A horizon scan exercise for aquatic invasive alien species in Iberian inland waters.

As the number of introduced species keeps increasing unabatedly, identifying and prioritising current and potential Invasive Alien Species (IAS) has become essential to manage them. Horizon Scanning (HS), defined as an exploration of potential threats, is considered a fundamental component of IAS management. By combining scientific knowledge on taxa with expert opinion, we identified the most relevant aquatic IAS in the Iberian Peninsula, i.e., those with the greatest geographic extent (or probability of introduction), severe ecological, economic and human health impacts, greatest difficulty and acceptability of management. We highlighted the 126 most relevant IAS already present in Iberian inland waters (i.e., Concern list) and 89 with a high probability of being introduced in the near future (i.e., Alert list), of which 24 and 10 IAS, respectively, were considered as a management priority after receiving the highest scores in the expert assessment (i.e., top-ranked IAS). In both lists, aquatic IAS belonging to the four thematic groups (plants, freshwater invertebrates, estuarine invertebrates, and vertebrates) were identified as having been introduced through various pathways from different regions of the world and classified according to their main functional feeding groups. Also, the latest update of the list of IAS of Union concern pursuant to Regulation (EU) No 1143/2014 includes only 12 top-ranked IAS identified for the Iberian Peninsula, while the national lists incorporate the vast majority of them. This fact underlines the great importance of taxa prioritisation exercises at biogeographical scales as a step prior to risk analyses and their inclusion in national lists. This HS provides a robust assessment and a cost-effective strategy for decision-makers and stakeholders to prioritise the use of limited resources for IAS prevention and management. Although applied at a transnational level in a European biodiversity hotspot, this approach is designed for potential application at any geographical or administrative scale, including the continental one.

Multispecies fishways in a Mediterranean river: Contributions as migration corridors and compensatory habitat for fish.

River connectivity is essential for the resilience of fish assemblages and populations and is a priority goal to reach good ecological status for river systems. Increasing knowledge on the functionality of restoration tools such as fishways is relevant for future management strategies. The present two-year assessment showed clear ecological contributions of different types of multispecies fishways in the fish assemblage of a strongly modified Mediterranean-type river. Just after their implementation, early and extended use by dominant river-resident fish of both naturelike and technical fishways were observed. All fishways were used in different seasons, especially during the migratory periods by potamodromous cyprinids, suggesting a possible use as migration corridors. Fishways also may provide compensatory habitats for small and juvenile individuals throughout the annual cycles, mostly for rheophilic fish inside nature-like bypasses and for limnophilics inside technical types. Fluvial habitat characteristics and lower flow variability inside the fishways could favour their role as a fish refuge, mainly to juveniles of cyprinids, in heavily regulated rivers where large flow fluctuations occurred. Nature-like fishways could be a better option to function as a compensatory habitat for rheophilic cyprinids in Mediterranean-type Rivers, even more because their use by large nonnative limnophilics seems to be very scarce. However, technical fishways could offer the opportunity to establish control traps of some nonnative fish, which could be of interest to reduce the risk of spreading invasive fish. Therefore, fish ecology and local hydrology should drive the decision between the types to implement. The obtained information on the ecological functionality of multispecies fishways should be considered for applying successful river restorations that are demanded by water and wildlife management schemes (e.g., the European Water Framework Directive).

Functional response of fish assemblage to multiple stressors in a highly regulated Mediterranean river system.

Mediterranean rivers are characterised by strong environmental constrains and species-poor, highly endemic fish fauna. In Europe, these systems are exposed to multiple stressors due to extensive human activities. Studies on the effects of some stressors on riverine fish are available but complex responses of fish assemblages to interplay of flow alteration with physical habitat changes and invasive species have not been evaluated up to date. This study analysed the response of functional diversity of fish assemblages to multiple stressors in the Segura River system in the southern Spain. Fish assemblages were sampled in 16 sites in two consecutive periods (2009-2010 and 2013-2015). Subsequently, we assessed the responses of functional specialisation, originality and entropy (based on nine functional traits and abundances) as well as species richness and abundance to interplay of flow regime alteration and ecological status, fragmentation as well as non-native species abundance across spatial and temporal scales. The governing role of flow regime in structuring fish assemblage was superimposed on physical habitat changes, water quality deterioration and fragmentation as well as the presence of non-native fish species. We found an increase of species richness and abundance but decrease of functional specialisation and originality in river reaches with high level of base flow and more stable hydrological conditions. Opposite pattern was observed in reaches with severe reduction of base flow and marked inversion in the seasonal pattern of high and low flows. We postulate that the use of tools that consider the functional identity of the species as method to assess the effects of environmental alterations on fish biodiversity could improve conservation measures for Mediterranean fish fauna. Furthermore, design flows that mimic natural flow regime patterns characteristic for Mediterranean rivers are a promising tool to provide environmental conditions that would favour native fish within the assemblage and benefit their conservation.

Phylogeography and Population Genetic Analyses in the Iberian Toothcarp (Aphanius iberus Valenciennes, 1846) at Different Time Scales.

