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 accarense was 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.Electronic supplementary materialThe online version of this article (doi:10.1007/s10530-014-0821-z) contains supplementary material, which is available to authorized users.

Not as clear as expected: what genetic data tell about Southern Hemisphere corellids (Ascidiacea: Phlebobranchia)

“…Sequences obtained from GenBank and BOLD System databases were included in the analysis for comparison and as outgroups (Stach and Turbeville 2002;Kurabayashi et al 2003;Monniot et al 2011;Pyo et al 2012;López-Legentil et al 2015;Turon et al 2016). Once aligned using the BioEdit program 7.0.5.3 (Hall 1999), sequences were collapsed into haplotypes; the number of polymorphic sites and haplotypes were calculated using the program DNAsp 6 (Rozas et al 2017).…”

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“…Ascidiella aspersa is also another widespread species that is introduced in many parts of the world. Moreover, it is assigned as an established alien species in the Mediterranean Sea (López-Legentil et al, 2015;Zenetos et al, 2010).…”

Biological activity of extract from Styela plicata and Ascidia mentula (Ascidiacea)

“…S. plicata is an introduced species which is dominant in harbour areas and in zones with highly modified substrates, a low rate of water renewal and excess silting and suspended matter. 23 It mainly colonized the mussel farm structures in the inner part of the Lake Faro, with high benthic production and related space completion. By contrast, the native A. mentula, colonizing both natural rocks in the outer zone of the bay and vertical walls of ports, is generally absent from internal harbour areas with low water movement.…”