Elevation and grassland cover shape natural enemy communities in the Kenyan maize crops

Résumé fourni par la source

Abstract Natural enemies, including arthropod predators and parasitoids, provide essential pest control services in agricultural systems by reducing pest populations. However, studies examining how natural enemies respond to environmental gradients, such as elevation and grass cover, are limited in sub-Saharan Africa. This study investigates the effect of elevation (1150–1970 m above sea level) and grassland cover in the surrounding landscape (2–30%) on natural enemy communities in maize fields in western Kenya over two consecutive sampling seasons. We selected maize fields along gradients of elevation and percentage of grassland and conducted field surveys using pitfall traps to assess the diversity and composition of natural enemies. Natural enemy diversity, richness, evenness, abundance and community composition were compared across gradients using Generalised Linear Mixed Models and Non-Metric Multidimensional Scaling. Across gradients, ants were the most abundant predator group. Lower elevations supported natural enemy communities with higher evenness, while higher elevations were dominated by Myrmicaria ants. Grassland cover had limited overall effects, with a non-significant but positive association with species richness. Notably, community composition shifted along the elevational gradient, with Myrmicaria ants being less dominant < 1600 masl. Their dominance at high elevations, where grass cover is lower, may reduce overall pest control resilience, as low evenness and reliance on a single genus diminish functional redundancy. This underscores the need for integrated pest management strategies that consider multiple environmental variables. Overall, our findings highlight the importance of environmental gradients in shaping natural enemy biodiversity in agricultural fields with implications for pest control in western Kenya.

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