Chemical ecology in cave-dwelling invertebrates: research trends and knowledge gaps

Chemical cues are fundamental for orientation, communication, foraging, reproduction, and defense in subterranean environments, where permanent darkness increases reliance on non-visual sensory systems. Despite their ecological importance, research on the chemical ecology of cave-dwelling invertebrates has never been systematically synthesized. We conducted a systematic review to identify methodological, taxonomic, ecological, and geographic research trends and knowledge gaps. Following the PRISMA protocol, we systematically searched the Web of Science, Scopus, Google Scholar, and complementary sources, compiling 31 eligible studies published up to January 2026. We classified studies according to research approaches (descriptive, functional, or molecular/neurobiological), taxonomic group, ecological specialization, habitat, geographic region, and research topic. Associations between research approaches and taxonomic and ecological categories were evaluated using chi-square tests and standardized residual analyses. Descriptive studies dominated the literature (82%) and remained predominant over time, whereas functional and molecular/neurobiological approaches were consistently underrepresented. Most studies focused on chemosensory organs and exocrine glands, while behavioral, physiological, and mechanistic aspects of chemoreception were rarely investigated. Research effort was concentrated in Europe and the Americas, with no studies from Africa. Taxonomic coverage was strongly biased toward Coleoptera, whereas most arthropod groups, particularly aquatic taxa, remained poorly represented. Functional studies were significantly less frequent in obligate subterranean species (troglobionts/stygobionts), indicating that ecological specialization and limited accessibility constrain mechanistic investigations. Our review demonstrates that current knowledge of chemical ecology in cave-dwelling invertebrates is shaped by pronounced methodological, taxonomic, and geographic biases, highlighting the need for integrative functional and molecular studies across a broader diversity of subterranean taxa and regions.