The Plasticene era: Current uncertainties in estimates of the hazards posed by tiny plastic particles on soils and terrestrial invertebrates.

Plastics are ubiquitous in our daily life. Large quantities of plastics leak in the environment where they weather and fragment into micro- and nanoparticles. This potentially releases additives, but rarely leads to a complete mineralization, thus constitutes an environmental hazard. Plastic pollution in agricultural soils currently represents a major challenge: quantitative data of nanoplastics in soils as well as their effects on biodiversity and ecosystem functions need more attention. Plastic accumulation interferes with soil functions, including water dynamics, aeration, microbial activities, and nutrient cycling processes, thus impairing agricultural crop yield. Plastic debris directly affects living organisms but also acts as contaminant vectors in the soils, increasing the effects and the threats on biodiversity. Finally, the effects of plastics on terrestrial invertebrates, representing major taxa in abundance and diversity in the soil compartment, need urgently more investigation from the infra-individual to the ecosystem scales.

Taming the terminological tempest in invasion science.

Standardised terminology in science is important for clarity of interpretation and communication. In invasion science - a dynamic and rapidly evolving discipline - the proliferation of technical terminology has lacked a standardised framework for its development. The result is a convoluted and inconsistent usage of terminology, with various discrepancies in descriptions of damage and interventions. A standardised framework is therefore needed for a clear, universally applicable, and consistent terminology to promote more effective communication across researchers, stakeholders, and policymakers. Inconsistencies in terminology stem from the exponential increase in scientific publications on the patterns and processes of biological invasions authored by experts from various disciplines and countries since the 1990s, as well as publications by legislators and policymakers focusing on practical applications, regulations, and management of resources. Aligning and standardising terminology across stakeholders remains a challenge in invasion science. Here, we review and evaluate the multiple terms used in invasion science (e.g. 'non-native', 'alien', 'invasive' or 'invader', 'exotic', 'non-indigenous', 'naturalised', 'pest') to propose a more simplified and standardised terminology. The streamlined framework we propose and translate into 28 other languages is based on the terms (i) 'non-native', denoting species transported beyond their natural biogeographic range, (ii) 'established non-native', i.e. those non-native species that have established self-sustaining populations in their new location(s) in the wild, and (iii) 'invasive non-native' - populations of established non-native species that have recently spread or are spreading rapidly in their invaded range actively or passively with or without human mediation. We also highlight the importance of conceptualising 'spread' for classifying invasiveness and 'impact' for management. Finally, we propose a protocol for classifying populations based on (i) dispersal mechanism, (ii) species origin, (iii) population status, and (iv) impact. Collectively and without introducing new terminology, the framework that we present aims to facilitate effective communication and collaboration in invasion science and management of non-native species.

Assessing the potential phytosanitary threat of the house cricket Acheta domesticus.

Phytosanitary threats can pose substantial risks to global agriculture and ecological systems, affecting biodiversity, human well-being, and food security. Meanwhile, global warming is projected to exacerbate these threats in the future. One in Europe already widely distributed potential phytosanitary threat that may benefit from global warming is the house cricket Acheta domesticus. This study explored the potential of A. domesticus as a relevant non-native phytosanitary threat under changing climatic conditions by conducting a series of functional response experiments across a temperature gradient (20, 25, and 30 °C). Acheta domesticus exhibited comparable patterns of seed consumption and functional responses. Seed type (millet seeds, wheat grains) and temperature increase influenced the damage inflicted on seeds, with softer and smaller seeds being more susceptible to damage, further amplified by warmer temperatures. The study's outcomes underline the phytosanitary threat that A. domesticus may pose. Considering the species' established presence and adaptable nature in urban environments exacerbates the potential for A. domesticus to transition to rural and agricultural areas. Its increasing production as a food item, paired with the here-identified potential to damage seeds, emphasizes the need for proactive and science-based strategies to address emerging phytosanitary threats driven by non-native species under changing climatic conditions. As global temperatures continue to rise, the assessment and management of potential pest species like A. domesticus will be crucial for safeguarding agriculture productivity and ecological balance.

The wild cost of invasive feral animals worldwide.

