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.

中文翻译：

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港口网络作为引进门户：本地和引进海生动物的分布模式对比。

港口和码头是在海洋环境中引入物种的众所周知的门户，但很少开展工作来确定物种多样性，港口类型和地理距离之间的关系以发现二次扩散的模式。在这里，我们从大约32个港口采样了海生动物。在西北地中海沿岸300公里处，使用多元技术研究了与港口类型（码头，渔业，商业区）和地理位置有关的分布和扩散方式。根据形态学和遗传条形​​码，总共在物种水平上鉴定出28个海鞘，在属水平上鉴定出另外9个。将8个物种指定为引入的形式，将15个物种定为原始身份，将5个物种归为隐源性。在地中海首次报道了螨，在23个港口中尤为丰富。在大多数被调查的港口中，引入的和隐源性物种丰富，而本地形式却很少，并且仅限于少数港口。根据海港类型和纬度位置，观察到海鞘分布有显着差异。这些差异是由于引进物种的分布所致。我们获得了地理距离与海平面组成之间的显着相关性，表明位置靠近的港口在它们之间共享了更多的海平面物种。这项研究表明，港口是引进物种的传播据点，而本地物种只是偶尔出现，