Facing a conservation puzzle: ignoring lithology can bias conservation-priority assessments of Brazilian caves

Subterranean ecosystems are increasingly threatened by anthropogenic disturbances and harbor unique biological communities. Nevertheless, current knowledge and conservation assessments of cave biodiversity remain strongly biased toward carbonate systems, leaving substantial gaps regarding caves developed in non-carbonate lithologies. In this context, the present study assessed the conservation priority of 48 non-carbonate caves (14 granitoid and 34 quartzite caves) located in southern Minas Gerais, Brazil, testing whether the incorporation of lithological context improves the accuracy of conservation-priority assessments. The Cave Conservation Priority Index (CCPi) was applied by integrating metrics of biological relevance, including total species richness, relative richness, and troglobitic richness, together with measures of anthropogenic disturbance intensity. When caves were analyzed jointly, without considering lithological differences, 10 of the 14 granitoid caves shifted to lower conservation-priority categories relative to lithology-specific assessments. Among quartzite caves, six exhibited changes in classification, with four shifting to higher and two to lower priority categories. Lithology-specific analyses identified three granitoid caves and two quartzite caves as exhibiting extremely high conservation priority. All remaining granitoid caves were classified as high and medium priority. Quartzite caves exhibited greater heterogeneity, comprising 13 high-priority caves, 16 medium-priority caves, and only three low-priority caves. This pattern is particularly relevant given that ecological and evolutionary dynamics in subterranean environments are strongly influenced by lithology, as rock type can shape key ecological attributes such as species richness, community composition, and the likelihood of harboring cave-restricted taxa. Accordingly, incorporating lithological context into conservation-priority indices is essential to reduce potential biases associated with comparisons among lithologically heterogeneous systems and avoid underestimating the conservation importance of non-carbonate cave systems.