Invasive non-native species are a growing burden to economies worldwide. While domesticated animals (i.e. livestock, beasts of burden or pets) have enabled our ways of life and provide sustenance for countless individuals, they may cause substantial impacts when they escape or are released (i.e. become feral) and then become invasive with impacts. We used the InvaCost database to evaluate monetary impacts from species in the Domestic Animal Diversity Information System database. We found a total cost of $141.95 billion from only 18 invasive feral species. Invasive feral livestock incurred the highest costs at $90.03 billion, with pets contributing $50.93 billion and beasts of burden having much lower costs at $0.98 billion. Agriculture was the most affected sector at $80.79 billion, followed by the Environment ($43.44 billion), and Authorities-Stakeholders sectors ($5.52 billion). Damage costs comprised the majority ($124.94 billion), with management and mixed damage-management costs making up the rest ($9.62 and $7.38 billion, respectively). These economic impacts were observed globally, where Oceania, North America and Europe were the most impacted regions. Islands recorded a higher economic burden than continental areas, with livestock species dominating costs more on islands than mainlands compared to other feral species. The costs of invasive feral animals were on average twice higher than those of wild species. The management of invasive feral populations requires higher investment, updated regulations, and comprehensive risk assessments. These are especially complex when considering the potential conflicts arising from interventions with species that have close ties to humans. Effective communication to raise public awareness of the impacts of feral populations and appropriate legislation to prevent or control such invasive feral populations will substantially contribute to minimizing their socioeconomic and environmental impacts.

Predicting the potential implications of perch (Perca fluviatilis) introductions to a biodiversity-rich lake using stable isotope analysis.

Biological invasions, particularly of fish species, significantly threaten aquatic ecosystems. Among these invaders, the introduction of the European perch (Perca fluviatilis) can have particularly detrimental effects on native communities, affecting both ecosystem functioning and human well-being. In this study, carbon and nitrogen stable isotope analysis was employed, using perch originating from five different ecosystems, to model the effects of their hypothetical introduction into Iznik Lake, an economically and ecologically important, biodiversity-rich lake in northern Turkey, to ultimately assess their potential predation impact and competition with native predators. The results revealed that if perch were introduced to the community, they would - considering gape size limitations - primarily prey upon Vimba vimba and Rutilus rutilus, indicating a significant feeding pressure on these species. Furthermore, the study identified a potential overlap and competition for resources between commonly mesopredator perch and the European catfish Silurus glanis, the current top predator in the ecosystem. Both species would occupy top predatory positions, emphasizing the potential disruption of predator-prey dynamics. Our findings underscore the potential ecological repercussions of perch invasions. The selective predation on V. vimba and R. rutilus, with the latter being consumed to a lesser extent by perch, could lead to cascading effects throughout the food web, altering the community structure, and ecosystem dynamics. Additionally, the competition between perch and S. glanis raises concerns about effects on the stability and functioning of the fish community. These results highlight the need for proactive management strategies to mitigate the risk of perch introductions. Strict regulations on the movement and introduction of invasive species, along with comprehensive monitoring, are crucial for preserving native communities and maintaining the ecological integrity of freshwater ecosystems. Our study demonstrates the potential predation impact of perch on vulnerable fish species and the competition with the established apex predator, emphasizing the importance of considering the ecological consequences of perch invasions and informing management decisions to ensure the conservation and sustainability of aquatic ecosystems.

The neglect of nonnative orthopterans as potential invaders: A call for awareness.

Despite the potential ecological and economic impacts of invasive species, there is a dearth of data on the presence, impacts, and management implications of potentially invasive Orthoptera species. This lack of research and inconsistent data, including risk screenings and impact assessments, is especially evident in Europe. Consequently, assessing the status, distribution, and potential threats of nonnative Orthoptera in Europe remains challenging, impeding the development of effective management strategies. To address this gap, we call for increased efforts to collect and curate data on non-native and possibly invasive Orthoptera in Europe. Such efforts will improve our understanding of this order's invasion dynamics, facilitate the identification of priority areas for conservation, and support the development of effective management policies and preventive measures.

Recent advances in availability and synthesis of the economic costs of biological invasions.

Biological invasions are a global challenge that has received insufficient attention. Recently available cost syntheses have provided policy- and decision makers with reliable and up-to-date information on the economic impacts of biological invasions, aiming to motivate effective management. The resultant InvaCost database is now publicly and freely accessible and enables rapid extraction of monetary cost information. This has facilitated knowledge sharing, developed a more integrated and multidisciplinary network of researchers, and forged multidisciplinary collaborations among diverse organizations and stakeholders. Over 50 scientific publications so far have used the database and have provided detailed assessments of invasion costs across geographic, taxonomic, and spatiotemporal scales. These studies have provided important information that can guide future policy and legislative decisions on the management of biological invasions while simultaneously attracting public and media attention. We provide an overview of the improved availability, reliability, standardization, and defragmentation of monetary costs; discuss how this has enhanced invasion science as a discipline; and outline directions for future development.

