Plant diversity expands dietary niche breadth but facilitates dietary niche partitioning of co-occurring cattle and sheep

Abstract

Extensive research has elucidated the effects of plant diversity on small invertebrate consumers; however, the corresponding impacts on large generalist herbivores remain comparatively under-explored. This gap is particularly notable in the context of dietary variations across different species of sympatric large generalist herbivores. Given the prevalence and crucial role of domestic herbivores in grassland ecosystems, our study experimentally investigated the dietary variation, either in terms of partitioning or overlap, between co-occurring cattle and sheep across a range of plant diversity gradients. Our results demonstrated a significant expansion in the dietary niche breadth of cattle and sheep with increased plant diversity. However, the dietary expansion of the two large herbivore species with available plant diversity did not increase interspecific overlap. Rather, cattle and sheep mainly exploited the same resources in different proportions by this augmented plant diversity, leading to significantly reduced dietary niche overlap and thereby facilitating dietary partitioning between them. Our results underscore the critical role of preserving high plant diversity in facilitating dietary partitioning among large herbivores. This could enhance the synergistic effects of cattle and sheep grazing on plant communities. Our study also has important implications for the management of livestock grazing, suggesting that adopting mixed grazing of cattle and sheep in grasslands with high plant diversity could be more beneficial than in low-diversity grasslands.