title: Harbor networks as introduction gateways: contrasting distribution patterns of native and introduced ascidians.
abstract: Harbors and marinas are well known gateways for species introductions in marine environments but little work has been done to ascertain relationships between species diversity, harbor type, and geographic distance to uncover patterns of secondary spread. Here, we sampled ascidians from 32 harbors along ca. 300 km of the NW Mediterranean coast and investigated patterns of distribution and spread related to harbor type (marina, fishing, commercial) and geographic location using multivariate techniques. In total, 28 ascidians were identified at the species level and another 9 at the genus level based on morphology and genetic barcoding. Eight species were assigned to introduced forms, 15 were given native status and 5 were classified as cryptogenic.Aplidium accarensewas reported for the first time in the Mediterranean Sea and was especially abundant in 23 of the harbors. Introduced and cryptogenic species were abundant in most of the surveyed harbors, while native forms were rare and restricted to a few harbors. Significant differences in the distribution of ascidians according to harbor type and latitudinal position were observed. These differences were due to the distribution of introduced species. We obtained a significant correlation between geographic distance and ascidian composition, indicating that closely located harbors shared more ascidian species among them. This study showed that harbors act as dispersal strongholds for introduced species, with native species only appearing sporadically, and that harbor type and geographic location should also be considered when developing management plans to constrain the spread of non-indigenous species in highly urbanized coastlines.
authors.affiliation: Department of Biology and Marine Biology, Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC 28409 USA.
authors.forename: Susanna
authors.initials: S
authors.lastname: López-Legentil
authors.affiliation: Departament de Biologia Animal, Universitat de Barcelona (UB), Diagonal Avenue 643, 08028 Barcelona, Spain.
authors.forename: Miquel L
authors.initials: ML
authors.lastname: Legentil
authors.affiliation: Department of Biology and Marine Biology, Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC 28409 USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Erwin
authors.affiliation: Center for Advanced Studies of Blanes (CEAB-CSIC), Accés Cala S. Francesc 14, 17300 Blanes, Girona, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Turon
keywords: Artificial substrates; Barcoding; Distribution; Diversity; Introduced species; Tunicates