Diversity and disease: evidence for the monoculture effect beyond agricultural systems

Abstract

Human activities are greatly reducing the genetic diversity of species worldwide. Given the prediction that parasites better exploit less diverse host populations, many species could be vulnerable to disease outbreaks. However, the widespread nature of the monoculture effect remains unclear outside agricultural systems. We conducted a meta-analysis of 22 studies, obtaining a total of 66 effect sizes, to directly test the biological conditions under which host genetic diversity limits infectious disease in populations. Overall, we found broad support for the monoculture effect across host and parasite species. The effect was independent of host range, host reproduction, parasite diversity, and the method by which the monoculture effect was recorded. Conversely, we found that parasite functional group, virulence, and empirical environment matters. Together, these results highlight the general susceptibility of genetically homogenous populations to infection. Consequently, this phenomenon could become increasingly common and alarming for at-risk populations due to human-driven declines in genetic diversity and shifts in parasite distributions.