Introduction ofGracilaria vermiculophylla(Rhodophyta, Gracilariales) to New England, USA: Estimated Arrival Times and Current Distribution

Abstract

Abstract The invasive Asiatic red alga Gracilaria vermiculophylla has recently spread rapidly around the globe. In the Northwest Atlantic, it was first collected in Virginia during 1998; in New England, it was first recorded from Narragansett Bay, Rhode Island in 2007. Until now, the specific dates of its introduction and current distribution in New England have been poorly understood. We employed a combination of field collections, evaluations of historical herbarium specimens, and molecular investigations (including mt-CO1 gene sequencing) to document its present distribution and approximate dates of introduction within New England. We found G. vermiculophylla at 18 of 24 Northwest Atlantic sites growing with native Gracilaria populations. Presently, it is recorded from Stamford, CT to Greenland, NH, with no populations known from five Maine sites where the native G. tikvahiae grows. Molecular screening of historical specimens revealed that G. vermiculophylla was collected from five sites in Massachuset...