Effects of farmland consolidation in southern China on wild bee species composition, nesting location and body size variations

Traditional smallholding-dominated agricultural landscapes in Southern China are increasingly homogenized and consolidated, resulting in large mono-cropped fields and impoverished pollinator communities. The exact impact of this farmland consolidation on composition and functional traits of wild bee communities remains poorly understood. We studied these communities and functional traits in oilseed rape fields embedded in 18 agricultural landscapes located in Jiangxi Province, China, with 11 sites representing traditional (pre-consolidation) and the remaining 7 sites consolidated agricultural landscapes. The composition of wild bee assemblages was not differentiated into consolidated and traditional farmland communities. The mean body size of wild bee species similarly did not shows significant differences between consolidated and traditional farmland. The mean intraspecific body size for a dominant species, Lasioglossum proximatum, was larger in consolidated than traditional farmland, while individuals of co-dominant Eucera floralia showed no such differentiation. In consolidated farmland, the proportion of semi-natural habitat was positively linked to the abundance-based average interspecific body size of wild bee species. For abundance-based calculations, the proportion of aboveground nesting bee species was lower in consolidated landscapes than in traditional ones. Our study suggests that farmland consolidation might affect intraspecific composition, particularly in abundant small-bodied species. Above-ground nesting bees may require specific management interventions in consolidated agricultural landscapes to promote their persistence, which could take the form of semi-natural habitat patches introduced to fields that can also benefit the pollinator community more widely.