Is salinity an obstacle for biological invasions?

Abstract

Our study revealed that all tested populations tolerate wide ranges of salinity, however, different patterns arose among species from different regions. Ponto-Caspian taxa showed lower mortality in fresh water, while Northern European taxa showed lower mortality in fully marine conditions. Genetic analyses showed evolutionary divergence among species from different regions. Due to the geological history of the two regions, as well as high tolerance of Ponto-Caspian species to fresh water, whereas Northern European species are more tolerant of fully marine conditions, we suggest that species originating from the Ponto-Caspian and Northern European regions may be adapted to freshwater and marine environments, respectively. Consequently, the perception that Ponto-Caspian species are more successful colonizers might be biased by the fact that areas with highest introduction frequency of NIS (i.e., shipping ports) are environmentally variable habitats which often include freshwater conditions that cannot be tolerated by euryhaline taxa of marine origin. K E Y W O R D Sfreshwater origin, Gammaroidea, marine origin, nonindigenous species, Ponto-Caspian species, salinity tolerance --

Environmental tolerance of three gammarid species with and without invasion record under current and future global warming scenarios

“…In addition, several previous studies reported that G. tigrinus can tolerate temperatures up to 30°C in brackish environments, and it thrives in heavily polluted waters (Pinkster et al., ; Ruoff, ; Savage, ; Wijnhoven, Van Riel, & van der Velde, ), while Paiva et al. () determined different salinity tolerance among populations of that species and seven others. In the population used in our experiments, dark spots were regularly observed on animals.…”

“…However, Paiva et al. () reported different salinity tolerance among populations for the same eight gammarid species indicating that neutral genetic markers, such as mtDNA‐COI, are not able to detect population adaptation to different salinities and genome‐wide screening, particularly of coding regions, is necessary to determine adaptation to local environmental conditions. While, we are not aware of any study connecting temperature tolerance and populations for any species, we believe that the same would apply for adaptation to different temperature tolerance.…”

“…However, the species is a highly successful invader that established in the majority of Northern European freshwater and brackish habitats, where in some areas, it locally replaced or reduced abundance of native species, such as G. duebeni, G. salinus and G. zaddachi, and altered community compositions (Jänes et al, 2015;Kelly, Muirhead, Heath, & MacIsaac, 2006;Kotta et al, 2011Kotta et al, , 2013Pinkster et al, 1992). In addition, several previous studies reported that G. tigrinus can tolerate temperatures up to 30°C in brackish environments, and it thrives in heavily polluted waters (Pinkster et al, 1977;Ruoff, 1968;Savage, 1982;Wijnhoven, Van Riel, & van der Velde, 2003), while Paiva et al (2018) determined different salinity tolerance among populations of that species and seven others. In the population used in our experiments, dark spots were regularly observed on animals.…”

“…It is also widespread along the coasts of the North Atlantic up to subarctic regions (Bulnheim, 1979;Segerstråle, 1947). It was not reported outside its native range (Paiva et al, 2018); (b) P. maeoticus is native to the Ponto-Caspian region in salinities from 0.5 to 30 g/kg (Paiva et al, 2018). It is NIS in freshwater areas of Turkey, but not in the Baltic Sea (Casties et al, 2016;Ozbek, 2011); and G. tigrinus is native to the Atlantic coast of North America in salinities from <0.5 to 30 g/kg (Paiva et al, 2018), while it is NIS in Northern Europe including the Baltic Sea (Daunys & Zettler, 2006).…”

“…It was not reported outside its native range (Paiva et al, 2018); (b) P. maeoticus is native to the Ponto-Caspian region in salinities from 0.5 to 30 g/kg (Paiva et al, 2018). It is NIS in freshwater areas of Turkey, but not in the Baltic Sea (Casties et al, 2016;Ozbek, 2011); and G. tigrinus is native to the Atlantic coast of North America in salinities from <0.5 to 30 g/kg (Paiva et al, 2018), while it is NIS in Northern Europe including the Baltic Sea (Daunys & Zettler, 2006). During the period until the experiments commenced, all three species were kept at the temperature and salinity of their respective collection sites (i.e., 16°C, 16 g/kg for G. oceanicus, 18°C, 10 g/kg for P. maeoticus and 16°C, 10 g/kg for G. tigrinus).…”