Environmental gradients shape climate adaptive phenotypes in Muscovy ducks in Benin with implications for adaptation policy.

Climate change threatens livestock-dependent livelihoods across sub-Saharan Africa, yet National Adaptation Programmes of Action (NAPAs) and Nationally Determined Contributions (NDCs) rarely incorporate animal genetic resource management despite explicit mandates under the Convention on Biological Diversitys Global Plan of Action for Animal Genetic Resources. This study addresses this policy gap by investigating how environmental gradients shape phenotypic adaptation in Muscovy duck (Cairina moschata) populations across Benins three agroecological zones, generating evidence to inform climate-responsive livestock policy. We surveyed 505 farmers and characterized 1,300 ducks across dry (Temperature-Humidity Index [THI]: 70-74), sub-humid (THI: 74-78), and humid (THI: 78-82) zones. Climate analysis confirmed accelerating thermal stress (+0.38 degrees C per decade in humid zones), exceeding IPCC West African projections and threatening Sustainable Development Goal 2 (Zero Hunger) targets. Principal component analysis revealed zone-specific phenotypic clustering (57.9% variance explained), with thermoregulatory traits showing coordinated adaptation: body volume-surface ratios 42.7% lower in humid zones (p = 0.002), limb proportions 72.7% higher (p < 0.001), and white feather coverage 31.3% greater (p = 0.019). Reproductive performance declined significantly along the thermal gradient (lifetime production: 40.7 vs. 37.1 eggs; p < 0.001), quantifying climate-driven productivity losses relevant to national food security assessments. Phenotype-climate associations demonstrated that locally adapted variants (black-white pied in dry zones; white-black-green pied in humid zones) maintain superior fitness under native conditions, providing critical evidence for the breed-for-environment approach advocated by FAOs Climate-Smart Agriculture framework. These findings provide an empirical foundation for incorporating animal genetic resource conservation into Benins NDC implementation, ECOWAS regional livestock strategies, and the African Unions Comprehensive Africa Agriculture Development Programme (CAADP) climate resilience targets.