Non-indigenous species in Northern Europe and the Great Lakes-St. Lawrence River: the importance of geographic origin

Ecosystems all over the world are continuously invaded by new species, which become non-indigenous species (NIS) in the new location. Increasing ship traffic raises the chances for relocations of aquatic species to new regions since shipping is identified as the major transport vector. This dissertation focused on NIS from the North and Baltic Seas and the Great Lakes-St. Lawrence River region. Both regions are connected via frequent transatlantic ship traffic and highly invaded by well documented NIS. Comparing origins of established aquatic NIS in both regions revealed that the systems are highly invaded by species that originate from the Ponto-Caspian region which consists of the Black, Azov and Caspian Seas. Further, observed numbers of established NIS in the two regions were compared to expected numbers of NIS from major donor regions based on the available species pool from donor regions, frequency of shipping transit, and an environmental match between donor and recipient regions. It was discovered that Ponto-Caspian taxa colonized both regions in much higher numbers than expected (Chapter I). A comprehensive study of seven life history traits for each NIS in both regions revealed that certain traits such as dormancy, regeneration and r-strategy are potentially beneficial for invasion success (Chapter II). Global warming as part of a predicted climate change might become a hazard for the survival of some native species, especially in coastal zones which is the habitat of amphipods. Environmental tolerance towards changing temperatures was investigated in three amphipod species and the results revealed that the Ponto-Caspian species Pontogammarus maeoticus has a higher temperature tolerance, especially towards rising temperatures, compared to Gammarus oceanicus, which is native to the Baltic Sea (Chapter III). Hence, with predicted global warming Ponto-Caspian species might be able to compete against native species in the Baltic Sea

Life history traits of aquatic non-indigenous species: freshwater vs. marine habitats

One of the most dominant concepts in invasion ecology is the stage-based invasion model, consisting of transport, introduction, establishment and spread. Many species fail at one of the stages, with propagule pressure (i.e. number of introduced individuals) identified as a principal factor affecting establishment success. Population characteristics such as phenotypic plasticity and beneficial life history traits may facilitate successful transition of species through different stages of the process; however, studies on the latter are not so common and most of those studies focus on terrestrial taxa. In this study, we hypothesized seven life history traits that may be beneficial for invasion success of aquatic species, and determined those traits for established non-indigenous species (NIS) in the North and Baltic Seas (i.e. marine environment) and Great Lakes-St. Lawrence River regions (i.e. freshwater environment). This is the first study that examined certain life history traits of all NIS established in particular regions, as well as compared those traits between marine and freshwater habitats. Our study determined some differences in life history traits between NIS in the marine and freshwater habitats. Those differences were connected to different taxonomic groups that were dominant NIS in these two types of habitats. Furthermore, species originating from different donor regions had also different life history traits. The majority of NIS in both regions were r-strategists. There was a significantly higher number of NIS that were able to reproduce both asexually and sexually and to produce dormant stages in the freshwater than in marine habitat. Finally, as r-strategy, asexual reproduction and dormancy were dominant traits of NIS in the freshwater habitat, freshwater ecosystems may be under greater invasion risk than marine ones, as those traits reduce both demographic and environmental stochasticity during the invasion process

Energy and nitrogenous waste from glutamate/glutamine catabolism facilitates acute osmotic adjustment in non-neuroectodermal branchial cells

Maintenance of homeostasis is one of the most important physiological responses for animals upon osmotic perturbations. Ionocytes of branchial epithelia are the major cell types responsible for active ion transport, which is mediated by energy-consuming ion pumps (e.g., Na+-K+-ATPase, NKA) and secondary active transporters. Consequently, in addition to osmolyte adjustments, sufficient and immediate energy replenishment is essenttableial for acclimation to osmotic changes. In this study, we propose that glutamate/glutamine catabolism and trans-epithelial transport of nitrogenous waste may aid euryhaline teleosts Japanese medaka (Oryzias latipes) during acclimation to osmotic changes. Glutamate family amino acid contents in gills were increased by hyperosmotic challenge along an acclimation period of 72 hours. This change in amino acids was accompanied by a stimulation of putative glutamate/glutamine transporters (Eaats, Sat) and synthesis enzymes (Gls, Glul) that participate in regulating glutamate/glutamine cycling in branchial epithelia during acclimation to hyperosmotic conditions. In situ hybridization of glutaminase and glutamine synthetase in combination with immunocytochemistry demonstrate a partial colocalization of olgls1a and olgls2 but not olglul with Na+/K+-ATPase-rich ionocytes. Also for the glutamate and glutamine transporters colocalization with ionocytes was found for oleaat1, oleaat3, and olslc38a4, but not oleaat2. Morpholino knock-down of Sat decreased Na+ flux from the larval epithelium, demonstrating the importance of glutamate/glutamine transport in osmotic regulation. In addition to its role as an energy substrate, glutamate deamination produces NH4+, which may contribute to osmolyte production; genes encoding components of the urea production cycle, including carbamoyl phosphate synthetase (CPS) and ornithine transcarbamylase (OTC), were upregulated under hyperosmotic challenges. Based on these findings the present work demonstrates that the glutamate/glutamine cycle and subsequent transepithelial transport of nitrogenous waste in branchial epithelia represents an essential component for the maintenance of ionic homeostasis under a hyperosmotic challenge

