Valley-scale hydrogeomorphology drives river fish assemblage variation in Mongolia.

Area of Science:

• Ecology
• Riverine Ecology
• Conservation Biology

Background:

• River hydrogeomorphology is a primary factor influencing aquatic biodiversity and community structure.
• Functional Process Zones (FPZs) offer a framework to quantify hydrogeomorphic heterogeneity in river networks.

Purpose of the Study:

• To investigate the relationship between hydrogeomorphic heterogeneity, quantified by FPZs, and fish assemblage variation.
• To compare this relationship across two distinct Mongolian ecoregions with varying hydrogeomorphic gradients.

Main Methods:

• Delineated FPZs using valley-scale hydrogeomorphic variables at 10 km intervals in forest steppe and grassland river networks.
• Sampled fish assemblages to assess taxonomic and functional beta diversity in relation to FPZs.
• Analyzed occurrence- and abundance-based variations in fish communities.

Main Results:

• Identified 5 FPZs in forest steppe and 6 in grassland river networks.
• Observed higher functional richness in grassland river networks.
• Found significant variation in fish taxonomic composition (species turnover) in grassland and abundance-based variation in both ecoregions.

Conclusions:

• Valley-scale hydrogeomorphology is a significant driver of fish assemblage variation at a macrosystem scale.
• Hydrogeomorphic variables influence both fish community composition and river network carrying capacity.
• Findings can inform macrosystem-scale community ecology research and conservation strategies.