Keep Your Eggs Away: Ant Presence Reduces Ceratitis capitata Oviposition Behaviour through Trait-Mediated Indirect Interactions.

Alternative methods to achieve sustainable agricultural production while reducing the use of chemical pesticides, such as biological control, are increasingly needed. The exploitation of trait-mediated indirect interactions (TMIIs), in which pests modify their behavior in response to some cues (e.g., pheromones and other semiochemicals) to avoid predation risk, may be a possible strategy. In this study, we tested the effect of TMIIs of two Mediterranean ant species, Crematogaster scutellaris and Tapinoma nigerrimum, on the oviposition behaviour of Ceratitis capitata (Diptera: Tephritidae), one of the world's most economically damaging pests, which attacks fruits. For each ant species, we performed choice experiments using ant-scented and control plums, counting the time spent by medflies on fruits and the number of pupae emerging from them. Results of both ant species tests showed a significantly shorter time spent by ovipositing medflies on ant-exposed plums and a lower number of pupae, when compared to the control group. Our findings highlighted that the semiochemicals released by ants on plums triggered an avoidance behaviour by medfly females, leading to lower oviposition rates. This study contributes to the understanding of indirect ant-pest interactions in Mediterranean agricultural settings and points out the potential of utilising ant-borne semiochemicals in sustainable IPM strategies.

Unveiling the hidden economic toll of biological invasions in the European Union.

Background: Biological invasions threaten the functioning of ecosystems, biodiversity, and human well-being by degrading ecosystem services and eliciting massive economic costs. The European Union has historically been a hub for cultural development and global trade, and thus, has extensive opportunities for the introduction and spread of alien species. While reported costs of biological invasions to some member states have been recently assessed, ongoing knowledge gaps in taxonomic and spatio-temporal data suggest that these costs were considerably underestimated. Results: We used the latest available cost data in InvaCost (v4.1)-the most comprehensive database on the costs of biological invasions-to assess the magnitude of this underestimation within the European Union via projections of current and future invasion costs. We used macroeconomic scaling and temporal modelling approaches to project available cost information over gaps in taxa, space, and time, thereby producing a more complete estimate for the European Union economy. We identified that only 259 out of 13,331 (~ 1%) known invasive alien species have reported costs in the European Union. Using a conservative subset of highly reliable, observed, country-level cost entries from 49 species (totalling US$4.7 billion; 2017 value), combined with the establishment data of alien species within European Union member states, we projected unreported cost data for all member states. Conclusions: Our corrected estimate of observed costs was potentially 501% higher (US$28.0 billion) than currently recorded. Using future projections of current estimates, we also identified a substantial increase in costs and costly species (US$148.2 billion) by 2040. We urge that cost reporting be improved to clarify the economic impacts of greatest concern, concomitant with coordinated international action to prevent and mitigate the impacts of invasive alien species in the European Union and globally. Supplementary Information: The online version contains supplementary material available at 10.1186/s12302-023-00750-3.

Sigmoidal curves reflect impacts and dynamics of aquatic invasive species.

Identifying general patterns and trends underlying the impacts and dynamics of biological invasions has proven elusive for scientists. Recently, the impact curve was proposed as a means to predict temporal impacts of invasive alien species, characterised by a sigmoidal growth pattern with an initial exponential increase, followed by a subsequent rate of decline and approaching a saturation level in the long-term where impact is maximised. While the impact curve has been empirically demonstrated with monitoring data of a single invasive alien species (the New Zealand mud snail, Potamopyrgus antipodarum), broadscale applicability remains to be tested for other taxa. Here, we examined whether the impact curve can adequately describe the invasion dynamics of 13 other aquatic species (within Amphipoda, Bivalvia, Gastropoda, Hirudinea, Isopoda, Mysida, and Platyhelminthes) at the European level, employing multi-decadal time series of macroinvertebrate cumulative abundances from regular benthic monitoring efforts. For all except one tested species (the killer shrimp, Dikerogammarus villosus), the sigmoidal impact curve was strongly supported (R2 > 0.95) on a sufficiently long time-scale. For D. villosus, the impact had not yet reached saturation, likely reflecting the ongoing European invasion. The impact curve facilitated estimation of introduction years and lag phases, as well as parameterisation of growth rates and carrying capacities, providing strong support for the boom-bust dynamics typically observed in several invader populations. These findings suggest that impact can grow rapidly before saturating at a high level, with timely monitoring often lacking for the detection of invasive alien species post-introduction. We further confirm the applicability of the impact curve to determine trends in invasion stages, population dynamics, and impacts of pertinent invaders, ultimately helping inform the timing of management interventions. We hence call for improved monitoring and reporting of invasive alien species over broad spatio-temporal scales to permit further testing of large-scale impact consistencies across various habitat types.

