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Invasive alien species pose a serious threat to the integrity and function of natural ecosystems. Understanding how these invaders alter natural communities is therefore an important aspect in predicting the likely future outcomes of biological invasions. Many studies have documented the consequences of invasive alien species on native community structure, through the displacement and local extinction of native species. However, sampling methods and intensities are rarely standardised across such studies, meaning that it is not clear whether differences in response among native communities to the same invader species are due to biological differences between the invaded regions, or differences in the methodologies used. Here we use a matched sampling methodology to compare the effects of the Argentine ant (Linepithema humile Mayr) on native ant community assemblages in two distinct biogeographical regions that share similar ecologies: Girona (Spain) and Jonkershoek Nature Reserve (South Africa). We found a strong negative association between L. humile presence and native ant species richness within both geographic regions. However, the effects differed between the two study regions: in Girona, a single native ant species (Plagiolepis pygmaea) persisted in invaded sites; by contrast, substantially more native ant species persisted at invaded sites in Jonkershoek Nature Reserve. In addition, in Jonkershoek Nature Reserve, the abundance of certain native species appeared to increase in the presence of L. humile. This study therefore demonstrates the potential variable effects of an invasive species in contrasting locations within different biogeographical regions. Future work should explore the causes of this differential resistance among communities and expand standardised sampling approaches to more invaded zones to further explore how local biotic or abiotic conditions of a region determine the nature and extent of impact of L. humile invasion on native ant communities This work was funded by grants and awards from the Natural Environmental Research Council (NERC) Case Studentship awarded to SS, JB and RN (NE/K007076/1); COST Action TD1209 (ECOST-STSM-TD1209: 070915-062123, 010715-062122, and 160614-046307); and Varley-Gradwell Travelling Fellowship

Two of the world’s most invasive ants, Linepithema humile and Lasius neglectus, are destined to overlap in range as they continue to spread throughout Europe. Although L. humile arrived first, and is therefore more numerically abundant, L. neglectus is the more behaviorally dominant of the two. We performed lab trials to determine whether L. humile could use numerical abundance to overcome the behavioral dominance of L. neglectus and whether the ants’ behavioral patterns shifted when the species co-occurred. We found that L. neglectus was more aggressive when less abundant, whereas the opposite was true of L. humile. When L. neglectus was outnumbered, it employed aggressive behaviors, such as biting or chemical attacks, more frequently than L. humile; it also utilized a behavioral sequence that included mandible opening and biting. Our results for these species support the hypothesis that species modulate their behavior towards competitors, which facilitates the understanding of how multiple invasive ant species can co-occur in a given area. Moreover, our study shows that the co-occurrence of invasive species could result from the use of two strategies: (1) the Bourgeois strategy, in which aggressiveness changes based on numerical dominance and (2) the dear-enemy strategy, in which aggressiveness is reduced when competitors co-occur. Since these strategies may lead to territory partitioning, we suggest that the behavioral flexibility displayed by both species when they overlap may allow local co-occurrence and increase their likelihood of co-occurrence during their range expansion in Europe, which could have a negative cumulative impact on invaded areas.

We report new localities for Callinectes sapidus in the Iberian Peninsula that widen the north-eastern limit of its distribution by more than 206 km along the Iberian Mediterranean coastline. This invasive species has been captured in the estuaries of the Fluvià, Muga and Ter rivers and has become established in the Fluvià River in only nine months since the first individual was detected. These reports show how rapid expansion of C. sapidus can be and that this may be preceded by the presence of isolated individuals We gratefully acknowledge the scientific team of the European Life project “Pletera” (LIFE13 NAT/ES/001001) and the Sorelló S.L. company for sharing their field results. This project has been financially supported by Natura Montfred company and the Aiguamolls de l’Empordà Natural Park (PNAE)

Mate recognition is the process of identifying and assessing the appropriate species, sex or population of another individual for their suitability as a potential mate. Recognition may be innate or learned. Learning, the acquisition of knowledge or skills through experience, involves a relatively long-term change in behavioral responses. In this study we examined learned and innate mate recognition in invasive male mosquitofish, Gambusia holbrooki, interacting with female conspecifics and male and female native toothcarp, Aphanius iberus. Male mosquitofish directed no mating attempts at male toothcarp whereas numerous attempts were made toward female toothcarp. Male mosquitofish therefore differentiated between males and females, but initially did not distinguish between con- and heterospecific females. Neither the presence of a male toothcarp, nor the presence of a refugia affected the number of mating attempts received by females. However, by the second day males appeared to learn to more accurately direct their mating attempts, with larger female mosquitofish receiving the most attention, though smaller toothcarp females were still harassed. We propose that male mosquitofish, with a coercive mating system, are selected for persistence despite rejection by potential mates. In this scenario, the pool of potential mates may include heterospecifics whose avoidance of mating attempts may be ignored by male mosquitofish. It may thus be adaptive for male mosquitofish to prioritize sex recognition over species recognition: if one sex is recognized as a “non-mate” this will cut 50% from the pool of potential mates whereas recognition of a single species will remove many fewer potential mates from the pool. This innate sex recognition together with rapid learning of species identity may be a factor in the invasive success of mosquitofish This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Program (KM). Additional financial support was provided by the Spanish Ministry of Science (projects CGL2009-12877-C02-01, CSD2009-00065, and PID2019-103936GB-C21).

Invasive alien species are one of the main components of global ecological change, the second known cause of animal extinctions, and very costly in terms of ecosystem services. Invasive alien species and damming are two of the most impacting alterations in freshwater ecosystems, and understanding the processes that govern biological invasions in these habitats is of enormous conceptual and practical importance. About 39 competing and overlapping hypotheses have been proposed in invasion biology that have been recently grouped in four (or five) concept clusters, namely the: propagule, resource availability, biotic interaction and Darwin’s clusters. We analyzed the relative importance of three of these concept clusters in Neotropical fish assemblages, using data from 29 reservoirs and variation partitioning analyses. We show that alien fish assemblages respond to variation in limnological characteristics in a way similar than native species, usually with positive effects of increased temperature, conductivity and chlorophyll-a concentration and decreasing turbidity. Overall, we found support for some hypotheses included in resource availability and Darwin’s clusters, such as increased resource availability and biotic acceptance, and no evidence of strong biotic resistance, marked effects of human disturbance, as measured by land-use changes, or propagule/colonization pressures. We discuss the potential reasons and management implications of these findings. Our study illustrates that analyzing the importance of classical hypotheses of invasion biology in tropical freshwaters and other ecosystems enhances ecological understanding and provides practical implications to prioritize management interventions and mitigate ecological impacts We express our appreciation to the PRONEX-MCT/CNPq for financial support and to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil, process number 88882.344464/2019-01) and to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brazil, process number 165319/2017-8) for the fellowships to graduate students. AAA received scientific productivity fellowships from CNPq. We are also grateful for the funding provided by CAPES through “Programa de Doutorado-sanduíche no Exterior” (PDSE, processes number 88881.361907/2019-01 and 88881.361938/2019-01) that allowed a research stay of CMM and MMG at the University of Girona. Additional financial support was provided by the Spanish Ministry of Science and Innovation (projects RED2018‐102571‐T and PID2019-103936GB-C21) and the Government of Catalonia (ref. 2017 SGR 548)