Energy metabolism and regeneration impaired by seawater acidification in the infaunal brittlestar, Amphiura filiformis

Seawater acidification due to anthropogenic release of CO2 as well as the potential leakage of pure CO2 from sub-seabed carbon capture storage sites (CCS) may impose a serious threat to marine organisms. Although infaunal organisms can be expected to be particularly impacted by decreases in seawater pH, due to naturally acidified conditions in benthic habitats, information regarding physiological and behavioral responses is still scarce. Determination of pO2 and pCO2 gradients within the burrows of the brittlestar Amphiura filiformis during environmental hypercapnia demonstrated that besides hypoxic conditions, increases of environmental pCO2 are additive to the already high pCO2 (up to 0.08 kPa) within the burrows. In response to up to 4 weeks exposure to pH 7.3 (0.3 kPa pCO2) and pH 7.0 (0.6 kPa pCO2), metabolic rates of A.filiformis were significantly reduced in pH 7.0 treatments accompanied by increased ammonium excretion rates. Gene expression analyses demonstrated significant reductions of acid-base (NBCe and AQP9) and metabolic (G6PDH, LDH) genes. Determination of extracellular acid-base status indicated an uncompensated acidosis in CO2 treated animals, which could explain depressed metabolic rates. Metabolic depression is associated with a retraction of filter feeding arms into sediment burrows. Regeneration of lost arm tissues following traumatic amputation is associated with significant increases in metabolic rate, and hypercapnic conditions (pH 7.0, 0.6 KPa) dramatically reduce the metabolic scope for regeneration reflected in 80% reductions in regeneration rate. Thus, the present work demonstrates that elevated seawater pCO2 significantly affects the environment and the physiology of infaunal organisms like A. filiformis

Importance of geographic origin for invasion success: A case study of the North and Baltic Seas versus the Great Lakes-St. Lawrence River region

Recently, several studies indicated that species from the Ponto-Caspian region may be evolutionarily predisposed to become nonindigenous species (NIS); however, origin of NIS established in different regions has rarely been compared to confirm these statements. More importantly, if species from certain area/s are proven to be better colonizers, management strategies to control transport vectors coming from those areas must be more stringent, as prevention of new introductions is a cheaper and more effective strategy than eradication or control of established NIS populations. To determine whether species evolved in certain areas have inherent advantages over other species in colonizing new habitats, we explored NIS established in the North and Baltic Seas and Great Lakes–St. Lawrence River regions—two areas intensively studied in concern to NIS, highly invaded by Ponto-Caspian species and with different salinity patterns (marine vs. freshwater). We compared observed numbers of NIS in these two regions to expected numbers of NIS from major donor regions. The expected numbers were calculated based on the available species pool from donor regions, frequency of shipping transit, and an environmental match between donor and recipient regions. A total of 281 NIS established in the North and Baltic Seas and 188 in the Great Lakes–St. Lawrence River. Ponto-Caspian taxa colonized both types of habitats, saltwater areas of the North and Baltic Seas and freshwater of the Great Lakes–St. Lawrence River, in much higher numbers than expected. Propagule pressure (i.e., number of introduced individuals or introduction effort) is of great importance for establishment success of NIS; however in our study, either shipping vector or environmental match between regions did not clarify the high numbers of Ponto-Caspian taxa in our study areas. Although we cannot exclude the influence of other transport vectors, our findings suggest that the origin of the species plays an important role for the predisposition of successful invaders

Salinity dependence of recruitment success of the sea star Asterias rubens in the brackish western Baltic Sea

