Figure 1. Bayesian tree of COI sequences.

Posterior probabilities (> 0.5) are shown at nodes. Squares at branch tips, within four phylogroups – Watersipora arcuata, W. subtorquata clades A and B, and W. n. sp. – indicate an introduced haplotype on the Californian coast. Haplotypes found in other areas are indicated: Washington state (Pacific US); AU, Australia; Fl, Florida (Atlantic, US); BR, Brazil; Ha, Hawaii (O'ahu); NZ, New Zealand (Wellington); UK (southern England and Channel Islands); FR, France. Watersipora colonies have uniform zooids. Typical dimensions were determined from multiple colonies in different COI groups, providing a stereotyped zooid appearance (see Figure 4).