Invasive species pose a major threat to global diversity, and once they are well established their eradication typically becomes unfeasible. However, certain natural mechanisms can increase the resistance of native communities to invaders and can be used to guide effective management policies. Both competition and herbivory have been identified as potential biotic resistance mechanisms that can limit plant invasiveness, but it is still under debate to what extent they might be effective against well-established invaders. Surprisingly, whereas biotic mechanisms are known to interact strongly, most studies to date have examined single biotic mechanisms separately, which likely influences our understanding of the strength and effectiveness of biotic resistance against invaders. Here we use long-term field data, benthic assemblage sampling, and exclusion experiments to assess the effect of native assemblage complexity and herbivory on the invasion dynamics of a successful invasive species, the alga Caulerpa cylindracea. A higher complexity of the native algal assemblage limited C. cylindracea invasion, probably through competition by canopy-forming and erect algae. Additionally, high herbivory pressure by the fish Sarpa salpa reduced C. cylindracea abundance by more than four times. However, long-term data of the invasion reflects that biotic resistance strength can vary across the invasion process and it is only where high assemblage complexity is concomitant with high herbivory pressure, that the most significant limitation is observed (synergistic effect). Overall, the findings reported in this study highlight that neglecting the interactions between biotic mechanisms during invasive processes and restricting the studied time scales may lead to underestimations of the true capacity of native assemblages to develop resistance to invaders., Funding for this project was obtained from the Spanish Ministry Project ANIMA (CGL2016-76341-R, MINECO/FEDER, UE), the European Union’s EMFS Program, AFRIMED (EASME/EMFF/2017/1.2.1.12/S4/01/SI2.789059), the Spanish Autonomous Organism of National Parks through the project BIGPARK (project 2017-2462), and the Padi Foundation to FT (CGA App: 5134). JS received the support of a fellowship from “La Caixa” Foundation (ID 100010434) with code (LCF/BQ/DE17/11600001).

The extreme body sizes of megafishes associated with their high commercial values and recreational interests have made them highly threatened in their native range worldwide by human-induced impacts such as overexploitation. Meanwhile, some megafishes have been introduced outside of their native range. A notable example is the European catfish (Silurus glanis), one of the few siluriforms native to Eastern Europe. It is among the 20 largest freshwater fish worldwide, attaining a total length over 2.7 m and a documented mass of 130 kg. Its distinct phylogeny and extreme size imply many features that are rare among other European fish, including novel behaviours (massive aggregations, beaching), consumption of large bodied prey, fast growth rates, long lifespan, high fecundity, nest guarding and large egg sizes. The spread of the species is likely to continue due to illegal introductions, primarily for recreational angling, coupled with natural range extension associated with climate change. Here, the most recent knowledge on the current distribution and the ecology of the species are reviewed. A series of key research questions are identified that should stimulate new rese arch on this intriguing, yet largely unknown, species and, more generally, on the ecology of freshwater invaders This work was produced as part of the ‘‘European Catfish Working Group’’ that was financially supported by the University of Toulouse. Individual members of the group were supported by the Spanish Ministry of Economy and Competitiveness (Project CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), the European Commission (COST Action TD1209), Czech Science Foundation (Project 16-06498S) and the French Laboratory of Excellence Project ‘‘TULIP’’ (ANR-10-LABX-41; ANR-11-IDEX-0002-02)

Biological invasions rank among the main global threats for biodiversity. The Eastern mosquitofish (Gambusia holbrooki) is considered one of the 100 world worst invasive species due to its high adaptation capability to new environments. Using the restriction-site-associated DNA tags (RADtags), introduced European locations were compared against native US mosquitofish populations to analyse genomic changes that occurred during invasive process of European locations. After filtering, 7724 RADtags containing only one SNP were retained for population studies. Comparative genomics indicated that 186 of these RADtags matched sequences in the transcriptome of Xyphophorus maculatus, the most closely related genome available. Genomic analyses showed that invasive populations show high reductions in diversity. Further, analyses of population structuring based on these data are concordant with previous analyses based on microsatellites. It is concluded that during the invasion process genetic drift was the main evolutionary force affecting patterns of diversity and population structure. While recognizing that positive selection could be masked by the strong drift during founder events, adaptive processes were evidenced in a reduced number of RADtags (

This study provides the first detailed assessment of the vascular flora of the Cavallo Island and its three satellite islands or islets (Corsica, Bouchesde-Bonifacio). It is the Corsican island which has the highest floristic richness with 440 taxa (species and subspecies), all inventories combined. The current flora (i. e. occurring after 1990) includes 426 taxa, of which 371 indigenous and 55 exotic plants, introduced voluntarily or not by man. Of this total, 155 taxa (109 indigenous and 46 exotics) were never been reported on the Lavezzi archipelago. This high floristic richness, compared to other west-Mediterranean islands of similar size, is explained by the area of Cavallo island, the largest of the peri-corsican islands, and to the diversity of environments, including the presence of a permanent lake, the Greco lake. Cavallo Island and its islets contain 70 plant species of importance (i. e. endemic, rare, protected or threatened), eight of which were not currently inventoried. These surveys performed in 2013–2015 highlight the presence of some very rare plants in Corsica (Anacamptis morio subsp. longicornu, Callitriche brutia, Limonium bonifaciense, Limonium strictissimum) and infrequent endemics (Acis rosea, Bryonia marmorata, Crocus minimus, Serapias nurrica, Silene velutina) that were not known to the island. The strong human impact explains the presence of 55 introduced taxa and at least subspontaneous in the «natural environment», of which 50 had not yet been reported on the island. The results of this study are discussed in terms of (1) specific richness compared to other western Mediterranean islands of similar surface, (2) functional diversity (analysis of demographic strategies of Grime), (3) biogeographic originality and conservation issues in order to better preserve in the future this exceptional floristic heritage but for too long unrecognized., Cette étude dresse le premier bilan détaillé de la flore vasculaire de l’île Cavallo et de ses trois îles ou îlots annexes (Corse, Bouches-de-Bonifacio). Il s’agit de l’île satellite corse qui comporte la plus forte richesse floristique avec 440 taxons (espèces et sous-espèces) signalés, tous inventaires confondus. La flore actuelle (présence postérieure à 1990) s’élève à 426 taxons, dont 371 indigènes et 55 exotiques introduits volontairement ou non par l’homme. Parmi ce total, 155 taxons (109 indigènes et 46 exotiques) n’avaient jamais encore été signalés sur l’archipel des Lavezzi. Cette forte richesse floristique, comparée à celle d’autres îles ouest-méditerranéennes de taille voisine, est liée à la superficie de Cavallo, la plus vaste des îles péri-corses, et à la diversité des milieux dont la présence d’un plan d’eau permanent, l’étang du Greco. L’île Cavallo et ses îlots comportent 70 végétaux «patrimoniaux» (endémiques, rares, protégés ou menacés) dont 8 non revus actuellement. Les inventaires de 2013-2015 mettent notamment en évidence la présence de certains végétaux très rares en Corse (Anacamptis morio subsp., longicornu, Callitriche brutia, Limonium bonifaciense, Limonium strictissimum) et d’endémiques peu fréquents (Acis rosea, Bryonia marmorata, Crocus minimus, Serapias nurrica, Silene velutina) qui n’étaient pas connus de l’île. Les impacts anthropiques forts expliquent la présence de 55 taxons introduits et au moins subspontanés dans le «milieu naturel», dont 50 n’avaient pas été encore signalés sur l’île. Les résultats de cette étude sont discutés en terme (1) de richesse spécifique par rapport à des îles ouest-méditerranéennes de surfaces voisines, (2) de diversité fonctionnelle (analyse des stratégies démographiques de Grime), (3) d’originalité biogéographique et d’enjeux de conservation afin de mieux préserver à l’avenir ce patrimoine floristique exceptionnel mais resté trop longtemps méconnu., Médail Frédéric, Petit Yohan, Delage Alain, Paradis Guilhan, Hugot Laetitia. La flore vasculaire de l’île de Cavallo (archipel des Lavezzi, Corse) : diversité, intérêt biogéographique et conservation. In: Ecologia mediterranea, tome 43 n°2, 2017. Le patrimoine naturel de l'île de Cavallo (archipel des Lavezzi, Corse) : écologie, biogéographie et conservation. pp. 103-158.

