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Este artículo contiene 6 páginas, 1 figura. ; Phylogeography is an integrative discipline that aims to understand the geographic ordination of genotypes. In recent decades, phylogeographic approaches have been used to enhance our understanding of both biogeography and landscape genetics across a variety of spatial and temporal scales. By definition, species studied using these approaches need to meet certain assumptions (e.g. mutation and drift need to be at equilibrium). However, artificially dispersed species (i.e. non-indigenous, naturalised and invasive species) often do not comply with these assumptions. Thus, the use of phylogeographic approaches to study these species may lead to erroneous interpretations. Considering that self-denominated phylogeographic studies of invasive species have proliferated in recent years and that genomic tools are now more accessible than ever before, kick starting this debate is particularly timely. We argue herein that invasion scientists must carefully use phylogeographic approaches when studying genomic data obtained from the introduced range. In addition, the assumptions of these phylogeographic approaches need to be explicitly considered when interpreting genomic patterns of invasive species. Finally, we suggest abandoning the use of the term 'phylogeography' for describing geographically contextualized genomic data from the introduced range to avoid both terminological and methodological confusion. ; The ideas developed in this opinion note were partly conceived during the development of the project CTM2017-88080 (MCIU/AEI/FEDER/UE) from the Spanish Government. ; Peer reviewed

15 páginas, 5 figuras, 3 tablas. ; Cryptic diversity represents a major challenge to the accurate assessment of biodiversity, but the combined use of genetic and morphological analyses has proven to be a powerful approach to detect it. This is especially important for groups for which genetic information is not yet available. Here, we studied the highly conspicuous habitatforming Pyura stolonifera species complex (Tunicata), which, as has recently been revealed, shows surprising levels of cryptic diversity, but whose systematics and biogeographical patterns in Australasia nonetheless remain poorly understood. We first present detailed taxonomic information of all the species associated with the P. stolonifera species complex. We then proceed to describe the results of an exhaustive survey that included south-east Australia, Tasmania, and New Zealand. Subsequently, we present morphological and mitonuclear genetic analysis of two unresolved lineages that comprise the species Pyura praeputialis and a species that is formally described here (Pyura doppelgangera sp. nov.). Although the ranges of these two species overlap on mainland Australia, we found no sites at which both species live in sympatry, and there was no morphological or genetic evidence of hybridization. Taken together, the present study illustrates the usefulness of a combined morphogenetic approach in unravelling overlooked marine diversity in a relatively well-studied region. ; The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIOF-GA-2009-254634 to M. R. and from the Australian Research Council (DP110101275 to Beheregaray, Möller & Waters). ; Peer reviewed

3 páginas, 1 tabla. ; The gorgonian Paramuricea clavatais a benthic organism often included in conservation management plans since it creates complexity in the ecosystems and is extremely vulnerable to disturbances. Eight microsatellite markers isolated from an enriched genomic library were characterized in a total of 50 individuals from two northwestern Mediterranean populations. All loci were polymorphic and the number of alleles per locus ranged between 2 and 14. Significant genetic differentiation was observed between populations. The polymorphic markers presently isolated will allow for the assessment of the spatial genetic structure between and within populations of this umbrella species of the Mediterranean Sea. ; This research was supported by projects 119/2003 and CTM2007-66635 (CICYT) from the Spanish Government. ; Peer reviewed

