Intraspecific crop diversity for enhanced crop pollination success. A review

Interspecific crop diversity (e.g., intercropping) has been documented to promote sustainability in agroecological systems with benefits for pollination services and insect pollinators. These benefits may also be extended to intraspecific crop diversity (e.g., cultivation of multiple genotypes or cultivars in a production space), but no review to date has examined the benefits of intraspecific crop diversity for pollination and pollinator communities. While mixing cultivars is necessary and a widespread practice for pollination of self-incompatible or male-sterile crops, it is not as widespread for other crop species. However, many other crops have shown reduced yield quantity or quality with self-fertilization due to partial self-sterility, early acting inbreeding depression, and xenia. These crops could thus experience increased production in diverse cultivar mixtures. Cultivar mixtures could also benefit pollinator communities through providing complementary and temporally consistent floral resources, with cascading effects on pollination services. However, successfully implementing cultivar mixtures requires an understanding of how cultivar identity and arrangement affect successful cross-pollination. In this review, we describe the potential benefits of increased intraspecific crop diversity for optimal pollination and pollinator populations across insect-pollinated crops. Additionally, we explore how research advances in cultivar characteristics and insect pollinator behavior and movement, as well as crop pollen flow, can inform cultivar mixtures and spatial arrangements. We find evidence that mixing cultivars, even in self-compatible crops, improves pollination outcomes and yields. Additionally, given insect pollinator behavior and pollen flow, such mixing must occur at relatively small spatial scales. Furthermore, cultivar diversity could ensure successful pollination and resource production for pollinators under extreme weather events. We also discuss costs and benefits of diverse cultivar mixtures from a grower’s perspective and offer suggestions for future research including translating findings within the context of farming systems so that recommendations are practical and achievable.