Identificación y validación de PNU en dos especies invasoras: el mejillón cebra (Dreissena polymorpha) y la almeja asiática (Corbicula fluminea) El desarrollo de las plataformas asequibles de secuenciación masiva en paralelo (SMP) ha reducido el coste y el tiempo en la identificación de marcadores de polimorfismos de nucleótido único (PNU) para su uso en estudios de genética de poblaciones y de conservación. Tras la SMP, suele ser necesaria una segunda validación. El análisis de las curvas de fusión a alta resolución (HRMA en su sigla en inglés) es un método rápido y sencillo para escanear mutaciones y, por tanto, es un protocolo adecuado de validación de dichos marcadores, especialmente en especies no modelo. En este trabajo se presenta un juego de nueve marcadores polimórficos de PNU nuevos identificados mediante SMP y validados con el HRMA en dos especies invasoras (el mejillón cebra Dreissena polymorpha y la almeja asiática Corbicula fluminea), que pueden utilizarse en estudios de genética de poblaciones para evaluar y entender correctamente los episodios de invasión pasados y los que podrían ocurrir en el futuro., The development of affordable massive parallel sequencing (MPS) has reduced both time and costs of SNP identification for use in conservation and population genetic studies. After MPS, a second validation is usually required. High resolution melting analysis (HRMA) is a fast and simple method for mutation scanning, and thus a suitable validation protocol, particularly in non–model species. We present a set of nine novel polymorphic SNPs identified by MPS and validated with HRMA in two invasive species (the zebra mussel Dreissena polymorpha and the Asian clam Corbicula fluminea). These SNPs can be used in genetic studies to accurately assess and understand past and future invasion events.

Ecologists have recently devoted their attention to the study of species traits and their role in the establishment and spread of nonindigenous species (NIS). However, research efforts have mostly focused on studies of terrestrial taxa, with lesser attention being dedicated to aquatic species. Aquatic habitats comprise of interconnected waterways, as well as exclusive introduction vectors that allow unparalleled artificial transport of species and their propagules. Consequently, species traits that commonly facilitate biological invasions in terrestrial systems may not be as represented in aquatic environments. We provide a global meta-analysis of studies conducted in both marine and freshwater habitats. We selected studies that conducted experiments with native and NIS under common environmental conditions to allow detailed comparisons among species traits. In addition, we explored whether different factors such as species relatedness, functional feeding groups, latitude, climate, and experimental conditions could be linked to predictive traits. Our results show that species with traits that enhance consumption and growth have a substantially increased probability of establishing and spreading when entering novel ecosystems. Moreover, traits associated with predatory avoidance were more prevalent in NIS and therefore favour invasive species in aquatic habitats. When we analysed NIS interacting with taxonomically distinctive native taxa, we found that consumption and growth were particularly important traits. This suggests that particular attention should be paid to newly introduced species for which there are no close relatives in the local biota. Finally, we found a bias towards studies conducted in temperate regions, and thus, more studies in other climatic regions are needed. We conclude that studies aiming at predicting future range shifts should consider trophic traits of aquatic NIS as these traits are indicative of multiple interacting mechanisms involved in promoting species invasions This research was supported by the Spanish Ministry of Economy and Competitiveness (projects CGL2013-43822-R and CGL2015-69311-REDT), the Government of Catalonia (ref. 2014 SGR 484), and the European Commission (COST Action TD1209). P.S. work was supported by a doctoral fellowship from the European Commission (Erasmus Mundus Partnership ‘Techno’, 204323-1-2011-1-FREMA21)

In freshwater ecosystems, abiotic factors such as flow regime and water quality are considered important predictors of ecosystem invasibility. The aim of this study was to investigate the critical swimming capacity and metabolism of the eastern mosquitofish, Gambusia holbrooki, focusing on sex and size effects, to evaluate the influence of water flow on its invasive success. Specimens of mosquitofish were captured from the Ter Vell lagoon (L'Estartit, north-eastern Spain) in July 2014, and we measured the critical swimming speed (Ucrit) and oxygen consumption of individual fish (30 females and 30 males) using a mini swim tunnel. The mean Ucrit of this poeciliid fish was estimated at 14.11 cm·s-1 (range = 4.85-22.26), which is lower than that of many other fishes of similar size and confirms that this species is limnophilic and its invasive success might be partially explained by hydrologic alterations. However, the Ucrit and maximal metabolic rate vary markedly with fish size and sex, with males having much higher values for the same body mass, and thus probably being more resistant to strong water flows. Multiple regression models illustrate that multivariate analyses might increase the predictive power and understanding of swimming performance and metabolic traits, compared to results from conventional simple regressions This research was supported by the Spanish Ministry of Economy and Competitiveness (project CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), the European Commission (COST Action TD1209) and the Brazilian Ministry of Education (CAPES, ref. 88881.068352/2014-01). P.S. and Y.L. benefitted from fellowships from the European Commission (Erasmus Mundus Partnership ‘Techno’, 204323-1-2011-1-FR-EMA21)

Seed dispersal is a fundamental process in the lifecycle of all flowering plants. Many plant species have evolved specialist associations with biotic vectors to facilitate dispersal. Such specialised interactions mean that these associations are potentially highly sensitive to disruption, e.g. from invasive species. However, despite this threat we still understand remarkably little about how such perturbations affect the dynamics and efficiency of the seed-dispersal process. In this study we quantify the impacts of an invasive ant across three key phases of the seed dispersal process: seed removal, distribution and placement, in order to determine the stages of seed dispersal most vulnerable to disruption by invaders. Using the Argentine ant (Linepithema humile) as a model, we show that invaded sites exhibited a significant decrease in seed dispersal services across all three phases of the dispersal process, relative to non-invaded sites. Seeds dispersed in invaded sites were: (a) less likely to be transported; (b) potentially distributed over a smaller spatial area, and (c) less likely to be placed at soil depths favourable for germination and establishment compared to those dispersed in non-invaded sites. These results reveal that ant-mediated seed dispersal services are significantly reduced by an invasive species at multiple stages in the dispersal process. Reductions in the efficacy of seed dispersal, combined with shifts in the ecological and geographical patterns of dispersal, may lead to cascading impacts on plant species composition and community structure. This study shows how an invasive ant can affect seed dispersal at several stages in the dispersal process This work was funded by grants from the COST Action TD1209 (ECOSTSTSM-TD1209: 070915-062123, 010715-062122, and 160614-046307) and a National Environmental Research Council Case Studentship awarded to SS, JB and RN (NE/K007076/1)

