Dual-Locus Metabarcoding Reveals Dry-Season Dietary Differentiation Between Elephants and Impalas in a South African Savanna.

Large herbivores in African savannas experience intense nutritional constraints during the dry season when declining forage quality intensifies competition for limited resources. Sympatric mixed feeders are therefore expected to differ in their use of forage resources, yet specific plant taxa underlying these dietary differences remain poorly resolved. Here, we used dual-locus DNA metabarcoding (rbcL and trnL) to characterise and compare dry-season diets of African elephants (Loxodonta africana) and impalas (Aepyceros melampus) in a semi-arid savanna ecosystem in South Africa. Despite substantial differences in body size and digestive physiology, dietary alpha diversity did not differ significantly between herbivores for either marker. In contrast, FOO-based Jaccard beta-diversity analyses revealed significant differences in dietary composition between species for both markers, with the strongest differentiation detected using trnL. Pianka's niche overlap index and relative read abundance analyses supported these patterns, showing lower overlap between species than within-species. Both herbivores relied heavily on woody taxa during the dry season. Elephants consumed a narrower assemblage dominated by browse genera such as Grewia, Dichrostachys and Vachellia, whereas impalas incorporated a more compositionally diverse mixture of woody, graminoid and forb taxa. Our findings demonstrate that dry-season dietary differentiation between these mixed feeders is associated less with differences in overall dietary breadth than with fine-scale taxonomic differences and contrasting use of woody, graminoid and forb resources. These results highlight the potential importance of maintaining taxonomic and growth-form heterogeneity in forage resources to support savanna herbivore assemblages under increasingly variable environmental conditions.