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13 páginas, 6 figuras, 6 tablas. ; We explored temporal patterns of genetic diversity and spatial genetic structure of the recently introduced ascidian Perophora japonica Oka, 1927 in Europe. A fragment of the mitochondrial gene cytochrome c oxidase subunit I (COI) was sequenced for 291 colonies of one population in Plymouth, UK, which was monitored for 9 yr after its initial discovery. A total of 238 colonies from 12 localities were also sequenced for population structure analyses. The temporal monitoring of the Plymouth population showed a progressive loss of genetic diversity over time attributable to a strong initial bottleneck followed by genetic drift and/or selection. Population genetic structure was consistent with the historical records of this introduction, which probably originated from oyster farming activities in France, from where the species spread to the UK and Spain. Only one population in France displayed high levels of genetic diversity, and most of the remaining populations presented very low variability. In addition, significant differentiation in terms of allele frequencies was detected between some populations. P. japonica has suffered a loss of genetic diversity in both space and time since its introduction, but this did not prevent its expansion. Accidental human transport is the most likely mechanism of spread within the introduced range. Asexual propagation modes and chimerism in this species may play an important role in introduction events. The genetic data presented here can contribute to the design of more efficient management methods for this and similar introduced species. ; This research was supported by a postdoctoral grant from foundation FUNDAME and a 'Beatriu de Pinós' contract (Comissionat per a Universitats i Recerca from Departament d'Innovació, Universitats i Empresa, Generalitat de Catalunya) to R.P.P. Funding was provided by project CTM2010-22218 (BENTHOMICS) of the Ministry of Science from the Spanish Government, the EU FP6 Network of Excellence 'Marine Genomics', the NERC Oceans 2025 programme and the AXA Research Fund 'Marine Aliens and Climate Change' project. ; Peer reviewed

11 Páginas ; 3 Figuras ; 3 Tablas ; The Order Stolidobranchiata comprises the families Pyuridae, Styelidae and Molgulidae. Early molecular data was consistent with monophyly of the Stolidobranchiata and also the Molgulidae. Internal phylogeny and relationships between Styelidae and Pyuridae were inconclusive however. In order to clarify these points we used mitochondrial and nuclear sequences from 31 species of Styelidae and 25 of Pyuridae. Phylogenetic trees recovered the Pyuridae as a monophyletic clade, and their genera appeared as monophyletic with the exception of Pyura. The Styelidae, on the other hand, appeared as a paraphyletic group split into several clades. One of them was formed by solitary oviparous species, of which the Pyuridae were a sister group. A second clade included the colonial genera Botryllus, Botrylloides and Symplegma. The remaining colonial and solitary genera formed several poorly resolved clades. One of the more species genus, Polycarpa, was shown to be polyphyletic, and the species Styela plicata grouped into two genetically distant clades suggesting the existence of two cryptic species. The internal phylogeny of Styelidae has bearings on the origin of coloniality in this family. We suggest to abandon the traditional division of colonial forms into social and compound species and use instead the categories of aggregated colonies that do not have common vascular systems, and integrated colonies, that do possess such systems. Our molecular results indicate that there have been several independent acquisitions of coloniality in the Styelidae, and that viviparity may be a pre-adaptation for a colonial life-style. ; This research was supported by a postdoctoral grant from the Spanish foundation ''Fundación Alfonso Martín Escudero (FUNDAME)", a FCT postdoctoral fellowship from the Portuguese Government (SFRH/BPD/41055/2007) and by project CTM2007-66635 of the Spanish Government and project 2007301026 (CSIC). This represents contribution no. 284 from the Ecology and Genetics Group at the University of Wollongong. ; Peer reviewed

Este artículo contiene 13 páginas, 4 figuras, 2 tablas. ; Molecular tools have been extensively used in recent decades to examine biological invasion processes, and are increasingly being adopted as efficient tools to support non-indigenous species surveys, notably through barcoding approaches, i.e., the use of a reference sequence specific to a given species to validate its identification. The technique is easy to use but requires reliable reference sequences to be available in public databases. In addition, the increasing discovery of cryptic species in marine taxa may complicate taxonomic assignment. We illustrate these two issues in the ascidian genus Botrylloides, in which at least three global marine invaders have been recognized, including B. violaceus and B. diegensis. We obtained COI sequences from >750 colonies of Botrylloides spp. sampled in W Europe or provided by expert colleagues from other regions. Phylogenetic trees clearly distinguished our targeted taxa [i.e., B. violaceus, B. diegensis and B. leachii (native)]. They also revealed another discrete lineage apparently related to a recently described eastern Mediterranean species. By examining public databases, we found sequences of B. diegensis erroneously assigned to B. leachii. This observation has major implications as the introduced B. diegensis can be misidentified as a putatively native species. We also checked published sequences of the genus Botrylloides in the Mediterranean Sea, complemented with new samples. Based on our custom reference database, all published sequences of B. leachii corresponded to B. diegensis, although this NIS has hardly been reported at all in the Mediterranean region. Such database errors are unfortunate, as the barcoding approach is a powerful tool to identify the recognized Botrylloides species currently present in European seas. This is of particular importance because a trait often used during field assessment, i.e., single-color vs. two-color colonies, is misleading to distinguish B. violaceus and B. diegensis respectively: a substantial proportion of the single-color morph are actually B. diegensis in both the Mediterranean Sea and the English Channel. Altogether, this study exemplifies the advantages and disadvantages of molecular barcoding in NIS surveys and studies. The limitations that were identified are all easy to resolve once proper vouchers and collections are set up. ; This work was part of the Interreg IVA project 'Marinexus' financed under the European Regional Development Fund. And also received further support from the AquaNIS2.0 project funded by the Fondation TOTAL, and from project CTM2017- 88080 (MCIU/AEI/FEDER/UE) of the Spanish Government. ; Peer reviewed

The European Union (EU) has recently published its first list of invasive alien species (IAS) of EU concern to which current legislation must apply. The list comprises species known to pose great threats to biodiversity and needs to be maintained and updated. Horizon scanning is seen as critical to identify the most threatening potential IAS that do not yet occur in Europe to be subsequently risk assessed for future listing. Accordingly, we present a systematic consensus horizon scanning procedure to derive a ranked list of potential IAS likely to arrive, establish, spread and have an impact on biodiversity in the region over the next decade. The approach is unique in the continental scale examined, the breadth of taxonomic groups and environments considered, and the methods and data sources used. International experts were brought together to address five broad thematic groups of potential IAS. For each thematic group the experts first independently assembled lists of potential IAS not yet established in the EU but potentially threatening biodiversity if introduced. Experts were asked to score the species within their thematic group for their separate likelihoods of i) arrival, ii) establishment, iii) spread, and iv) magnitude of the potential negative impact on biodiversity within the EU. Experts then convened for a 2-day workshop applying consensus methods to compile a ranked list of potential IAS. From an initial working list of 329 species, a list of 66 species not yet established in the EU that were considered to be very high (8 species), high (40 species) or medium (18 species) risk species was derived. Here, we present these species highlighting the potential negative impacts and the most likely biogeographic regions to be affected by these potential IAS.