Changes in fish functional diversity in a neotropical floodplain associated with the invasive Cichla spp.: a long-term perspective

This study evaluated the impact of Cichla spp. on the functional diversity of small fishes in floodplain lakes from 2002 to 2019, Brazil. Using multivariate regression, we analyzed how functional richness, evenness, divergence, and dispersion indices respond to fluctuations in Cichla spp. abundance and seasonal water levels. Preliminary cross-correlations helped clarify the temporal influence of Cichla spp. on these indices. Results revealed a significant correlation between water levels and all functional indices. After controlling for water level variations, increases in Cichla spp. abundance significantly and negatively affected functional richness and dispersion. Specifically, higher Cichla spp. abundance correlated with reduced functional richness and dispersion after lags of 9 and 21 months, respectively. Additionally, at a 9-month lag, functional divergence was negatively associated with Cichla spp. abundance, whereas an 18-month lag showed a positive influence of functional richness on Cichla spp. abundance, suggesting a cyclical interaction. The study indicates that high Cichla spp. abundance can destabilize crucial community segments, particularly smaller fish species, through a feedback loop of impact. Future studies should explore the factors influencing Cichla spp. abundance, focusing on environmental dynamics. Understanding the interactions between these elements will help clarifying Cichla spp. population trends. Interventions are necessary to mitigate propagule pressure and manage Cichla spp. populations effectively within these ecosystems.