Urbanization-associated range expansion genetically homogenizes a butterfly species.

Human-induced environmental change and globalization facilitate biological invasions, which can lead to the displacement of native species by non-native ones. 1,2,3,4 Analogously, biodiversity loss may occur within species when habitat modifications facilitate the expansion of a specific population's range, leading to genetic admixture with native local populations. We demonstrate such intraspecific loss in population-level diversity in the Southern Small White (Pieris mannii), an originally sedentary butterfly 5 that recently expanded its range across Central Europe due to urbanization. 6,7,8 Using genome-wide markers from historical museum specimens and contemporary samples, we identify a distinct population initiating this expansion and reveal the genetic homogenization of native local populations by admixture with the expansive one. Our study illustrates how human-made environmental change can simultaneously benefit a species by permitting range expansion and drive cryptic biodiversity loss through the genetic homogenization of conspecific populations. • Range expansion in Pieris mannii butterflies is driven by a distinct population • This population now mixes with formerly isolated local populations • Population mixing causes loss of evolutionary distinctiveness within this species The butterfly Pieris mannii recently expanded its range across Central Europe in response to urbanization. Comparing DNA sequence data from museum and contemporary specimens, Blattner et al. show that this expansion is driven by a distinct lineage and that the mixing of this lineage with local ones results in within-species genetic homogenization. [ABSTRACT FROM AUTHOR]