Eastern Mosquitofish (Gambusia holbrooki) is an invasive and globally widespread species that is considered highly tolerant. We used species distribution models (SDMs) to assess factors, including the role of anthropogenic perturbation, that mediate its invasion on a regional scale. A better understanding of the important large-scale factors may help us identify future areas of concern and potential avenues for control. We built SDMs from presence records and randomly selected pseudo-absences of mosquitofish on a 10- × 10-km grid. We used 10 modeling techniques implemented in the biomod2 software and ensemble forecasts. Final models contained 12 environmental predictors, including natural environmental factors (elevation, slope, topographic index, precipitation, accumulated flow, temperature mean and range) and anthropogenic perturbation indicators (population density, urban and agricultural land uses, number of local and upstream dams). Elevation, temperature, and accumulated flow most strongly influenced mosquitofish distribution, and mosquitofish were found more frequently in downstream, warmer waters. Anthropogenic features, except the number of upstream dams, were poorer predictors of mosquitofish presence than were natural environmental factors. The best models suggested that mosquitofish are more likely to occur in areas with more dams upstream, but removing this predictor did not strongly affect model results. Restoration efforts or modifications to anthropogenic features appear unlikely to alter mosquitofish distribution patterns, highlighting the importance of preventing introductions to new areas. Mosquitofish have been extensively documented in the Iberian Peninsula, but consensus methods suggest many additional suitable areas from which records were not found. Thus, this highly invasive species is or may become much more widely distributed than current observations in the region Financial support was provided by the Spanish Ministry of Economy and Competitiveness (projects CGL2009-12877-C02-01, CSD2009-00065, and CGL2013-43822-R), the University of Girona (project SING12/09), and the Government of Catalonia (ref. 2014 SGR 484)

The temporal components of genetic diversity and geographical structure of invasive mosquitofish populations are poorly known. Through the genetic monitoring of four consecutive cohorts of Gambusia holbrooki from three different river basins we aimed to determine temporal patterns of regional genetic variation and dispersal rates within invasive populations. Despite showing evidence of strong population size fluctuations, genetic diversity levels were maintained among local cohorts. We only detected temporal allele frequency changes associated with seasonal flooding that did not modify major trends on population structure among cohorts. Downstream gene flow coupled with increased connectivity at lowland locations to increase genetic diversity levels in these areas. A large proportion of local fish (up to 50 %) were dispersers, often originated from locations within the same river basin. High dispersal capability, ecological tolerance, and reproductive traits likely promote river colonization. Finally, our results also confirmed that human-assisted translocations promote within and among basin gene flow and maintained levels of genetic diversity, particularly in upstream locations This work has been possible thank to the financial support of the former Spanish Ministry of Economy and Competitiveness (MINECO, CGL2009-12877-C02-02). DDM held a Ph.D. scholarship from the University of Girona (UdG, BR10/12)

Animal behaviour is of fundamental importance but is often overlooked in biological invasion research. A problem with such studies is that they may add pressure to already threatened species and subject vulnerable individuals to increased risk. One solution is to obtain the maximum possible information from the generated data using a variety of statistical techniques, instead of solely using simple versions of linear regression or generalized linear models as is customary. Here, we exemplify and compare the use of modern regression techniques which have very different conceptual backgrounds and aims (negative binomial models, zero-inflated regression, and expectile regression), and which have rarely been applied to behavioural data in biological invasion studies. We show that our data display overdispersion, which is frequent in ecological and behavioural data, and that conventional statistical methods such as Poisson generalized linear models are inadequate in this case. Expectile regression is similar to quantile regression and allows the estimation of functional relationships between variables for all portions of a probability distribution and is thus well suited for modelling boundaries in polygonal relationships or cases with heterogeneous variances which are frequent in behavioural data. We applied various statistical techniques to aggression in invasive mosquitofish, Gambusia holbrooki, and the concomitant vulnerability of native toothcarp, Aphanius iberus, in relation to individual size and sex. We found that medium sized male G. holbrooki carry out the majority of aggressive acts and that smaller and medium size A. iberus are most vulnerable. Of the regression techniques used, only negative binomial models and zero-inflated and expectile Poisson regressions revealed these relationships This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Programme (KM). Additional support was provided by the Spanish Ministry of Economy and Competitiveness (project CGL2013-43822-R), the University of Girona (project SING12/09), the Government of Catalonia (ref. 2014 SGR 484), and the European Commission (COST Action TD1209)

Polydomy associated with unicoloniality is a common trait of invasive species. In the invasive Argentine ant, colonies are seasonally polydomous. Most follow a seasonal fission-fussion pattern: they disperse in the spring and summer and aggregate in the fall and winter. However, a small proportion of colonies do not migrate; instead, they inhabit permanent nesting sites. These colonies are large and highly polydomous. The aim of this study was to (1) search for differences in the fecundity of queens between mother colonies (large and permanent) and satellite colonies (small and temporal), (2) determine if queens in mother and satellite colonies have different diets to clarify if colony size influences social organization and queen feeding, and (3) examine if colony location relative to the invasion front results in differences in the queen's diet. Our results indicate that queens from mother nests are more fertile than queens from satellite nests and that colony location does not affect queen oviposition rate. Ovarian dissections suggest that differences in ovarian morphology are not responsible for the higher queen oviposition rate in mother vs. satellite nests, since there were no differences in the number and length of ovarioles in queens from the two types of colonies. In contrast, the higher δ15N values of queens from mother nests imply that greater carnivorous source intake accounts for the higher oviposition rates This work was supported by the Ministry of Science and Innovation of the Government of Spain, and EU ERDF funds (CGL2010-16451)

The aquarium trade has been identified as an important vector of aquatic invasive species but this question has mostly been investigated in North America. We investigated the variation in diversity and species composition in different trade types in southwestern Europe (three major international wholesalers, different retail store types, and local internet forums), mostly in Spain and Portugal. As in previous studies, the diversity of fishes in the aquarium trade was vast, with a total of 20 orders, 79 families, and 1,133 fish species detected in the trade types analyzed. 248 species were observed in a single metropolitan area (Barcelona), with estimates of about 294 species being present. International wholesalers had higher species richness and evenness, with a single one having over 700 species. General pet stores had much lower evenness but due to high turnover had a total richness of over 200 species. Internet forums had the lowest evenness but similar richness. The different commerce types varied significantly in relative species abundance with about a dozen of popular fish species (e.g., goldfish, Siamese fighting fish, common carp, guppy, swordtails) dominating the retail stores, particularly the general pet stores. Our results imply that frequency in the trade varies strongly among species and commerce types and although general pet stores have usually low diversity, this is compensated with a higher species turnover. Many of the most popular species are well known invasive species and some of the species available are temperate species that might establish in Europe, reinforcing the need for more careful implementation of education programs, regulation and monitoring of trade, and internalization of environmental costs by the industry We thank the aquarium websites mentioned in the methods for the valuable information provided, the Spanish Ministry of Science for financial support (CGL2009-12877-C02-01 and Consolider-Ingenio 2010 CSD2009-00065), and Julian D. Olden, the associate editor, and anonymous reviewers for insightful comments on the manuscript

