On the occurrence of three non-native cichlid species including the first record of a feral population of Pelmatolapia (Tilapia) mariae (Boulenger, 1899) in Europe

Investigation on the Global Distribution of Invasive Fish Species, Convict Cichlid Amatitlania Nigrofasciata (Perciformes, Cichlidae) Over the Past Years with Emphasis on Iranian Inland Waters

The aim of this study was to investigate the global distribution of a non-indigenous and invasive fish species, the convict cichlid Amatitlania nigrofasciata, over time, with an emphasis on the inland waters of Iran. The results showed that the distribution range of the convict cichlid was initially based in Central America. Then, the distribution range of this species expanded to parts of North America. Finally, this fish species was introduced to other parts of the world such as Australia, Israel, Italy, Colombia, Germany, Peru, Slovakia, Japan, Indonesia, the Philippines, and Iran due to its extensive ability to spread. So far the presence of A. nigrofasciata has been reported in two domestic basins in Iran, namely Hormuz and Namak Lake. This study indicated that the distribution range of this species is not currently wide, but it is likely to expand towards the central plateau and southern parts of Iran.

Consistent Behavioral Syndrome Across Seasons in an Invasive Freshwater Fish

Understanding the linkage between behavioral types and dispersal tendency has become a pressing issue in light of global change and biological invasions. Here, we explore whether dispersing individuals exhibit behavioral types that differ from those remaining in the source population. We investigated a feral population of guppies (Poecilia reticulata) that undergoes a yearly range shift cycle. Guppies are among the most widespread invasive species in the world, but in temperate regions these tropical fish can only survive in winter-warm freshwaters. Established in a thermally-altered stream in Germany, guppies are confined to a warm-water influx in winter, but can spread to peripheral parts as these become thermally accessible. We sampled fish from the source population and a winter-abandoned site in March, June and August. Fish were tested for boldness, sociability and activity involving open-field tests including interactions with a robotic social partner. Guppies differed consistently among each other in all three traits within each sample. Average trait expression in the source population differed across seasons, however, we could not detect differences between source and downstream population. Instead, all populations exhibited a remarkably stable behavioral syndrome between boldness and activity despite strong seasonal changes in water temperature and associated environmental factors. We conclude that random drift (opposed to personality-biased dispersal) is a more likely dispersal mode for guppies, at least in the investigated stream. In the face of fluctuating environments, guppies seem to be extremely effective in keeping behavioral expressions constant, which could help explain their successful invasion and adaptation to new and disturbed habitats.

Out of the Blue: The Failure of the Introduced Sea Anemone Sagartia elegans (Dalyell, 1848) in Salem Harbor, Massachusetts

Failed invasions can be a key component for understanding and controlling introduced populations because understanding mechanisms behind failures can improve effective controls. In 2000, the non-native sea anemone Sagartia elegans was first found in Salem, Massachusetts, and it recolonized each summer. No individuals of S. elegans have been found after 2010, despite intensive search efforts. A mismatch between the species' thermal tolerance and winter water temperature is the most likely mechanism for this failed invasion. In both laboratory- and field-based temperature growth studies, S. elegans began regressing at 11 °C, stopped asexually reproducing at 9 °C, and died by 4 °C. These temperatures are above the average winter sea surface temperature in the Gulf of Maine, therefore suggesting that S. elegans requires a warm-water refuge. Another potential contributor to the disappearance of S. elegans is low genetic diversity as a result of establishment of only females (likely clones) and no males.

Thermal effluents from power plants boost performance of the invasive clam Corbicula fluminea in Ireland's largest river

Elevated temperatures due to anthropogenic activities can improve the performance of non-native species that are adapted to higher temperatures than resident species. Ecosystems may experience higher temperature due to global stressors, such as climate change, or local stressors, including thermal effluents and urban heat islands. Using field surveys of population density and body size of the highly invasive and hot-adapted clam Corbicula fluminea in and out of two thermal effluents from power plants along the River Shannon, Ireland, we tested the hypothesis that C. fluminea performs better in thermal plumes. Shell length and body mass of C. fluminea in thermal effluents were 1.8 and 4.4 times higher, respectively, compared with adjacent unheated river sections. Density of C. fluminea was 13.7 times higher in heated, compared with unheated river reaches, leading to an increase in combined biomass per unit area of >50-fold. Our temperature data suggest an up to 2.5-fold increase of degree-days for growth and up to 5.2-fold increase of degree-days for larval incubation in the thermal plumes in River Shannon, compared with unheated conditions. Through enlarged body size, the elevated temperatures likely increase fecundity within the plumes. These findings illustrate that, in temperate climates, thermal plumes can form sanctuaries, where C. fluminea likely alters habitat, outpaces competitors and potentially dominates the energy flow through food webs. Furthermore, thermal plumes can act as stepping-stones and propagule banks for further proliferation of C. fluminea and other warm-adapted invaders.

Small-scale phenotypic differentiation along complex stream gradients in a non-native amphipod

Background

Selective landscapes in rivers are made up by an array of selective forces that vary from source to downstream regions or between seasons, and local/temporal variation in fitness maxima can result in gradual spatio-temporal variation of phenotypic traits. This study aimed at establishing freshwater amphipods as future model organisms to study adaptive phenotypic diversification (evolutionary divergence and/or adaptive plasticity) along stream gradients.

Methods

We collected Gammarus roeselii from 16 sampling sites in the Rhine catchment during two consecutive seasons (summer and winter). Altogether, we dissected n = 1648 individuals and quantified key parameters related to morphological and life-history diversification, including naturally selected (e.g., gill surface areas) as well as primarily sexually selected traits (e.g., male antennae). Acknowledging the complexity of selective regimes in streams and the interrelated nature of selection factors, we assessed several abiotic (e.g., temperature, flow velocity) and biotic ecological parameters (e.g., conspecific densities, sex ratios) and condensed them into four principal components (PCs).

Results

Generalized least squares models revealed pronounced phenotypic differentiation in most of the traits investigated herein, and components of the stream gradient (PCs) explained parts of the observed differences. Depending on the trait under investigation, phenotypic differentiation could be ascribed to variation in abiotic conditions, anthropogenic disturbance (influx of thermally polluted water), or population parameters. For example, female fecundity showed altitudinal variation and decreased with increasing conspecific densities, while sexual dimorphism in the length of male antennae—used for mate finding and assessment—increased with increasing population densities and towards female-biased sex ratios.

Conclusions

We provide a comprehensive protocol for comparative analyses of intraspecific variation in life history traits in amphipods. Whether the observed phenotypic differentiation over small geographical distances reflects evolutionary divergence or plasticity (or both) remains to be investigated in future studies. Independent of the mechanisms involved, variation in several traits is likely to have consequences for ecosystem functions. For example, leaf-shredding in G. roeselii strongly depends on body size, which varied in dependence of several ecological parameters.

Electronic supplementary material

The online version of this article (10.1186/s12983-019-0327-8) contains supplementary material, which is available to authorized users.