Alien species and climate change drive shifts in a riverine fish community and trait compositions over 35 years.

Alien fish substantially impact aquatic communities. However, their effects on trait composition remain poorly understood, especially at large spatiotemporal scales. Here, we used long-term biomonitoring data (1984-2018) from 31 fish communities of the Rhine river in Germany to investigate compositional and functional changes over time. Average total community richness increased by 49 %: it was stable until 2004, then declined until 2010, before increasing until 2018. Average abundance decreased by 9 %. Starting from 198 individuals/m2 in 1984 abundance largely declined to 23 individuals/m2 in 2010 (-88 %), and then consequently increased by 678 % up to 180 individuals/m2 until 2018. Increases in abundance and richness starting around 2010 were mainly driven by the establishment of alien species: while alien species represented 5 % of all species and 0.1 % of total individuals in 1993, it increased to 30 % (7 species) and 32 % of individuals in 2018. Concomitant to the increase in alien species, average native species richness and abundance declined by 26 % and 50 % respectively. We identified increases in temperature, precipitation, abundance and richness of alien fish driving compositional changes after 2010. To get more insights on the impacts of alien species on fish communities, we used 12 biological and 13 ecological traits to compute four trait metrics each. Ecological trait dispersion increased before 2010, probably due to diminishing ecologically similar native species. No changes in trait metrics were measured after 2010, albeit relative shares of expressed trait modalities significantly changing. The observed shift in trait modalities suggested the introduction of new species carrying similar and novel trait modalities. Our results revealed significant changes in taxonomic and trait compositions following alien fish introductions and climatic change. To conclude, our analyses show taxonomic and functional changes in the Rhine river over 35 years, likely indicative of future changes in ecosystem services.

Sub-lethal doses of imidacloprid alter food selection in the invasive garden ant Lasius neglectus.

Despite several restrictions to their use, neonicotinoid insecticides are still widely employed worldwide. Residual sub-lethal amounts of these chemicals can have detrimental effects on the behavior of non-target insects. Toxic effects on economically important species such as bees have been widely documented, but less is known about their toxic action on other social insects, such as ants. In this study, we assessed the effect of different sub-lethal doses of the neonicotinoid imidacloprid on the ability of colonies of the invasive ant Lasius neglectus to select the most profitable resource. We used Y-shaped mazes having an imidacloprid-polluted or an unpolluted sucrose solution on the two branches. Two sucrose (0.1 M, 0.5 M) and two imidacloprid (1 µg/ml, 10 µg/ml) concentrations were used. In parallel, we evaluated the marking activity of foragers who fed on the same solutions. We found that the 0.1 M sugar solution polluted with 1 µg/ml imidacloprid was significantly more frequently selected in binary choices experiments than the unpolluted resource. Moreover, the ingestion of the same combination of sugar and imidacloprid significantly increased the marking rate of foragers. The higher concentration of the pollutant had lower effects, probably because of the hormesis phenomenon. Results suggest that the lower sub-lethal dose of imidacloprid can lead ants to select again the polluted resource. This "active" selection of the pollutant may magnify the negative effects on the colonies. Due to their ecological role, any impairment of ant survival or behavior may have detrimental cascade effects on the whole ecosystem.

Comparative Analysis of Facial Coloration between Introduced and Source Populations of the Red Wood Ant Formica paralugubris.