Because insectivorous birds must evaluate resources for reproduction before settling into a breed- ing habitat, they can fall into an ecological trap if informative cues about habitat suitability become dissociated from their actual yield. Given their potential to affect ecological networks, invasive ant species are potential candidates for triggering such ecological traps. We combined observational and experimental approaches to examine whether the variation in food supply for nestlings resulting from the invasion of the Argentine ant, Linepithema humile, had any influence on the breeding ecology of the blue tit, Cyanistes caeruleus, an insectivorous foliage-gleaner. We inves- tigated the effects of the ant invasion on breeding performance (nesting success, clutch size, brood size and breeding success) and offspring quality (body size and condition, developmental stability and plumage colour) in replicated Mediterranean forest areas over a period of 3 years. There was no evidence that the reduction in caterpillar availability resulting from the invasion had a concurrent negative effect on the blue tit’s ability to successfully rear nestlings in optimal conditions, at least as measured here. Although the raw figures suggest an increased level of nutritional stress in blue tits breeding in invaded forests, the data analyses showed no significant alterations in terms of productiv- ity or offspring fitness. The reproductive performance of the blue tit has been shown to be remarkably resilient to the Argentine ant-mediated food shortage, either because the prey reduction following the invasion did not reach a critical threshold or because of compensa- tory activity by the progenitors. We cannot conclusively reject an ecological trap triggered by the ant invasion on blue tits, since neither fledgling recruitment nor the prospective survival of parents were assessed. Even though we could not confirm short-term consequences of the Argentine ant invasion on blue tit reproductive fitness, the long-term bottom-up effects of the invasion remain unknown and should not be ruled out

The zebra mussel (Dreissena polymorpha Pallas, 1771) and the quagga mussel (D. rostriformis Deshayes, 1838) are successful invasive bivalves with substantial ecological and economic impacts in freshwater systems once they become established. Since their eradication is extremely difficult, their detection at an early stage is crucial to prevent spread. In this study, we optimized and validated a qPCR detection method based on the histone H2B gene to quantify combined infestation levels of zebra and quagga mussels in environmental DNA samples. Our results show specific dreissenid DNA present in filtered water samples for which microscopic diagnostic identification for larvae failed. Monitoring a large number of locations for invasive dreissenid species based on a highly specific environmental DNA qPCR assay may prove to be an essential tool for management and control plans focused on prevention of establishment of dreissenid mussels in new locations We are indebted to different colleagues for zebra mussel sample collections: Concha Durán (Ebro Hydrografic Confederation, Spain) for the logistic advice; Anna Terrats and Carolina Solà (Catalan Water Agency from the Government of Catalonia, Spain) for the filtered-water environmental samples. We would thank to Mariona Palacios for her collaboration in the analysis into her Final Master Project. This research was carried out within the objectives of the research project CGL200909407 of the Spanish Ministerio de Ciencia e Innovación (MICINN)

Habitat degradation has a major impact on freshwater ecosystems and also facilitates biological invasions thus intensifying the problem. The survival of native species under threat from invaders can be improved either by eradicating the invading species or by providing resources or conditions that benefit the native species. One such resource is shelter and in degraded habitats artificial refugia may be a viable option. However, the use of artificial refugia to promote coexistence between native and invasive species remains poorly understood. We assessed the potential for artificial refugia to ameliorate the disruption of social interactions in an endangered native Iberian toothcarp, Aphanius iberius, by the invasive mosquitofish, Gambusia holbrooki. We found that mosquitofish do not compete for access to refugia despite their higher level of aggression compared to native fish. Native fish use refugia more overall, particularly in the presence of mosquitofish. Despite this, the benefits of refugia are not clear cut: increases in refuge use by male toothcarp induced by mosquitofish aggression correspond to decreases in attention to conspecifics. However, changes in refugia use over time together with constant attention to conspecifics indicates that it is not refugia use itself that disrupts social interactions but the interrelated effects of mosquitofish aggression. Provision of artificial refugia in degraded freshwater ecosystems may thus be a viable management tool to protect native populations under imminent threat of invasion This research was supported by a Marie Curie International Reintegration Grant within the 7th European Community Framework Programme (KM). Additional support was provided by the SpanishMinistry of Economy and Competitiveness (projects CGL2009-12877-C02-01 and CGL2013-43822-R), the Government of Catalonia (ref. 2014 SGR 484), and the European Commission (COSTAction TD1209)

Because invasive species threaten the integrity of natural ecosystems, a major goal in ecology is to develop predictive models to determine which species may become widespread and where they may invade. Indeed, considerable progress has been made in understanding the factors that influence the local pattern of spread for specific invaders and the factors that are correlated with the number of introduced species that have become established in a given region. However, few studies have examined the relative importance of multiple drivers of invasion success for widespread species at global scales. Here, we use a dataset of >5,000 presence/absence records to examine the interplay between climatic suitability, biotic resistance by native taxa, human-aided dispersal, and human modification of habitats, in shaping the distribution of one of the world's most notorious invasive species, the Argentine ant (Linepithema humile). Climatic suitability and the extent of human modification of habitats are primarily responsible for the distribution of this global invader. However, we also found some evidence for biotic resistance by native communities. Somewhat surprisingly, and despite the often cited importance of propagule pressure as a crucial driver of invasions, metrics of the magnitude of international traded commodities among countries were not related to global distribution patterns. Together, our analyses on the global-scale distribution of this invasive species provide strong evidence for the interplay of biotic and abiotic determinants of spread and also highlight the challenges of limiting the spread and subsequent impact of highly invasive species We acknowledge financial support from the Centre of Excellence for Invasion Biology (N.R.-P. and D.M.R.), from the Catalan Agency for Management of University and Research Grants (Generalitat de Catalunya) through Beatriu de Pinós Postdoctoral Grants 2006 BP-A 10124 and 2008 BP-B 00042 (to N.R.-P.), from the Hans Sigrist Foundation (to D.M.R.), from the Spanish Ministry of Science and Innovation Grant CGL2007-64080-C02-02/BOS (to C.G. and N.R.-P.), from the Spanish Ministry of Science and Innovation and the European Regional Development Fund Grant CGL2007-64080-C02-01/BOS (to X.E.), from the Blue Skies Programme of the National Research Foundation (to C.H.), from the Danish National Research Foundation (to J.S.P.), from Department of Energy–Program for Ecosystem Research Grant DE-FG02-08ER64510 (to N. J.S.), from National Science Foundation Grant DEB 0716966 (to A.V.S.), and from the New Zealand Foundation for Research, Science, and Technology Grant C09X0507 (to D.W.)

The increasing numbers of invasive species have stimulated the study of the underlying causes promoting the establishment and spread of exotic species. We tracked the spread of the highly invasive Argentine ant (Linepithema humile) along an environmental and habitat gradient on the northeastern Iberian Peninsula to determine the role of climatic, habitat and biotic variables on the rate of spread, and examine impact on native ant communities. We found the species well-established within natural environments. The mean annual rate of spread of the invasion (7.94 ± 2.99 m/year) was relatively low compared to other studies, suggesting that resistance posed by native ants in natural environments with no or low human disturbance might delay (although not prevent) the spread of the invasion irrespectively of the land-use type. Factors related to the distance to urban areas and characteristics of native and introduced populations explained the rate of spread of the invasion, while habitat-related variables determined the distribution of native ants and the impact of the Argentine ant on them. Native ant communities became more homogeneous following the invasion due to the decline of species richness and abundance. Only few species (Plagiolepis pygmaea and Temnothorax spp.) were able to cope with the spread of the invasion, and were possibly favored by the local extinction of other ant species. Taken together, our results indicate that land uses per se do not directly affect the spread of L. humile, but influence its invasive success by molding the configuration of native ant communities and the abiotic suitability of the site Financial support for this study came from Beatriu de Pino´s Postdoctoral Grant (2006 BP-A 10124) from the Catalan Agency for Management of University and Research Grants (in support of NRP), the Ministry of Education and Science of the Spanish Government CGL2004-05240-C02-02/BOS (NRP and JMB)

