How the environment shapes size: Body size variation in Osmia lignaria across ecoregions

Body size is a critical trait influencing the fitness, foraging range, offspring investment and overwintering survival in bees. In this study we examine how ecological variables and differences among ecoregions influence body size in the solitary bee, Osmia lignaria. Using a comprehensive dataset derived from museum specimens, we quantified body size using intertegualar span (IT span) measurements of individuals collected across a broad latitudinal gradient over multiple decades. By examining specimens from different ecoregions, we assessed the roles of climactic factors, and elevation in driving morphological variation through modeling and principle component analysis. Our results reveal significant correlations between body size and environmental gradients, as defined by ecoregion, suggesting that regional ecological pressure contributes to local adaption in O. lignaria. These finding provide insights into how environmental change may impact pollinator traits and their associated performance outcomes, including pollination services.