Ecology and conservation of subterranean biodiversity of Greater Lisbon, Portugal

Subterranean ecosystems harbour fauna moulded by extreme and stable conditions such as absence of light, narrow temperature ranges, high humidity and low availability of organic matter. The adaptations of cave fauna, coupled with the isolation of populations, often lead to a higher incidence of endemics and greater vulnerability to environmental changes. These ecosystems face severe threats caused by pollution and overexploitation, habitat loss and climate change, particularly evident in areas of increased human pressure as capitals of countries. In Portugal, more than 100 endemic cave‐adapted species have been identified, and close to its capital, highly urbanized and industrialized, the Greater Lisbon area hosts several unique endemic subterranean species that lack protection measures. We assessed the invertebrate faunal biodiversity and the conservation status of caves in the Greater Lisbon area. Our results show that arthropods dominate, in abundance and richness, the caves of the Greater Lisbon area, followed by molluscs. Ten endemic subterranean species were found, and of the 20 troglobionts recorded, 11 were found in only one cave, 5 in two caves and 4 in three or more. The overall most diverse was Poço Velho Cave, and the most troglobiont‐diverse was Alvide Cave, both in Cascais. Based on our results, we propose a preliminary conservation priority hierarchy for the studied caves. Our findings reveal that Greater Lisbon harbours irreplaceable subterranean habitats, that support diverse and exclusive invertebrate fauna, which face tremendous threats to their survival, underscoring the need for targeted conservation planning and biodiversity monitoring.