Determining the geographical range of invasive species is an important component of formulating effective management strategies. In the absence of detailed distributional data, species distribution models can provide estimates of an invasion range and increase our understanding of the ecological processes acting at various spatial scales. We used two complementary approaches to evaluate the influence of historical and environmental factors in shaping the distribution of the Argentine ant (Linepithema humile), a widespread, highly invasive species native to South America. Occurrence data were combined with environmental data at incremental spatial scales (extent and resolution) to predict the suitable range of the ant invasion using ecological niche models. In addition, we also used a spread model that simulated the jump dispersal of the species to identify the most plausible scenarios of arrival of L. humile in the NE Iberian Peninsula at local scales. Based on the results of both modelling practices, we suggest that L. humile might have reached its maximum geographic range at regional scales in the NE Iberian Peninsula. However, the species does not appear in equilibrium with the environment at small spatial scales, and further expansions are expected along coastal and inland localities of the Costa Brava. Long-distance jumps are ultimately responsible for the spread of the Argentine ant in the area. Overall, our study shows the utility of combining niche based models with spread models to understand the dynamics of species' invasions Financial support for this study came from Beatriu de Pino´s postdoctoral grant (2006 BP-A 10124) from Catalan Agency for Management of University and Research Grants (in support of NRP), the Ministry of Education and Science of the Spanish Government CGL2004-05240-C02-02/BOS (NRP and JMB).

We provide mitochondrial sequence variation of the invasive fish Gambusiaholbrooki from 24 European populations, from Portugal to Greece. Phylogeographic structure in Europe was compared with genetic data from native samples (USA) and historical records were reviewed to identify introduction routes. Overall, data agree with records of historical introductions and translocations, and indicate that the most abundant haplotype throughout Europe originated from North Carolina and corresponded to the first introduction in 1921 to Spain, being transferred to Italy in 1922 and to many countries afterwards. Our results also show that at least another independent introduction occurred first in France and subsequently from France to Greece. Haplotypes of G. affinis were not detected in our European sampling effort but historical records and other data suggest that this species was introduced to Italy in 1927 and it might be present. At the continental scale, there is less diversity in Europe than in North America, in agreement with the low number of introduced fish. At the local scale, some European populations gained diversity from multiple introductions and from "de novo" mutations This study was financially supported by the Spanish Ministry of Education (CGL2006-11652-C02-02/BOS) and the Government of Catalonia (Catalan Government Distinction Award for University Research 2004 to EGB)

8 páginas, 6 figuras, In the current global climate change scenario, stressors overlap in space and time, and knowledge on the effects of their interaction is highly needed to understand and predict the response and resilience of organisms. Corals, among many other benthic organisms, are affected by an increasing number of global change-related stressors including warming and invasive species. In this study, the cumulative effects between warming and invasive algae were experimentally assessed on the temperate reefbuilder coral Cladocora caespitosa. We first investigated the potential local adaptation to thermal stress in two distant populations subjected to contrasting thermal and necrosis histories. No significant differences were found between populations. Colonies from both populations suffered no necrosis after long-term exposure to temperatures up to 29°C. Second, we tested the effects of the interaction of both warming and the presence of invasive algae. The combined exposure triggered critical synergistic effects on photosynthetic efficiency and tissue necrosis. At the end of the experiment, over 90% of the colonies subjected to warming and invasive algae showed signs of necrosis. The results are of particular concern when considering the predicted increase of extreme climatic events and the spread of invasive species in the Mediterranean and other seas in the future., We thank the Secretaría General de Pesca (MAGRAMA) and the Columbretes Islands Marine Reserve staff for their logistic support. Support for this work was provided by a Ramon y Cajal research contract (RyC- 2011-08134) to C.L. and by a JAE-doc (FSE) to E.C. This study was funded by the Spanish Ministry of Economy and Innovation Smart project (CGL2012-32194).

How trophic resources are managed is a key factor in our understanding of the success of invasive species. In amphibians that usually occupy ephemeral ponds, the capacity to acquire resources and food selection are especially important because as a pond dries, the larval density increases and food resources are limited. Abundant and high-quality food can increase the final size and reduce the duration of development of amphibians. The aim of this work was to assess the trophic traits of tadpoles of the invasive (originally North African) anuran Discoglossus pictus compared to those of native European Epidalea calamita tadpoles under laboratory conditions. Food of two different levels of quality was supplied, and the feeding activity and food preference of the two species were analysed alone and in co-occurrence. D. pictus was capable of modifying its behaviour and food preferences; while E. calamita displayed much milder differences between treatments. Both alone and in co-occurrence with the native species, the invasive tadpoles obtained higher feeding activity values and showed a stronger preference for high-quality food. Additionally, when high densities of the two species shared food resources, the feeding activity results indicated potential displacement of the native tadpoles to low-quality resources. D. pictus thus presents trophic traits that are favourable for invasion and could limit the fitness of E. calamita when resources are limited or there is a risk of pond desiccation.

The dynamic in Argentine ant colonies varies seasonally, influenced by biotic and abiotic factors. In winter the spatial range of the colony is contracted in large formations (winter nests) containing a large number of queens and workers. Winter nests are the clue to the species' dispersion power and the invasion of new habitats. For this reason a yearly elimination of queens and workers in winter at the edge (front) of the invasion could be a useful tool for weakening the species' dispersion and therefore limiting its establishment in new areas. Here, we determined the spatial dynamics of the Argentine ant nests during 1 year, and we assessed the invasion management by means of manual removal of winter nests for two consecutive winters, determining its effects during the following 3 years. We mapped nests found in 18 plots divided into two groups: extirpated (with removal of nests) and non-extirpated (control), along the fronts of three locations. Seasonal variation in the abundance of nests and workers, together with the two-year extirpation effects were evaluated. We found that colonies tended to follow an annual cycle of contraction and dispersion, with a decrease in the number of nests as we approached the invasion front. The extirpation was effective only in the front area, where it promoted smaller, less lasting and aggregated nests, as well as a decrease in the abundance of queens and workers. Nests also experienced a decrease during the two first winters but a recovery in the third, when no extirpation was done. Thus, a yearly perturbation should be performed to keep the expansion of the Argentine ant at a low rate, and to limit its establishment in new areas This work was financed by the Spanish Ministry of Science and Innovation with the support of a predoctoral grant (BES-2008-005102) associated with research projects MEC/FEDER2007-64080-C02-02/BOS and CGL2010-16451, and a FI grant from the European Social Fund and the DIUE of the Autonomous Government of Catalonia in support of MLE

Genetic analyses contribute to studies of biological invasions by mapping the origin and dispersal patterns of invasive species occupying new territories. Using microsatellite loci, we assessed the genetic diversity and spatial population structure of mosquitofish (Gambusia holbrooki) that had invaded Spanish watersheds, along with the American locations close to the suspected potential source populations. Mosquitofish populations from the Spanish streams that were studied had similar levels of genetic diversity to the American samples; therefore, these populations did not appear to have undergone substantial losses of genetic diversity during the invasion process. Population structure analyses indicated that the Spanish populations fell into four main clusters, which were primarily associated with hydrography. Dispersal patterns indicated that local populations were highly connected upstream and downstream through active dispersal, with an average of 21.5% fish from other locations in each population. After initially introducing fish to one location in a given basin, such dispersal potential might contribute to the spread and colonization of suitable habitats throughout the entire river basin. The two-dimension isolation-by-distance pattern here obtained, indicated that the human-mediated translocation of mosquitofish among the three study basins is a regular occurrence. Overall, both phenomena, high natural dispersal and human translocation, favor gene flow among river basins and the retention of high genetic diversity, which might help retain the invasive potential of mosquitofish populations.