11 Páginas ; 3 Figuras ; 3 Tablas ; 1 Apéndice ; The spread of non-indigenous species into new marine habitats represents an increasing threat to global diversity. Genetic techniques provide basic understanding of the invasion processes. The ascidian Microcosmus squamiger is considered to be native to Australia, having been spread worldwide via transoceanic vessels. It has successfully invaded artificial and natural habitats where it has become a pest. We studied phylogeography and genetic structure of 12 M. squamiger populations, including samples from its native range (Australia) and introduced populations from the Indian, Pacific, and Atlantic oceans, as well as the Mediterranean Sea. We amplified 574 bp of the mitochondrial COI gene in 258 individuals and found a total of 52 haplotypes. A haplotype tree revealed two main groups of haplotypes. The relative frequency of each group of haplotypes, multidimensional scaling, and analysis of molecular variance showed important differences between the western Australia localities and the remaining ones (eastern Australia and introduced populations). Furthermore, we found that the colonization of the different areas by M. squamiger has not occurred independently, as many introduced populations shared some low frequency alleles. A nested clade analysis showed a global pattern of restricted gene flow with isolation by distance, although we found episodes of long-distance dispersal in some clades. A contiguous range expansion was detected between Australian populations. We conclude that M. squamiger is native to Australia and has most likely expanded its range of distribution sequentially through worldwide shipping, especially from the harbours of the more populated eastern Australia. In introduced populations, we found a high genetic diversity which suggests enhanced invasive potential. Consequently, there is a need to control this species, as it outcompetes local biota and is an economic threat. ; This research was funded by projects CTM2004-05265, CGL2006-13423, and CTM2007-66635 of the Spanish Government and a FPU scholarship to M. R. from the Spanish 'Ministerio de Educación y Ciencia'. ; Peer reviewed

14 Páginas ; 10 Figuras ; 1 Tabla ; Marine introductions are a serious threat for biodiversity, especially in seas where shipping is intensive. Microcosmus squamiger is a widespread marine invader that can alter native biota and it is therefore imperative to understand its biology and ecology. We studied the population dynamics and reproductive cycles of M. squamiger over a 2-year period, as well as its settlement and colonization patterns, in a north-western Mediterranean (NE Spain) locality where M. squamiger has been introduced. All biological parameters showed a strong seasonal pattern that peaked in summer with a major spawning episode at the end of summer. Sizefrequency histograms indicated a 2-year cycle. Colonization experiments suggested that M. squamiger recruitment mortality is high and requires a well structured community. In addition, we monitored the abundance of the native predator Thais haemastoma, which showed a significant positive correlation with M. squamiger biomass, indicating its potential usefulness as a biological control. ; This study was funded by project CTM2007-66635 of the Spanish Government. ; Peer reviewed

10 Páginas ; 3 Figuras ; 5 Tablas ; Studies examining the eVects of invasive species have focussed traditionally on the direct/lethal eVects of the invasive on the native community but there is a growing recognition that invasive species may also have non-lethal eVects. In terrestrial systems, non-lethal eVects of invasive species can disrupt early life-history phases (such as fertilisation, dispersal and subsequent establishment) of native species, but in the marine environment most studies focus on adult rather than early life-history stages. Here, we examine the potential for an introduced sessile marine invertebrate (Styela plicata) to exert both lethal and non-lethal eVects on a native species (Microcosmus squamiger) across multiple early life-history stages. We determined whether sperm from the invasive species interfered with the fertilisation of eggs from the native species and found no eVect. However, we did Wnd strong eVects of the invasive species on the post-fertilisation performance of the native species. The invasive species inhibited the settlement of native larvae and, in the Weld, the presence of the invasive species was associated with a tenfold increase in the post-settlement mortality of the native species, as well as an initial reduction of growth in the native. Our results suggest that larvae of the native species avoid settling near the invasive species due to reduced postsettlement survival in its presence. Overall, we found that invasive species can have complex and pervasive eVects (both lethal and non-lethal) across the early life-history stages of the native species, which are likely to result in its displacement and to facilitate further invasion. ; This project was funded by projects DPO666147 of the Australian Research Council, and CTM2007- 66635 and PIE 200730I026 of the Spanish Government ; Peer reviewed

