View article

Surveys of genetic structure of introduced populations of nonindigenous species may reveal the source(s) of introduction, the number of introduction events, and total inoculum size. Here we use the mitochondrial cytochrome c oxidase subunit 1 (COI) gene to explore genetic structure and contrast invasion histories of two ecologically similar and highly invasive colonial ascidians, the golden star tunicate Botryllus schlosseri and the violet tunicate Botrylloides violaceus, in their global and introduced North American ranges. Haplotype and nucleotide diversities for B. schlosseri were significantly higher than for B. violaceus both globally (h = 0.872; π = 0.054 and h = 0.461; π = 0.007, respectively) and in their overlapping North American ranges (h = 0.874; π = 0.012 and h = 0.384; π = 0.006, respectively). Comparative population genetics and phylogenetic analyses revealed clear differences in patterns of …