Compositional resilience despite dynamical instability in Atlantic Forest stream fish communities following highway construction

Abstract Highway construction causes environmental stressors in streams such as sedimentation, habitat fragmentation, and altered hydrology, yet their impacts on community dynamics beyond simple diversity metrics remain poorly understood. We assessed the effects of highway construction on multiple dimensions of stream fish community dynamics (stability, species turnover, and synchrony) using a 6-year Before-After design at four stream reaches. Following construction, community stability decreased significantly by 49.8% (P = 0.037), driven by a 103.4% increase in species synchrony ( P = 0.022), whereas species turnover remained unchanged (P = 0.938). These findings reveal that although anthropogenic disturbances were sufficient to alter community dynamics, they were not severe enough to cause local species loss, highlighting a state of compositional resilience despite significant dynamical instability. Our results reveal that highway construction impacted community-level temporal functions despite a stable species composition, emphasizing the importance of dynamical metrics in revealing cryptic degradation in stream ecosystems.