Biological invasions are considered one of the main anthropogenic factors that reduce the abundance of native species. Understanding the patterns of population structure and behavior of introduced species is important to determine invasion sources and pathways, in addition to improving the protective management of native species. Thus, we set out to advance our knowledge about the mosquitofish Gambusia spp., which is an invasive species that was introduced to southern Europe in 1921 to control mosquito populations. We assessed the genetic diversity and population structure of this species at 13 European locations, by screening variation at six microsatellite loci. We also evaluated six American samples (four of G. holbrooki and two of G. affinis) to identify the most likely source of the populations that established in Europe, and to determine whether G. affinis is also present. The results showed that, while there was evidence of recent bottleneck events in a few isolated locations, most introduced populations harbored a considerable amount of gene diversity, probably because of multiple introductions and secondary contacts. Populations displayed strong genetic differentiation that was mainly associated with geographical distance. At least two main routes of colonization of G. holbrooki seem to have occurred in Europe. The first, and more ancient colonization, was consistent with historical records, with the species invading the Iberian Peninsula. A second and more recent colonization probably occurred in Greece and, from there, France. The presence of G. affinis was not detected in any of the European samples The work was funded by the Spanish Ministry of Education and Science (MEC) research projects CGL2006-11652-C02-02/BOS and CGL2009-12877-C02-02

Study of the impacts of biological invasions, a pervasive component of global change, has generated remarkable understanding of the mechanisms and consequences of the spread of introduced populations. The growing field of invasion science, poised at a crossroads where ecology, social sciences, resource management, and public perception meet, is increasingly exposed to critical scrutiny from several perspectives. Although the rate of biological invasions, elucidation of their consequences, and knowledge about mitigation are growing rapidly, the very need for invasion science is disputed. Here, we highlight recent progress in understanding invasion impacts and management, and discuss the challenges that the discipline faces in its science and interactions with society., The workshop that spawned this paper was sponsored by CEFE-CNRS, the University of Montpellier (UM2) and the Région Languedoc Roussillon. P.P. was supported by grant no. P504/11/1028 (Czech Science Foundation), long-term research development project no. RVO 67985939 (Academy of Sciences of the Czech Republic), institutional resources of Ministry of Education, Youth and Sports of the Czech Republic, and acknowledges the support by Praemium Academiae award from the Academy of Sciences of the Czech Republic. D.A.W. was supported by a Wallenberg Scholars award, E.G.B. by the Spanish Ministry of Science (projects CGL2009-12877-C02-01 and CSD2009- 00065), M.V. by the Spanish Ministry of Science projects CGL2009-7515 and CSD2008-00040 and the Junta de Andalucıía RNM-4031, and F.C. by the French ANR (2009 PEXT 010 01)., info:eu-repo/semantics/publishedVersion

Contact: gauthier.dobigny@ird.fr; International audience; Invading rodent species can harbor parasites with potential transmission to native rodents and/or humans. To investigate trypanosomes prevalence in rodents, the spleen of 76 rodents from Niger identified by their karyotype was used as a DNA source for Trypanosoma detection using a newly developed qPCR assay. Of the invasive black rat, Rattus rattus, 71% (10/14) were PCR positive as well as 6% (4/62) of native African rodents. Sequences of 400 bp of the SSU rDNA gene identified phylogenetically close Trypanosoma lineages. Trypanosoma lewisi was present in all positive black rats and the sequences displayed 100% similarity with T. lewisi-infected humans in Senegal. T. lewisi was also detected in one Acomys johannis, suggesting a possible transmission to native species. In addition to improved knowledge of Trypanosoma diversity in rodents, our data underscore the introduction of the potentially pathogenic T. lewisi kinetoplastid through the human-mediated invasion of black rats all over West Africa

The influence of temperature on the developmental times and survival of insects can largely determine their distribution. For invasive species, like the Argentine ant, Linepithema humile Mayr (Hymenoptera: Formicidae), these data are essential for predicting their potential range based on mechanistic models. In the case of this species, such data are too scarce and incomplete to make accurate predictions based on its physiological needs. This research provides comprehensive new data about brood survival and developmental times at a wide range of temperatures under laboratory conditions. Temperature affected both the complete brood development from egg to adult worker and each of the immature stages separately. The higher the temperature, the shorter the development times. Brood survival from egg to adult was low, with the maximum survival rate being only 16% at 26 degrees C. Temperature also affected survival of each of the immature stages differently: eggs were negatively affected by high temperatures, while larvae were negatively affected by low temperatures, and the survival of pupae was apparently independent of environmental temperature. At 32 degrees C no eggs survived, while at 18 degrees C less than 2% of the eggs hatched into larva. The data from the present study are essential for developing prediction models about the distribution range of this tramp species based on its physiological needs in relation to temperature.

Alien species invading freshwater systems are causing major changes in biodiversity worldwide. Some alien species have been used as indicators of water quality and environmental degradation. We discuss the reasons for monitoring invasive species beyond their use as ecological indicators, and offer guidance on the design of appropriate long-term monitoring schemes. Monitoring plays an essential role in providing an early warning system, because eradication of alien species at the early stages of invasion is more effective and less costly than when the invader is established. Monitoring the presence of aliens is also more effective when associated to monitoring the vectors known to transport them, and is equally valuable after eradication and to determine the effects management and whether restoration has been achieved. Scientifically, monitoring an invasion in conjunction with measuring other abiotic and biotic parameters provides baseline information on the dynamics of the invasion, the vulnerability of the habitat to invasion and on the impacts of the invader. Combining information on the patterns of invasion with that of the regional environmental factors operational at the time is relevant to establishing relationships between the invasion and other global change components. Overall, the long-term monitoring of biological invasions, that integrates information before, during and after an invasion provides valuable information for both managers and scientists

The eastern mosquitofish (Gambusia holbrooki) is among the most invasive fish worldwide and yet, while very abundant in most Mediterranean countries, it is unable to tolerate the colder winters of northern and central Europe. Understanding the effects of latitude on its life-history traits is essential to predict the potential for its invasion of central Europe in current scenarios of climate change. We studied the variation of life-history traits and parasite load in the eastern mosquitofish along a latitudinal gradient from southern France to southern Spain, sampling mosquitofish populations in eight Mediterranean river mouths ranging 5° in latitude. Southern mosquitofish populations displayed higher catch rates, allocated more energy to reproduction (gonadosomatic index and gonadal weight after accounting for fish size) and had a lower condition (total weight and eviscerated weight after accounting for fish size) than in northern populations. Despite variability among populations, size-at-maturity (L50) significantly varied with latitude and northern individuals matured at smaller size (lower L50). Parasite prevalence ranged from 0.0 to 26.7% but parasite richness was very low; all the parasites identified were larvae of pleurocercoid cestodes belonging to the order Pseudophyllidea. The abundance of mosquitofish parasites decreased with latitude and the presence and number of parasites infecting the mosquitofish had a significant negative effect on fish condition. The significant effects of latitude on the catch rates, life history and parasites of mosquitofish highlight the importance of latitudinal studies of invasive species to understand the interactive mechanisms of climate change and biological invasions This study was financially supported by the Government of Catalonia (AIRE 2003 and Catalan Government Distinction Award for university research 2004 to EGB) and the Spanish Ministry of Education (REN2003-00477 and CGL2006-11652-C02-01/BOS)

