Complementarity hypothesis assumes:
The complementarity hypothesis assumes that species contribute distinct traits or ecological functions. Differences in resource use, phenology, spatial occupation, or facilitation allow mixtures to capture resources more completely and perform better than would be expected if all species were functionally interchangeable. Ecosystem function can respond to diversity through niche partitioning, facilitation, insurance, or a sampling effect. Niche differences allow more complete resource use, asynchronous responses stabilize aggregate output, and high richness increases the chance of including a
Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation
