The ability of rapid range expansion is one of the key determinants of invasive species success. In order to investigate potential drivers behind the rapid spread of invasive species, we explored changes in population characteristics and structure along the invasion pathway of a successful invader in European freshwaters, the signal crayfish (Pacifastacus leniusculus). Diverse population parameters such as relative population abundance, size and sex structure, differences in morphometry and frequency of injuries were compared between signal crayfish population samples at three uniformly distributed segments (approximately 40 km apart) in the lower section of the Mura River, which differed in time since invasion. Examined signal crayfish populations exhibited notable differences, with more recently established populations toward invasion front characterized by lower abundance and male-biased sex ratios, which highlighted males as initial dispersers. We also recorded significant increase in the relative claw size, a competitively advantageous and allometric trait for males, in more recently established populations away from source population. The recorded differences in population structure and male morphometry along the invasion pathway could lead to important clues about dynamics of range expansion and population establishment, highlighting the traits that promote dispersal and better response to local conditions in new habitats. Established differences can also provide insights into the development of targeted management responses aimed at invasive species control.

We test the possibility of a hybrid origin for Chaetopteryx morettii using cross-breeding experiments and molecular analysis. We show that species within the Chaetopteryx villosa group can hybridize, but that C. moretti is not of hybrid origin. We discuss the applicability of our approach for testing ideas on hybrid speciation and detecting hybrids in natural populations, e.g., for conservation purposes.

The diet composition and feeding strategy of native and exotic fish species were studied from May 2005 to February 2006 in three Patagonian low-order streams. A total of 464 fish were caught, which belonged to the exotic species Oncorhynchus mykiss (270), Salmo trutta (177) and the native species Hatcheria macraei (17). The analysis of 336 stomach contents indicated that at the individual level, the three species had a generalized feeding strategy based on benthic invertebrates (Plecoptera, Trichoptera, Coleoptera and Diptera). In the three streams, the widest population niches were observed in winter. There was, however, also a slight tendency toward an increased between-phenotype contribution to the niche width in same season, indicating that a small proportion of individuals within the fish populations specialized by predominantly feeding on a few specific prey species. Hence, the wide population niche widths observed throughout the year were partly a result of mixed individual feeding strategies within the populations. The higher diet overlaps were registered between exotics O. mykiss–S. trutta at Glyn and Carbón, and O. mykiss and the native H. macraei at Manguera, but it changed markedly through the year, perhaps depending on temporal changes in food availability suggesting a competitive coexistence of these species. This is mainly related to the fact that both species changed their food preferences in spring and foraged almost exclusively on Aubertoperla illiesi. This implies that in order to reduce the predation risk or the inter-specific competition for food, the fish species might partition the feeding habitats.

Based on a literature survey and the identification of all available collection material, a checklist and distribution maps for the caddisflies occurring in Flanders were prepared. Of the 126 species that have been recorded, 16 are now extinct in Flanders, while the majority of the remaining species is rare and their populations are often vulnerable due to isolation. Caddisflies only occurred at high oxygen levels and relatively low conductivities and three species assemblages could be recognized. A first group of species lived in stagnant waters and those species tolerated slightly lower oxygen concentrations than species characteristic for running waters. In streams of the Campine region, which are characterized by a low pH and a low conductivity, a second group of species was found. The last group of species mainly occurred in the loamy region, where pH and conductivity are higher. Running waters in other ecoregions mainly contained ubiquist species and did not possess a characteristic species assemblage. Despite the fact that the ecological water quality in Flanders slightly increased during the last few decades, the ecological water quality of most waters is still too low for caddisflies. According to the European Union water framework directive, a good ecological water quality should be obtained in all surface waters. Additional measures to improve the water quality are necessary in order to obtain sustainable populations of the caddisfly species occurring in Flanders.

To understand ostracod distribution and ecology at high altitudes (1659–2889 m a.s.l.), 78 different aquatic sites located in the city of Van were sampled during summer of 2009. A total of 29 ostracod species were recorded in 57 sites. Among the species, Trajancypris laevis (G.W. Müller 1900), is a new report for the Turkish ostracod fauna. First axis of Canonical Correspondence Analysis (CCA) explained about 68% of the relationships between the 13 most abundant species and environmental variables. Four variables (redox potential, habitat type, pH and electrical conductivity) had the greatest effect on species composition (P<0.01). Twenty-six species encountered from 38 stations were restricted between 1659 and 1750 m a.s.l. Above 1750 m a.s.l., the numbers of species were not significantly affected by altitude (P>0.05). Three species (Heterocypris incongruens (Ramdohr, 1808), Ilyocypris bradyi Sars, 1890 and Potamocypris villosa (Jurine, 1820)) occurred extensively from 1650 to 2350 m a.s.l. Spearman rank correlation revealed a negative relationship between Limnocythere inopinata (Baird, 1843) and altitude (r=−0.894, P=0.05), while two species (I. bradyi and Prionocypris zenkeri (Chyzer and Toth, 1858)) had a positive correlation to dissolved oxygen (P=0.05). There was a significantly negative relationship between Ilyocypris inermis Kaufmann, 1900 and electrical conductivity, and H. incongruens showed a significant correlation to station type. Five groups of species were determined by UPGMA analysis. Species in each cluster were grouped according to ecological conditions suitable for them. Results revealed that species ecological tolerances and optimum levels can be species-specific but species with cosmopolitan distributions tend to have high tolerance ranges to different variables, including altitudinal changes.

The aim of this study was to examine morphometric differentiation of gudgeon (Romanogobio and Gobio) species inhabiting the Carpathian Basin, Hungary, with special regard to two recently described species classified into the Gobio genus. For statistical analyses, 23 morphometric and 8 meristic characters were measured on each of the 733 preserved specimens originating from museum collections. The analyses of the standardized morphometric traits revealed low intraspecific variability in all studied species, but varying degrees of interspecific differences. The strongest morphometric differentiation was found in Romanogobio uranoscopus (Agassiz, 1828), which can be characterized by the most special environmental needs. The two allopatric Gobio species showed the weakest morphometric difference. The meristic characters showed high variability in the Romanogobio spp., but did not show significant differences in the two Gobio species. The results show that the morphometric and meristic similarity of the studied Gobio species is definitely high, which preclude reliable identification based on phenotypic characters if only some specimens are available. It seems that the most usable discriminating feature for these species is the localization of the collection site.

Invasive species are a global problem, which costs the world economy billions of dollars and world ecosystems millions of tons of herbicides, pesticides and other cides. Anthropogenic translocation of freshwater copepods associated with early shipping activities was postulated for some time, but was never tested with molecular tools. Here, we examine global molecular diversity of one cyclopoid species, test if the current cosmopolitan distribution is a result of anthropogenic translocation or natural dispersal, and investigate a possibility of cryptic speciation. We use patterns of haplotype frequency of DNA and RNA sequences of four genes (12S, 16S, 18S and cytB) and 11 populations (from England, Scotland, France, Germany, USA, New Zealand and Australia) to test inter- and intrapopulation variability, and three different methods (neighbour joining (NJ), maximum likelihood (ML) and maximum parsimony (MP)) for reconstructing their phylogenetic relationships. They were then tested against two competing hypotheses, and complemented by comparative morphology of microcharacters. Reconstructed phylogenies present strong evidence for anthropogenic translocation, with the same haplotype found in highly disjunct populations in Western Australia, Germany and the USA. Four different clades were revealed with the 12S, 16S and cytB genes, probably representing four cryptic species. Morphological examination of females of two clades contributed a set of microcharacters that can be used in the future taxonomic revision of this species complex. We prove for the first time that cuticular pores and sensilla are homologous structures. This research provides evidence for both homogenization of world freshwater fauna and our inadequate methods of identifying some of its most common species.

Mediterranean temporary ponds (MTPs) are crucial breeding sites for local amphibians, a faunal group in decline in the Mediterranean mainly due to wetland destruction. Although the disappearance of lentic habitats in other regions of the world has been ameliorated by the creation and restoration of wetlands, these tactics remain untested in Mediterranean wetlands. To evaluate the amphibian colonization dynamics of artificial MTPs in the north-eastern Iberian Peninsula, we monitored two artificial MTPs (one in a high-diversity area and the other in a low-diversity area) over 2 years. We selected reference wetlands at each area, and amphibian communities of man-made MTPs were compared to those of reference wetlands. We found that, beginning in the first year, artificial MTPs were a valuable habitat for regional amphibian fauna. Posteriorly, we focused on the reproductive success of the natterjack toad, Bufo calamita. Using a drift fence equipped with pit-fall traps, we measured the abundance of both reproductive adults entering the pond and post-metamorphic individuals exiting the pond. Using mark-recapture methods, we analyzed the time and energy costs associated with reproduction in the artificial MTPs. We observed a highly variable colonization dynamics between sites, between hydroperiods, and within hydroperiods, and these dynamics often depended on meteorological factors. Our results suggest that even at a short timescale, native amphibian species such as B. calamita can benefit from wetland creation in the Mediterranean region.

Using several clonal lineages of Simocephalus vetulus (Cladocera, Daphniidae) as a random sample, we investigated the genetic component of the halotolerance of one brackish and two freshwater populations of this littoral filter feeder. We hypothesized that genotypes from the brackish population were more tolerant than freshwater ones, via adaptation to local environmental conditions. Clonal identity was established by a cost-effective molecular fingerprinting technique (microsatellite-primed polymerase chain reaction (MSP-PCR)). Two distinct methodologies were used to assess cladoceran sensitivity to synthetic-grade sodium chloride (NaCl): (i) standard 48-h acute assays and (ii) 12-h survival time (ST) trials. No correlation was found between acute EC50 and ST values. The sensitivity of brackish and freshwater clones was comparable in terms of acute EC50 (varied from 2.28 to 3.83 g.L−1). On the contrary, genetically determined differential tolerance to NaCl among populations was found for ST: all brackish genotypes, except one, were more resilient (ST>120 min) than freshwater clones (ST<120 min). Bearing in mind that these results were obtained with isolates from the extant population, it is surprising that the range of acute sensitivity of the freshwater and brackish genotypes was similar, and that the only difference between them was the ability of brackish clones to survive longer under high salinity stress (6 g.L−1, in ST trials). We must conclude that the effect of salinity (original environment context) on the selection of genotypes was weaker than we had expected and than other authors have shown for other stressors.