The variation in the typical black-reddish color of red wood ants (Formica rufa group) has been recently suggested as a good indicator of habitat quality, being dependent on environmental conditions. However, the relative contribution of external factors and heritability in shaping this trait is poorly investigated. In this study, we compared the facial coloration of workers from four introduced populations of Formica paralugubris with those of the two Alpine populations from which they had been taken. We used a Relative Warp Analysis to describe the variations in the shape of this trait. We expected each introduced population to be more similar to its population of origin if the color pattern was predominantly genetically determined. On the contrary, due to the considerable differences in habitat type and climate between the Alps and the Apennines, we expected to observe differences between the introduced population and their origin population if the coloration was mostly environmentally determined. With one exception that we discuss, the results showed that ants from the two source populations had different phenotypes, and that the introduced populations had a shape similar to the population of origin, suggesting a stable genetic background. Surprisingly, the habitat type seems to have a less clear effect, even if within-population differences suggest the influence of very localized environmental factors. Finally, we found that the facial coloration shape is affected by the ant's size, a result in line with previous studies.

Assessing Molecular Diversity in Native and Introduced Populations of Red Wood Ant Formica paralugubris.

The Formica rufa group comprises several ant species which are collectively referred to as "red wood ants" and play key roles in boreal forest ecosystems, where they are ecologically dominant and greatly influence habitat dynamics. Owing to their intense predatory activity, some of these species are used as biocontrol agents against several forest insect pests and for this aim in Italy, nearly 6000 ant nests were introduced from their native areas in the Alps to several Appeninic sites during the last century. In this work, we assessed and compared the genetic variability and structure of native and introduced populations of F. paralugubris, thus evaluating the extent of genetic drift that may have occurred since the time of introduction, using amplified fragment length polymorphism (AFLP) markers. PCR amplification with a fam_EcoRI-TAC/MseI-ATG primers combination produced a total of 147 scorable bands, with 17 identified as outlier loci. The genetic variation was higher in the introduced population compared to the native ones that, on the other hand, showed a higher diversity between nests. AMOVA results clearly pointed out that the overall genetic structure was dominated by among-worker variation, considering all populations, the Alpine vs. Apennine groups and the comparison among native and related introduced populations (all ranging between 77.84% and 79.84%). Genetic analyses unveiled the existence of six main different groups that do not entirely mirror their geographic subdivision, pointing towards a wide admixture between populations, but, at the same time, rapid diversification of some Apennine populations. Future studies based on high-throughput genomic methods are needed to obtain a thorough understanding of the effects of environmental pressure on the genetic structure and mating system of these populations.

Challenges and a call to action for protecting European red wood ants.

Red wood ants (RWAs) are a group of keystone species widespread in temperate and boreal forests of the Northern Hemisphere. Despite this, there is increasing evidence of local declines and extinctions. We reviewed the current protection status of RWAs throughout Europe and their International Union for the Conservation of Nature (IUCN) threat classification. Only some RWA species have been assessed at a global scale, and not all national red lists of the countries where RWAs are present include these species. Different assessment criteria, inventory approaches, and risk categories are used in different countries, and data deficiency is frequent. Legislative protection is even more complex, with some countries protecting RWAs implicitly together with the wildlife fauna and others explicitly protecting the whole group or particular species. This complexity often occurs within countries, for example, in Italy, where, outside of the Alps, only the introduced species are protected, whereas the native species, which are in decline, are not. Therefore, an international, coordinated framework is needed for the protection of RWAs. This first requires that the conservation target should be defined. Due to the similar morphology, complex taxonomy, and frequent hybridization, protecting the entire RWA group seems a more efficient strategy than protecting single species, although with a distinction between autochthonous and introduced species. Second, an update of the current distribution of RWA species is needed throughout Europe. Third, a protection law cannot be effective without the collaboration of forest managers, whose activity influences RWA habitat. Finally, RWA mounds offer a peculiar microhabitat, hosting a multitude of taxa, some of which are obligate myrmecophilous species on the IUCN Red List. Therefore, RWAs' role as umbrella species could facilitate their protection if they are considered not only as target species but also as providers of species-rich microhabitats.

