Abstract

One of the main consequences of globalization is the intensifi cation of biological introductions. Because of their negative impact on environments, the early detection and monitoring of introduced species through molecular approaches is gaining increased uptake. This study assembles 2,278 DNA barcode records to examine contemporary patterns of sequence variation in mitochondrial cytochrome c oxidase I (COI) in fi ve butterfl y species introduced to the Nearctic, with a focus on Pieris rapae Linnaeus (Lepidoptera: Pieridae) and Thymelicus lineola Ochsenheimer (Lepidoptera: Hesperiidae). Parameters of genetic diversity were low (i.e., h < 0.606, π < 0.0039) for Nearctic populations of all analyzed species. Those of P. rapae and T. lineola showed marked genetic differentiation from their source populations in the Palearctic. Haplotype distributions in their Nearctic populations exposed a starburst pattern with a few common haplotypes known from Palearctic, and infrequent haplotypes diverging from them at only one or two nucleotide sites. Some uncommon haplotypes were only found in the Nearctic suggesting they originated after invasion, while others also occur in the Palearctic. This study provides an example of genetic paradox of invasion, where species often rapidly expand their distribution and become dominant in the new habitat despite their depleted levels of sequence variation.