The winter of 2009/2010 was particularly severe in Northern Portugal resulting in higher river flow levels. A study was undertaken to assess the impact of this situation on several populations of freshwater bivalves (e.g., Anodonta anatina, Corbicula fluminea, Margaritifera margaritifera, Potomida littoralis and Unio delphinus) in the catchments of the Rivers Minho, Douro, Tâmega, Tua and Sabor. Massive die-offs occurred for all species in all rivers, resulting in the removal of great numbers and biomass from the riverbed to the adjacent riverbanks, reaching maximum values of 2280 individuals.m−2 and 10 225 g wet weight.m−2, respectively. The invasive Asian clam C. fluminea had both highest density and biomass (however, this invasive bivalve is not dominant in several surveyed sites, and some rivers are still not colonized by this species). Results show that the quantitative and qualitative importance of this carrion transfer to the riverbank should be incorporated in future studies on the assessment of ecosystem function, contributing to a better understanding of the role of freshwater bivalves as resource pulses in adjacent terrestrial habitats. Some of the affected species have conservational importance and these extreme climatic events are predicted to increase in the future. These massive die-off events should be incorporated into management plans and selected restoration measures such as rapid relocation of endangered native mussels back to the riverbed can be easily applied to lessen possible impacts.

Two consecutive earthquakes temporary changed a zooplankton community in a high-mountain Lake Krn (altitude 1383 m a.s.l.). It was dominated by the eurytherm copepod, Cyclops vicinus, until 1998, when the first earthquake hit the lake (EMS=5.6). After the earthquake, the population of C. vicinus collapsed and the thermophilic cladoceran, Ceriodaphnia quadrangula, took over. After the second earthquake in 2004 (EMS=4.0), C. vicinus became untraceable. In 2008, few copepods reappeared and by 2010 they became the sole dominant again. Only Secchi-disc depth showed a statistically significant increase over time, while Ntot, Ptot and temperature showed an increasing trend, yet the relationship was insignificant. To compare multi-parameter properties of the water column, the studied period was divided into Period 1 (before the first earthquake), Period 2 (between earthquakes) and Period 3 (after the second earthquake). A Hotteling T2 test confirmed a statistically significant difference between Periods 1 and 2 & 3 (P<0.01), but not between Periods 2 and 3 (P>0.1). During simple laboratory experiment, specimens of C. vicinus were covered with a thin layer of sediment, to mimic the earthquake's effect on their survival. A hypothesis was that the timing of both earthquakes had been crucial for decimation of C. vicinus population as they re-suspended sediment with hibernating copepodites. As these became subsequently buried they were deprived of a re-activation signal and exposed prolonged anoxic conditions there. C. quadrangula temporary filled the void left by the copepod, which needed 6 years to regain its dominance.

An investigation into bryophyte communities in karst Jankovac Stream (Papuk Nature Park, Croatia) was carried out once a month from July 2008 to June 2009. Samples were taken from two lotic microhabitats: (i) Jankovac Spring (JS), a hypocrenal habitat with dense bryophyte clusters (90% bottom cover) and (ii) Jankovac Waterfall (JW), with scattered bryophyte clusters (50% bottom cover). At the same time, seston samples were collected during the spring as the source site and after the JW, as the outflow site. The goals of this study were to understand the (i) algal, protozoan and metazoan bryophyte community assemblages in these two lotic microhabitats, (ii) influence of environmental factors on the structuring of the bryophyte community and (iii) structure of seston along the longitudinal profile. A total of 172 taxa were determined: 68 algae, 55 protozoa, 24 meiofauna and 25 macroinvertebrates. Statistically significant differences between two microhabitats differing in percentage of bryophyte cover were established testing 13 environmental parameters. In dense bryophyte clusters, community structure was determined by flow velocity and pH, and macroinvertebrates achieved higher diversity and abundance. On the contrary, in scattered bryophyte coverage algae, protozoa and meiofauna reached higher abundance and diversity governed by the amount of suspended organic matter and epiphyton. In contrast to previous studies, the inverse ratio of community diversity and abundance versus percentage of bryophyte cover was established. We assume this to be the result of an enrichment of the scattered bryophyte clusters by upstream seston. Additionally, the effects of anthropogenic hydromorphological disturbance are reflected in macroinvertebrate diversity and abundance reduction.