Las hormigas rojas de la madera (HRM) conforman un grupo de especies clave con amplia distribución en los bosques templados y boreales del Hemisferio Norte. A pesar de lo anterior, cada vez hay más evidencia de su declinación y extinción local. Revisamos el estado actual de protección de las HRM en toda Europa y su clasificación en la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza (UICN). Sólo se han evaluado algunas especies de HRM a escala mundial y no todas las listas rojas nacionales de los países con presencia de HRM incluyen a estas especies. Los diferentes países usan criterios de evaluación, estrategias de inventario y categorías de riesgo distintos, además de que la información deficiente es habitual. La protección legislativa es todavía más compleja pues algunos países protegen implícitamente a las HRM junto con la fauna silvestre y otros protegen explícitamente a todo el grupo o a una especie particular. Esta complejidad ocurre a menudo en los países (por ejemplo: Italia) en donde, fuera de los Alpes, sólo se protege a las especies introducidas, mientras a las especies nativas, que están declinando, no se les protege. Por lo tanto, se requiere un marco de trabajo internacional y coordinado para proteger a las HRM. Esto necesita primero que se defina el objetivo de conservación. Ya que las HRM tienen similitudes morfológicas, una taxonomía compleja e hibridación frecuente, la protección del grupo completo, con la distinción entre las especies autóctonas y las introducidas, parece ser una estrategia más eficiente que la protección de una sola especie. Segundo, se debe actualizar la distribución actual de las HRM en Europa. Tercero, una ley de protección no puede ser efectiva sin la colaboración de los gestores forestales, cuya actividad influye sobre el hábitat de las HRM Finalmente, los montículos de las HRM ofrecen un microhábitat peculiar pues hospedan a una multitud de taxones, algunos de los cuales son especies mirmecófilas obligadas presentes en la Lista Roja de la UICN. Así, el papel de las HRM como especie paraguas podría facilitar su protección si se les considera no sólo como especies diana sino también como proveedoras de microhábitats con riqueza de especies.

Acute and chronic ingestion of polyethylene (PE) microplastics has mild effects on honey bee health and cognition.

The massive use of plastic has contributed to huge quantities of hazardous refuse at a global scale and represents one of the most prominent issues of the Anthropocene. Microplastics (MPs) have been detected in almost all environments and pose a potential threat to a variety of plant and animal species. Many studies have reported a variety of effects, from negligible to detrimental, of MPs to aquatic organisms. Conversely, much less is known about their effect on terrestrial biota, and particularly on animal behavior and cognition. We assessed the oral toxicity of polyethylene (PE) MPs at three different concentrations (0.5, 5, and 50 mg L-1), and at different timescales (1 day and 7 days of exposure) and tested for their effects on survival, food intake, sucrose responsiveness, habituation to sucrose and appetitive olfactory learning and memory in the honey bee Apis mellifera. We found that workers were not completely unaffected by acute and prolonged ingestion of this polymer. A significant effect of PE on bee mortality was found for the highest concentration but not for lower ones. PE affected feeding behavior in a concentration-dependent manner, with bees consuming more food than controls when exposed to low concentration PE. Regarding our behavioral and cognitive experiments, the high concentration PE was found to affect only bees' ability to respond consistently to sucrose but not sucrose sensitivity, habituation to sucrose or learning and memory abilities, even for prolonged exposure to PE. While these last results may look somewhat encouraging, we discussed why caution is warranted before ruling out the possibility that PE particles at environmental concentrations are harmful to honey bees.

Metal accumulation in relation to size and body condition in an all-alien species community.

Metal pollution is one of the main environmental threats in freshwater ecosystems. Aquatic animals can accumulate these substances and transfer them across the food web, posing risks for both predators and humans. Accumulation patterns strongly vary depending on the location, species, and size (which in fish and crayfish is related to age) of individuals. Moreover, high metal concentrations can negatively affect animals' health. To assess the intraspecific relationship between metal accumulation and size and health (proxied by the body condition) of individuals, the concentration of 14 metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn) was analyzed in six alien species from the highly anthropogenically altered Arno River (Central Italy): five fish (Alburnus alburnus, Pseudorasbora parva, Lepomis gibbosus, Ictalurus punctatus, and Silurus glanis) and one crayfish (Procambarus clarkii). We found that in P. clarkii, Cu was negatively related to size, as well as Al in L. gibbosus and Mg for adult I. punctatus. Positive size-dependent relationships were found for Hg in L. gibbosus, Fe in S. glanis, and Cr in juvenile I. punctatus. Only Co and Mg in S. glanis were found to negatively correlate with individual health. Since metal concentrations in animal tissue depend on trade-offs between uptake and excretion, the few significant results suggest different types of trade-offs across different species and age classes. However, only predatory fish species (L. gibbosus, I. punctatus, and S. glanis) presented significant relationships, suggesting that feeding habits are one of the primary drivers of metal accumulation.