Salinity strongly influences development and distribution of the sea star Asterias rubens. In Kiel Fjord, located in the western Baltic Sea, A. rubens is the only echinoderm species and one of the main benthic predators controlling blue mussel (Mytilus edulis) abundance. However, Kiel Fjord with an average salinity of about 15 is located close to the eastern distribution boundary of A. rubens in the Baltic Sea. In this study, we combined field and laboratory investigations to test whether the salinity of Kiel Fjord is high enough to enable successful development of A. rubens. Sea star eggs were fertilized in vitro, and development was monitored in the laboratory at four salinities (9, 12, 15 and 18) for 10 weeks. At a salinity of 9, development ceased prior to the blastula stage. At a salinity of 12, no larvae reached metamorphosis. At higher salinities, larvae developed normally and metamorphosed into juvenile sea stars. Abundances of A. rubens larvae and settled juveniles were also observed in Kiel Fjord and correlated to salinity values measured from March until June during 6 years (2005–2010). Results revealed high A. rubens settlement rates only in 2009, the year when salinity was the highest and least variable during the period of spawning and larval development. It appears that only years with high and stable salinities permit recruitment of A. rubens in Kiel Fjord. Projected desalination of the Baltic Sea could shift the distribution of A. rubens in the western Baltic Sea north-westwards and may lead to local extinction of a keystone species of the benthic ecosystem

What's hot in conservation biogeography in a changing climate? Going beyond species range dynamics

International audienceIn recent decades Earth's rapidly changing climate, driven by anthropogenic greenhouse gas emissions, has affected species distributions and phenology, ecological communities and ecosystem processes, effects that are increasingly being observed globally (Allen et al., 2010; Doney et al., 2012; Franklin, Serra‐Diaz, Syphard, & Regan, 2016; Parmesan, 2006; Walther et al., 2002). Pleistocene shifts in species ranges during glacial–interglacial transitions reveal large‐scale biome shifts and no‐analog species assemblages (MacDonald et al., 2008; Nolan et al., 2018; Williams & Jackson, 2007); the pace of current anthropogenic warming outstrips past changes in the Earth system and climate, however, leading to new climate novelties and ecological communities (Ordonez, Williams, & Svenning, 2016). Global scientific consensus now emphasizes that global warming should be kept to 1.5°C to avoid catastrophic changes in ecosystems and the services they provide to people (IPCC, 2018), and climate change threats to biodiversity are being prioritized in international policy response (Ferrier et al., 2016)

Influence of auto-organization and fluctuation effects on the kinetics of a monomer-monomer catalytic scheme

We study analytically kinetics of an elementary bimolecular reaction scheme of the Langmuir-Hinshelwood type taking place on a d-dimensional catalytic substrate. We propose a general approach which takes into account explicitly the influence of spatial correlations on the time evolution of particles mean densities and allows for the analytical analysis. In terms of this approach we recover some of known results concerning the time evolution of particles mean densities and establish several new ones.Comment: Latex, 25 pages, one figure, submitted to J. Chem. Phy

Diversity and distribution of genetic variation in gammarids: Comparing patterns between invasive and non-invasive species

© 2017 Published by John Wiley & Sons Ltd. Biological invasions are worldwide phenomena that have reached alarming levels among aquatic species. There are key challenges to understand the factors behind invasion propensity of non-native populations in invasion biology. Interestingly, interpretations cannot be expanded to higher taxonomic levels due to the fact that in the same genus, there are species that are notorious invaders and those that never spread outside their native range. Such variation in invasion propensity offers the possibility to explore, at fine-scale taxonomic level, the existence of specific characteristics that might predict the variability in invasion success. In this work, we explored this possibility from a molecular perspective. The objective was to provide a better understanding of the genetic diversity distribution in the native range of species that exhibit contrasting invasive propensities. For this purpose, we used a total of 784 sequences of the cytochrome c oxidase subunit I of mitochondrial DNA (mtDNA-COI) collected from seven Gammaroidea, a superfamily of Amphipoda that includes species that are both successful invaders (Gammarus tigrinus, Pontogammarus maeoticus, and Obesogammarus crassus) and strictly restricted to their native regions (Gammarus locusta, Gammarus salinus, Gammarus zaddachi, and Gammarus oceanicus). Despite that genetic diversity did not differ between invasive and non-invasive species, we observed that populations of non-invasive species showed a higher degree of genetic differentiation. Furthermore, we found that both geographic and evolutionary distances might explain genetic differentiation in both non-native and native ranges. This suggests that the lack of population genetic structure may facilitate the distribution of mutations that despite arising in the native range may be beneficial in invasive ranges. The fact that evolutionary distances explained genetic differentiation more often than geographic distances points toward that deep lineage divergence holds an important role in the distribution of neutral genetic diversity