Floodplain forests drive fruit-eating fish diversity at the Amazon Basin-scale.

Area of Science:

• Ecology
• Ichthyology
• Conservation Biology

Background:

• Amazonian rivers largely maintain unregulated flow, supporting unique flooded forests.
• These forests host specialized fauna, including frugivorous fish essential for seed dispersal and fisheries.
• Frugivorous fish depend on floodplain forests for food and habitat, playing a key role in ecosystem health.

Purpose of the Study:

• To investigate the drivers of species richness in Amazonian frugivorous fishes.
• To analyze the relationship between fish diversity and floodplain forest characteristics.

Main Methods:

• Utilized linear mixed effects models across the Amazon Basin (~6,000,000 km²).
• Analyzed data for 29 frugivorous fish species (10,058 occurrences) and 2,506 tree species (309,540 occurrences).
• Included predictors such as floodplain forest extent, tree species richness, water biogeochemistry, flood duration, and elevation.

Main Results:

• Frugivorous fish species richness showed heterogeneous patterns across the basin.
• Species richness was positively correlated with floodplain forest extent, tree species richness, and flood duration.
• The natural hydrological regime is key for fish access to forests and fruit availability.

Conclusions:

• Amazonian floodplain ecosystems' capacity to support frugivorous fish relies on extensive, diverse flooded forests.
• Diverse fish assemblages disperse seeds, maintaining forest diversity, which in turn supports fish diversity.
• Conservation strategies must prioritize hydrologically functional floodplain forests for the long-term survival of frugivorous fish and forest sustainability.