To address the lack of physiological approaches in current models assessing the potential distribution of the Argentine ant, we used data on brood development from distinct sources to evaluate a series of degree-day models for Catalonia (NE Iberian Peninsula), and data on the brood survival and oviposition rates to develop a worker production model. The degree-day model generated using data from Newell and Barber (1913) and Benois (1973) indicated that the number of degree-days required for the complete development from egg to adult worker was 445.4 degree-days above a threshold of 15.9 °C, while the model calibrated using data from Abril et al. (2008, in press) suggested 599.5 degree-days above 18.4 °C. Comparisons between the degree-day model predictions and the currently known distribution of the Argentine ant suggested that the one generated using data from Newell and Barber (1913) and Benois (1973) overestimated the presence of the species, while the one calibrated using data from Abril et al. (2008; in press) underestimated it. On the other hand, the predicted daily net production of Argentine ant workers generated by the worker production model predicted more accurately the distribution of the Argentine ant than the degree-day models. Our results show the utility of incorporating physiological data in models to assess the distribution limits of the Argentine ant, which up to date have taken little account of the physiological needs of the species in terms of its establishment and dispersion in its introduced ranges This study was financed by the Spanish Ministry of Education and Science (CGL2004-05240-C02-02/BOS and MEC/FEDER2007-64080-C02-02/BOS). S. Abril acknowledges support from the University of Girona, and N. Roura-Pascual from the Catalan Agency for Management of University and Research Grants (Generalitat de Catalunya) through a Beatriu de Pino´ s Postdoctoral Grant (2006 BPA 10124)

The mosquitofish (Gambusia holbrooki) is among the most invasive fish worldwide, with well documented ecological impacts on ecosystem functioning and several native taxa. Although it has been suggested that salinity limits the invasive success of mosquitofish, there are few studies on how salinity affects its ecology. We examined differences in life history traits of mosquitofish at 19 sampling sites from fresh (438 μS/cm; ca. 0.2‰ of salinity) to polysaline waters (35.1 mS/cm; ca. 23‰). Salinity affected the density and life history traits of both male and female mosquitofish; density showed a unimodal response to salinity, stronger for females and thus affecting the sex ratio. On the other hand, the endemic Aphanius iberus was only present in polysaline and eusaline waters, where mosquitofish were generally absent. Mosquitofish increased reproductive investment (higher gonadal mass) in oligosaline waters, at the cost of somatic condition in females. The increase in reproductive investment also implied an increase in total mass in contrast to somatic mass, demonstrating that the latter is a better indicator of condition. Females from higher salinity waters presented more embryos in advanced developmental stages, indicating earlier reproduction than in fresh water. After correction for brood and fish sizes, females from saltier environments presented heavier embryos (independently of maturation state). In summary, salinity mainly affected mosquitofish females which, despite presenting earlier maturation and higher reproductive investment, reduced their condition and density, hence supporting the hypothesis that salinity limits mosquitofish invasive success Financial support was provided by the Spanish Ministry of Science and Technology (REN2003-00477) and the Government of Catalonia (Catalan Government Distinction Award for university research 2004 to EGB)

The zebra mussel (Dreissena polymorpha, Pallas, 1771) is one of the most invasive species of freshwater bivalves, due to a combination of biological and anthropogenic factors. Once this species has been introduced to a new area, individuals form dense aggregations that are very difficult to remove, leading to many adverse socioeconomic and ecological consequences. In this study, we identified, tested, and validated a new set of polymorphic microsatellite loci (also known as SSRs, Single Sequence Repeats) using a Massive Parallel Sequencing (MPS) platform. After several pruning steps, 93 SSRs could potentially be amplified. Out of these SSRs, 14 were polymorphic, producing a polymorphic yield of 15.05%. These 14 polymorphic microsatellites were fully validated in a first approximation of the genetic population structure of D. polymorpha in the Iberian Peninsula. Based on this polymorphic yield, we propose a criterion for establishing the number of SSRs that require validation in similar species, depending on the final use of the markers. These results could be used to optimize MPS approaches in the development of microsatellites as genetic markers, which would reduce the cost of this process

The interplay of abiotic factors and competition has a long history in ecology, although there are very few studies on the interaction of salinity and competition in fish. Mosquitofish (Gambusia holbrooki) are among the most invasive fish worldwide, with well documented ecological impacts on several taxa such as amphibians and small native fish. It has been previously hypothesized, based on field observations, that salinity limits the invasive success of mosquitofish and provides a competitive refuge for Mediterranean cyprinodonts. We experimentally tested this hypothesis by examining the agonistic behaviour and food competition between mosquitofish and an endangered native cyprinodont (Aphanius fasciatus) at three salinities (0, 15, 25‰). Intraspecific aggressive behaviour for both species was not significantly affected by salinity. As salinity increased, mosquitofish decreased their aggressive behaviour towards cyprinodonts and captured less prey. In contrast, the cyprinodonts did not change their behaviour with different salinity treatments, with the possible exception of increased defensive acts in higher salinities, but captured more prey with increasing salinity because of the reduced efficiency of mosquitofish. Our study confirms previous field observations that salinity limits the invasive success of mosquitofish and provides one of the few experimental demonstrations that it may mediate behavioural and competitive interactions between fish species. Condition-specific competition of mosquitofish might be expected with other species and ecosystems worldwide and illustrates the importance of integrating biotic and abiotic factors in the study of interspecific interactions Financial support was provided by the Spanish Ministry of Education (REN2003-00477) and the Government of Catalonia (Catalan Government Distinction Award for university research 2004)

Aquest article va ser corregit l'1 de juliol de 2014. La correcció es va publicar a Biology Letters, 2014, vol. 10, núm. 7, p. 20140504 Human transportation facilitates the dispersal of exotic ants, but few studies have quantified the magnitude and geography of these movements. We used several non-parametric indices to estimate the number of species successfully introduced to or established in new regions. We also compared their source biogeographic realms to assess the importance of geographical origin in determining the likelihood of establishment after introduction. Occurrence data on exotic ants derive from studies of three temperate regions. Our results suggest that the numbers of introduced or established ants may be much larger than the numbers so far documented. Ants introduced or established in new regions tend to arrive from the same or neighbouring realms, as would be expected if exotic species tend to match climates and if arrival/establishment is dependent upon higher trade rates from neighbouring countries V.M. and C.G. received support from MICINN (CGL2010-16451), N.R-P. from MICINN (CSD2008-00040) and R.R.D. from US DOE PER (DE-FG02-08ER64510), NASA Biodiversity (ROSES-NNX09AK22G) and NSF Career (0953390) grants

Charles Elton was a founder of ecology with fundamental contributions to diverse topics such as fluctuations of animal populations, food web theory, or what is now known as the Eltonian definition of the ecological niche (Macfadyen 1992; Simberloff 2000; Hardy 2002). His 1927 book Animal Ecology was reprinted many times and he was the first editor of the Journal of Animal Ecology. One of Elton’s most influential contributions, however, was his book The ecology of invasions by animals and plants, first published in 1958. Although many earlier authors including Darwin had dealt with invasive species, this book has been considered the starting point for focused scientific attention on biological invasions and is the most cited reference in the field (Pysek et al. 2006; Richardson and Pysek 2007; Ricciardi and MacIsaac 2008; Richardson and Pysˇek 2008) I thank the Editor-in-Chief, D. Simberloff, for helpful comments and the Spanish Ministry of Education for financial support (CGL2006-11652-C02/BOS)