phylogenetic information for most taxa. Although the current lack of diversity data renders studies at a community level challenging, studies to date suggest that cave meiofauna might play a central role in carbon cycling and crucially affect the composition of the groundwater in inland and coastal aquifers. The fundamental ecosystem services that aquifers provide and the pivotal role groundwater discharge attains in the chemical balance of the ocean offer new horizons for future research on cave meiofauna. Cave meiofauna might affect our everyday life much more than we have so far imagined.