The Conservation of Common Carp Genetic Diversity in an Agroecosystem by Indigenous Farmers

The conservation of crop genetic diversity by farmers has been well studied, but little has been documented for farmed fish. Here, we show how indigenous farmers conserve the genetic diversity of a farmed fish species—the common carp (Cyprinus carpio), locally known as paddy field carp (PF-carp)—within the paddy ecosystem. The PF-carp have been cocultured with rice in paddy fields (i.e., rice-fish coculture) by multiethnic farmers for thousands of years in southwestern China. Although converging to a similar morphological shape as an adaptation to the paddy ecosystem, PF-carp have diverged into diverse phenotypes, displaying high genetic diversity and a distinct genetic structure pattern. Farmers from different ethnic groups showed distinct preferences for fish, resulting in phenotypic diversity and genetic variation. A large number of multiethnic farmers participated in fish propagation, thereby maintaining a high level of genetic diversity in PF-carp. Our results highlight the critical role of indigenous farmers in preserving local genetic diversity and mitigating genetic degradation.