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Abstract
Spatial diversity indicators may serve policymakers as they seek to manage crop genetic
diversity and externalities associated with diffusion of some genetically modified crops. This
paper adapts ecological indices of spatial diversity to area distributions of modern wheat
varieties in contrasting production systems of Australia and China. The variation in three
concepts of spatial diversity—richness, abundance, and evenness—is explained using
Zellner’s seemingly unrelated regression (SUR). Determinants of wheat diversity differ by
concept, but include variety traits other than yield potential, environmental factors, and
policies affecting the supply of varieties, research spill-ins, and market liberalization.