A fish frontier? Itatiaia expedition and biodiversity repositories reveal gaps in fish occurrences in Brazil's high-altitude aquatic ecosystems

Abstract

Brazil harbors one of the greatest diversities of freshwater fish in the world; however, the presence or absence of fish in high-altitude aquatic ecosystems remains largely unknown. This study aims to investigate fish occurrence on the Itatiaia Plateau (Itatiaia National Park) at altitudes ranging from 2,140 to 2,543 meters, marking one of the highest-altitude fish surveys conducted in Brazil. Additionally, it analyzes gaps in fish distribution above 2,000 meters in Brazil by compiling approximately 1 million occurrence records from digital biodiversity repositories (SpeciesLink, Salve, SIBBr). Results from the Itatiaia expedition and biodiversity repositories converge to indicate a lack of fish records in high-altitude aquatic ecosystems (> 2,000 m) in Brazil. Psalidodon scabripinnis (Jenyns 1842) is the species with the highest recorded altitude ([~]1,944 m). Challenging climatic conditions, physical barriers to dispersal, isolation, historical absence, sampling gaps, and repository biases may be associated with this lack of fish occurrences. This study highlights gaps in knowledge of fish distribution and the potential for future research to discover previously unknown species or species adapted to high altitudes in Brazil.