Global Diversity Patterns and Threats of Cave Fish

ABSTRACT Aim Cave fish have long fascinated biologists due to their unusual morphology, biology and physiology. Here, we developed the first database of cave fish occurrences, provided the first map of cave fish diversity patterns and evaluated how environmental changes are threatening cave fish diversity across the globe. Location Global. Time Period 21st century. Major Taxa Studies Cave fish, classified as Stygobionts and Stygophiles, are widespread across the phylogeny of freshwater fish, with more than one‐third of fish orders (17/45) and one‐fifth of freshwater fish families (37/185). Methods We collected 1017 records of cave fish through a review of 378 publications and field surveys. We then used species distribution models to project the current and future global distribution of cave fish under varying climatic and geomorphic conditions, while assessing threats posed by multiple environmental stressors. Results We show that a few places in South America and Asia host a striking richness in cave fish species, whereas other regions are almost free from such species. We moreover reveal that almost two‐thirds of the species are not formally named and that knowledge of cave fish diversity is lacunary in several regions from the Global South. Limited dispersal capacities of cave fish are expected to result in substantial habitat loss, as newly suitable or restored habitats remain inaccessible, thereby pushing species at risk of extinction across the globe. Arsenic contamination in groundwater and dam construction were identified as further threats to cave fish in karst and non‐karst regions, respectively. Conclusions We mapped the global patterns of cave fish diversity and richness, assessed exposure risks under changing environmental conditions and revealed substantial knowledge gaps. Our work constitutes a primer for cave fish ecology and paves the way for further studies on the impact of global changes on the fragile but unique subterranean ecosystems.