Thermal tolerance and heritability in dune-dwelling ants reveal bioindicator potential for climate vulnerability in coastal ecosystems

Climate change is expected to intensify thermal stress in coastal ecosystems, threatening biodiversity and ecosystem functioning. In this study, we investigate species-specific and colony-level variation in thermal tolerance among three psammophilous ant species (Mycetophylax spp.) inhabiting Brazilian coastal dunes. Using critical thermal limits (CTmin and CTmax), linear mixed-effects models, and heritability estimates, we assessed the role of diel activity rhythms and genetic structure in shaping thermal performance. Results revealed that M. simplex, a nocturnal and substrate-specialized species, exhibited significantly lower CTmin and CTmax values compared to diurnal congeners, and that colony identity explained a substantial portion of variance (H² = 0.53 for CTmin, H² = 0.39 for CTmax). These findings suggest limited thermal resilience and evolutionary constraints in M. simplex, reinforcing its potential as a bioindicator of thermal vulnerability. Given projected warming and habitat disturbance in southeastern Brazil, we highlight the importance of integrating functional traits and genetic metrics into environmental monitoring and conservation planning.