16 páginas, 4 figuras, 4 tablas. ; Following the introduction to a new area (preborder dispersal), post-border processes determine the success in the establishment of non-indigenous species (NIS). However, little is known on how these post-border processes shape the genetic composition of NIS at regional scales. Here, we analyse genetic variation in introduced populations along impacted coastlines to infer demographic and kinship dynamics at the post-border stage. We used as a model system the ascidian species Microcosmus squamiger that has been introduced worldwide. This species can colonize and grow fast on man-made artificial structures, impacting activities such as mariculture. However, it can also establish itself on natural substrates, thus altering natural communities and becoming an ecological problem. We genotyped 302 individuals from eight populations established on natural and artificial substrates in the north-western Mediterranean Sea, using six microsatellite loci. We then compared the resulting genotypes with those found within the native range of the species. We found high levels of genetic diversity and allelic richness in all populations, with an overall deficit of heterozygotes. Autocorrelation analyses showed that there was no withinpopulation genetic structure (at a scale of tens of metres); likewise, no significant differentiation in pairwise comparisons between populations (tens of kilometres apart) and no isolation-by-distance pattern was found. The results suggest that M. squamiger has a natural capacity for high dispersal from one patch of hard substrate to another and no differences whatsoever could be substantiated between natural and artificial substrates. Interestingly, two groups of genetically differentiated individuals were detected that were associated with the two ancestral source areas of the worldwide expansion of the species. Individual assignment tests showed the coexistence of individuals of these two clusters in all populations but with little interbreeding among them as the frequency of admixed individuals was only 15 %. The mechanism responsible for maintaining these genetic pools unmixed is unknown, but it does not appear to compromise post-border colonization of introduced populations. ; This research was funded by projects CTM2010-22218 of the Spanish Government, BIOCON08-187 of the FBBVA and PIE 200730I026 of the Spanish Research Council (CSIC). Funding to M. R. came from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no PIOF-GA-2009- 254634. V. O. was supported by a FPU PhD scholarship (AP2008/ 04209) from the Spanish Ministerio de Educacio´n. The authors are part of the research groups 2009SGR-636 and 2009SGR-484 of the Generalitat de Catalunya (Spain). ; Peer reviewed

10 páginas, 4 tablas, 4 figuras ; The existence of globally-distributed species with low dispersal capabilities is a paradox that has been explained as a result of human-mediated transport and by hidden diversity in the form of unrecognized cryptic species. Both factors are not mutually exclusive, but relatively few studies have demonstrated the presence of both. Here we analyse the genetic patterns of the colonial ascidian Diplosoma listerianum, a species nowadays distributed globally. The study of a fragment of a mitochondrial gene in localities worldwide revealed the existence of multiple cryptic species. In addition, we found a complex geographic structure and multiple clades occurred in sympatry. One of the species showed strong population structure irrespective of geographical distances, which is coherent with stochastic dispersal linked to human transport. The present study shows the complexity of discerning the role of cryptic diversity from human-driven range shifts worldwide, as well as disentangling the effects of natural and artificial dispersal. ; This research was supported by the Spanish Ministry of Science (project CTM2010-22218, BENTHOMICS, and a 'Juan de la Cierva' contract to R.P.-P.), by the European Union Seventh Framework Programme FP7/2007–2013 (project 287844, COCONET, and grant agreement PIOF-GA-2009-254634 to M.R.), and by the Chilean Government (CONICYT agreement 80122006 to X.T.). ; Peer reviewed

9 Páginas ; 4 Figuras ; 1 Tabla ; 1. Mothers must balance the fecundity costs of increasing propagule size with the fitness benefits of increased propagule performance, and the propagule size-performance relationship is crucial for determining this trade-off. 2. While many studies have examined the propagule size-performance relationship in individual life-history stages, very few have examined the relationship between propagule size and performance across multiple life-history stages despite the ubiquity of complex life cycles. 3. We examined the consistency of the propagule size-performance relationship across several life-history stages in the marine invertebrate Microcosmus squamiger (Ascidiacea). 4. Propagule size had effects in some life-history stages and not others: larger propagules hatched sooner as larvae and grew more as juveniles in the field. On the other hand, propagule size had no effect on cell cleavage rates, larval swimming time or post-metamorphic survival in the field. 5. The effects of propagule size on juvenile size were persistent – juveniles that came from larger propagules were still larger than juveniles that came from smaller propagules after 11 weeks in the field. 6. We found no evidence of conflicting selection pressures on propagule size among life-history stages. Rather, in this species at least, the selection on propagule size at both the larval and juvenile stage appeared to favour the production of larger propagules. Nevertheless, the slope of the relationship between propagule size and performance was highly variable among life-history stages. 7. The effects of propagule size across multiple life-history stages are determined by the strength of selection pressures, which can be highly variable in organisms with complex life-cycles. ; Funding was obtained from project DPO6666147 of the Australian Research Council to DJM, the project CTM2007-66635 of the Spanish Government to XT. MR was supported by a travel grant from the Spanish 'Ministerio de Educacio´n y Ciencia' during his stay at the University of Queensland. GMD was supported by a Brazilian government grant from CAPES. ; Peer reviewed