Secondary freshwater fish species inhabiting fluctuating and extreme environments are susceptible to changes in dispersion, effective population size, and genetic structure. The Iberian toothcarp Aphanius iberus is an endemic cyprinodontid of the Iberian Peninsula restricted to brackish water of salt marshes and coastal lagoons on the eastern Spanish Mediterranean coast. In this study, we analyzed mitochondrial cytochrome b (cyt b) DNA and microsatellite variation to evaluate ways in which the processes of extinction, dispersal, and colonization of A. iberus across its geographic distribution have affected its population genetic structure over time and space. The A. iberus network reconstruction indicated subtle levels of phylogeographic structuring. This, combined with substantial mitochondrial DNA (mtDNA) genetic diversity, suggests that Pleistocene glaciations had a lesser effect on the demographic structure of its populations than was the case for Iberian freshwater species with a similar distribution. Haplotype network, hierarchical analysis of molecular variance, and pairwise ΦST comparisons involving some Levantine samples showed a relatively high degree of mtDNA differentiation, which could be explained by historical isolation of the Villena Lagoon population. Conversely, significant genetic differentiation that follows an isolation-by-distance pattern, and a reduction in Ne though time was detected with microsatellites, suggesting extensive habitat fragmentation on the Mediterranean coast of the Iberian Peninsula over the past hundreds of years. At a smaller geographical scale (Mar Menor Lagoon), habitat fragmentation, probably due to human activity, appears to have resulted in substantially reduced migration and increased genetic drift, as shown by expanded genetic differentiation of populations.

Understanding of the impact of chemicals on amphibians: a meta-analytic review.

Many studies have assessed the impact of different pollutants on amphibians across a variety of experimental venues (laboratory, mesocosm, and enclosure conditions). Past reviews, using vote-counting methods, have described pollution as one of the major threats faced by amphibians. However, vote-counting methods lack strong statistical power, do not permit one to determine the magnitudes of effects, and do not compare responses among predefined groups. To address these challenges, we conducted a meta-analysis of experimental studies that measured the effects of different chemical pollutants (nitrogenous and phosphorous compounds, pesticides, road deicers, heavy metals, and other wastewater contaminants) at environmentally relevant concentrations on amphibian survival, mass, time to hatching, time to metamorphosis, and frequency of abnormalities. The overall effect size of pollutant exposure was a medium decrease in amphibian survival and mass and a large increase in abnormality frequency. This translates to a 14.3% decrease in survival, a 7.5% decrease in mass, and a 535% increase in abnormality frequency across all studies. In contrast, we found no overall effect of pollutants on time to hatching and time to metamorphosis. We also found that effect sizes differed among experimental venues and among types of pollutants, but we only detected weak differences among amphibian families. These results suggest that variation in sensitivity to contaminants is generally independent of phylogeny. Some publication bias (i.e., selective reporting) was detected, but only for mass and the interaction effect size among stressors. We conclude that the overall impact of pollution on amphibians is moderately to largely negative. This implies that pollutants at environmentally relevant concentrations pose an important threat to amphibians and may play a role in their present global decline.

Behavioral responses of the Iberian waterfrog, Pelophylax perezi (Seoane, 1885), to three nitrogenous compounds in laboratory conditions.

Several studies have assessed the effects of nitrogenous compounds on amphibian behavior. However, few have focused on the effects of their combination with other stressors or on the variation of the response to pollutants among populations. We analyzed the effect of nitrogenous compounds (NH(4)(+); NO(2)(-); NO(3)(-), both alone and in combination) on larval behavior (activity level and location in the water column) in four populations of Pelophylax perezi naturally exposed to different levels of eutrophication. Larval activity was highest and use of the bottom of the experimental beaker was lowest at lower concentrations of nitrogenous compounds acting singly, these responses being minimal and maximal, respectively, at both control and higher concentrations. This pattern appears to fit to an hormetic response. Additionally, the combination of nitrogenous compounds affected more severely the response variables than when ammonium or nitrite acted singly according to an additive model. Populations inhabiting highly polluted aquatic habitats marginally showed higher activity level than the populations from less polluted environments, especially when larvae were exposed to ammonium or when nitrite appeared in combination with other nitrogen forms. Levels of activity correlated positively with larval final mass. Moreover, for similar levels of activity, larvae from polluted populations had higher growth rates than those coming from reference populations which suggests interdemic differences in behavioral sensitivity to nitrogenous pollutants.

Populational divergence in the impact of three nitrogenous compounds and their combination on larvae of the frog Pelophylax perezi (Seoane, 1885).

Pollution by nitrogenous compounds is a putative stressful factor that may be causally linked to the decline of amphibians. One way to understand the potentially detrimental consequences of eutrophication on amphibian populations is to investigate variation among populations differing in exposure to nitrogen, this variation potentially indicating evolutionary potential to cope with this stressor. We have examined the effect of nitrogenous compounds (NH(4)(+); NO(2)(-); NO(3)(-), both alone and in combination) on fitness-related larval traits in four populations of Pelophylax perezi naturally exposed to different degrees of eutrophication. The results indicate that both survival and larval final size decrease at higher concentrations of these compounds, either singly or in combination. Additionally, the nitrogenous compounds were more lethal and larval food consumption and final mass were significantly reduced when they were exposed to combinations of compounds. Populations inhabiting highly polluted aquatic environments tolerated higher levels of nitrogenous compounds and showed higher survival rates and larger final size than the populations of less polluted environments, suggesting the potential to adapt to increased nitrogenous contamination in this species.

Analysis of the avoidance of nitrogen fertilizers in the water column by juvenile Iberian water frog, Pelophylax perezi (Seoane, 1885), in laboratory conditions.

In an experiment carried out in the laboratory in beakers, the avoidance of ammonium chloride, isolated or combined with sodium nitrite and sodium nitrate, in aquatic habitat by froglets of Pelophylax perezi was studied. The results obtained suggest that nitrogen polluted treatments were not avoided by froglets of the studied species. However, despite the non-avoidance of the aquatic environment as a consequence of the presence of nitrogen compounds, significant inter-individual variation in treatment avoidance was detected. Although these results are not conclusive, they would suggest that froglets of P. perezi might occupy habitats which contain high levels of organic compounds and that they differ in their level of avoidance to fertilizer exposure.