Spatio-temporal niche plasticity of a freshwater invader as a harbinger of impact variability.

Invasive alien fishes have detrimental ecological effects on aquatic ecosystems and the services they provide. Impacts from an invasion in a single ecosystem may differ across space and time due to variability in prey availability and environmental conditions. We hypothesize that such variability can be profound, even within a single ecosystem. Stable isotopes analysis (SIA) is commonly used to quantitatively describe the trophic niche of a species. However, spatial and temporal variability in occupied niches are often not incorporated into management strategies and policy options. Here, we used long-term monitoring data to investigate the invasion stage as well as SIA to analyse the trophic niche of the invasive channel catfish Ictalurus punctatus in Lake Kasumigaura (Japan), a long-term ecological research site (LTER), across distant sampling sites and years. We found a significant spatio-temporal variability in relative growth and isotopic niche occupation. Moreover, we defined a new index, the Isotopic Plasticity Index (IPI), which is the ratio between core and total home range of an occupied isotopic niche, to be used as a proxy for the trophic niche stretch or density. We found that this IPI varied considerably, confirming the spatio-temporal variability in trophic niches, suggesting the IPI to be an adequate new isotopic metric. Our results further provide evidence for the existence of variation across invaded landscapes, implying heterogeneous impacts on recipient native communities. Therefore, our work emphasizes the importance of exploring trophic plasticity in feeding ecology and growth as such information enables a better understanding of impacts and can inform the design and implementation of effective management responses.

Small-scale drivers on plant and ant diversity in a grassland habitat through a multifaceted approach.

Semi-natural grasslands are characterized by high biodiversity and require multifaceted approaches to monitor their biodiversity. Moreover, grasslands comprise a multitude of microhabitats, making the scale of investigation of fundamental importance. Despite their wide distribution, grasslands are highly threatened and are considered of high conservation priority by Directive no. 92/43/EEC. Here, we investigate the effects of small-scale ecological differences between two ecosites present within the EU habitat of Community Interest of semi-natural dry grasslands on calcareous substrates (6210 according to Dir. 92/43/EEC) occurring on a Mediterranean mountain. We measured taxonomic and functional diversity of plant and ant communities, evaluating the differences among the two ecosites, how these differences are influenced by the environment and whether vegetation affects composition of the ant community. Our results show that taxonomic and functional diversity of plant and ant communities are influenced by the environment. While vegetation has no effect on ant communities, we found plant and ant community composition differed across the two ecosites, filtering ant and plant species according to their functional traits, even at a small spatial scale. Our findings imply that small-scale monitoring is needed to effectively conserve priority habitats, especially for those that comprise multiple microhabitats.

Combining metal and stable isotope analyses to disentangle contaminant transfer in a freshwater community dominated by alien species.

Freshwater ecosystems are negatively impacted by various pollutants, from agricultural, urban and industrial wastewater, with metals being one of the largest concerns. Moreover, freshwater ecosystems are often affected by alien species introductions that can modify habitats and trophic relationships. Accordingly, the threat posed by metals interacts with those by alien species, since the latter can accumulate and transfer these substances across the food web to higher trophic levels. How metals transfer within such communities is little studied. We analysed the concentration of 14 metals/metalloids (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn, hereafter 'metal(s)') of eight fish and three crustacean species co-existing in the Arno River (Central Italy), most of which were alien. To assess the pathway of contaminants within the community, we coupled metal analysis with carbon and nitrogen stable isotope analysis derived from the same specimens. Crustaceans showed higher metal concentration than fish, except for Cd, Hg and Se that were higher in fish. We found evidence of trophic transfer for six metals (Cd, Cr, Hg, Mg, Se, Zn). Additionally, ontogenetic differences and differences among various fish tissues (muscle, liver, and gills) were found in metals concentration. Considerable biomagnification along the trophic chain was found for Hg, while other metals were found to biodilute. Using stable isotopes and Hg as a third diet tracer, we refined the estimations of consumed preys in the diet previously reconstructed with stable isotope mixing models. Alien species reach high biomass and can both survive to and accumulate high pollutants concentrations, potentially posing a risk for their predators and humans. A combined effect of environmental filtering and increased competition may potentially contribute to the disappearance of native species with lower tolerances.