17 páginas, 4 figuras ; Over the last 15 years studies on invasion genetics have provided important insights to unravel cryptic diversity, track the origin of colonizers and reveal pathways of introductions. Despite all these advances, to date little is known about how evolutionary processes influence the observed genetic patterns in marine biological invasions. Here, firstly we review the literature on invasion genetics that include samples from European seas. These seas constitute a wide array of unique water masses with diverse degrees of connectivity, and have a long history of species introductions. We found that only a small fraction of the recorded introduced species has been genetically analysed. Furthermore, most studies restrict their approach to describe patterns of cryptic diversity and genetic structure, with the underlying mechanisms involved in the invasion process being largely understudied. Secondly, we analyse how genetic, reproductive and anthropogenic traits shape genetic patterns of marine introduced species. We found that most studies reveal similar genetic diversity values in both native and introduced ranges, report evidence of multiple introductions, and show that genetic patterns in the introduced range are not explained by taxonomic group or reproductive strategy. Finally, we discuss the evolutionary implications derived from genetic patterns observed in non-indigenous species. We identify different scenarios that are determined by propagule pressure, phenotypic plasticity and pre-adaptation, and the effects of selection and genetic admixture. We conclude that there is a need for further investigations of evolutionary mechanisms that affect individual fitness and adaptation to rapid environmental change. ; Funding was provided by the European Union FP7 project COCONET (7th PM, Grant agreement #287844) and a number of other sources. F.Vi. acknowledges the HiFlo (ANR-08- BLAN-0334) and HySea (ANR-12-BSV7-0011) ANR programmes. X.T. is grateful to the Spanish Ministry of Science projects CTM2010-22218 and CTM2013-48163. The publication of this paper was supported by CONISMA, the Italian National Interuniversity Consortium for Marine Sciences, which received funding from the European Community's Seventh Framework Programme (FP7/2007- 2013) for the project VECTORS (Vectors of Change in Oceans and Seas Marine Life, Impact on Economic Sectors, Grant agreement #266445, http://www.marine-vectors.eu). This paper stems from the International workshop MOLTOOLS (Molecular Tools for Monitoring Marine Invasive Species), held in Lecce, Italy, in September 2012. ; Peer reviewed

The European Union's Marine Strategy Framework Directive (MSFD) aims to adopt integrated ecosystem management approaches to achieve or maintain "Good Environmental Status" for marine waters, habitats and resources, including mitigation of the negative effects of non-indigenous species (NIS). The Directive further seeks to promote broadly standardized monitoring efforts and assessment of temporal trends in marine ecosystem condition, incorporating metrics describing the distribution and impacts of NIS. Accomplishing these goals will require application of advanced tools for NIS surveillance and risk assessment, particularly given known challenges associated with surveying and monitoring with traditional methods. In the past decade, a host of methods based on nucleic acids (DNA and RNA) analysis have been developed or advanced that promise to dramatically enhance capacity in assessing and managing NIS. However, ensuring that these rapidly evolving approaches remain accessible and responsive to the needs of resource managers remains a challenge. This paper provides recommendations for future development of these genetic tools for assessment and management of NIS in marine systems, within the context of the explicit requirements of the MSFD. Issues considered include technological innovation, methodological standardization, data sharing and collaboration, and the critical importance of shared foundational resources, particularly integrated taxonomic expertise. Though the recommendations offered here are not exhaustive, they provide a basis for future intentional (and international) collaborative development of a genetic toolkit for NIS research, capable of fulfilling the immediate and long term goals of marine ecosystem and resource conservation.