The generality of cryptic dietary niche differences in diverse large-herbivore assemblages

Area of Science:

• Ecology
• Zoology
• Botany

Background:

• Stable species coexistence requires ecological niche differentiation, which is challenging to identify in large mammalian herbivores.
• Existing dietary niche models focus on plant tissue properties, often ignoring plant species identity, with variable empirical support.
• Resource partitioning beyond plant parts may be key to sustaining large-herbivore diversity in African savannas.

Purpose of the Study:

• To conduct a taxonomically explicit analysis of large-herbivore diets using DNA metabarcoding.
• To investigate dietary niche differentiation and its drivers across African savanna ecosystems.
• To understand how dietary partitioning influences community organization and herbivore coexistence.

Main Methods:

• DNA metabarcoding of approximately 4,000 fecal samples from 30 large-herbivore species across 10 sites in seven countries over six years.
• Identification of 893 food plant taxa, with grasses and legumes dominating diets.
• Statistical analysis of diet composition differences between sympatric species.

Main Results:

• Herbivore species consistently partitioned food plant taxa, with 97% of pairwise comparisons showing significant diet dissimilarity.
• Dietary differentiation was pronounced even between strict grazers, strict browsers, and closely related species.
• Niche differentiation was weaker in defaunated areas and stronger in low-rainfall environments, suggesting a role for species interactions and competition.

Conclusions:

• Dietary differentiation among large herbivores is structured along taxonomic lines, complementing partitioning by plant parts and patches.
• This taxonomic partitioning is a significant mechanism driving herbivore coexistence and community assembly in savannas.
• Dietary differences influence community organization, with grazers exhibiting higher nestedness and lower modularity in trophic networks.