Out of the Black Sea: Phylogeography of the Invasive Killer Shrimp Dikerogammarus villosus across Europe

The amphipod Dikerogammarus villosus has colonized most of the European main inland water bodies in less than 20 years, having deteriorating effect on the local benthic communities. Our aim was to reveal the species phylogeography in the native Black Sea area, to define the source populations for the colonization routes in continental Europe and for the newly established UK populations. We tested for the loss of genetic diversity between source and invasive populations as well as along invasion route. We tested also for isolation by distance. Thirty three native and invasive populations were genotyped for mtDNA (COI, 16S) and seven polymorphic nuclear microsatellites to assess cryptic diversity (presence of deeply divergent lineages), historical demography, level of diversity within lineage (e.g., number of alleles), and population structure. A wide range of methods was used, including minimum spanning network, molecular clock, Bayesian clustering and Mantel test. Our results identified that sea level and salinity changes during Pleistocene impacted the species phylogeography in the Black Sea native region with four differentiated populations inhabiting, respectively, the Dnieper, Dniester, Danube deltas and Durungol liman. The invasion of continental Europe is associated with two sources, i.e., the Danube and Dnieper deltas, which gave origin to two independent invasion routes (Western and Eastern) for which no loss of diversity and no isolation by distance were observed. The UK population has originated in the Western Route and, despite very recent colonization, no drastic loss of diversity was observed. The results show that the invasion of the killer shrimp is not associated with the costs of loosing genetic diversity, which may contribute to the success of this invader in the newly colonized areas. Additionally, while it has not yet occurred, it might be expected that future interbreeding between the genetically diversified populations from two independent invasion routes will potentially even enhance this success

Does invader like invader? Feeding preferences of an alien Ponto-Caspian goby towards indigenous and non-indigenous amphipod prey

When non-native species appear in a new ecosystem, it may sufficiently affect native communities i.a. through interactions with native as well as other alien species. The „invasional meltdown“ hypothesis states that the presence of non-indigenous species facilitates the introduction and establishment of the other non-native species. A series of laboratory experiments was conducted to test the occurence of the invasional meltdown phenomenon within the invasive Ponto-Caspian community. Preferences of an alien Ponto-Caspian racer goby, Babka gymnotrachelus, towards amphipod preys of the same origin (Dikerogammarus villosus, Pontogammarus robustoides) or a prey species native to the resident community (Gammarus fossarum) were verified. Additionally, we tested the profitability of native and invasive prey for fish in a growth experiment. Accordingly with the invasional meltdown hypothesis, we hypothesized that the racer goby would prefer Ponto-Caspian amphipods and that prey would be more beneficial than native ones, which should result in higher growth rate. We found that the racer goby always selected the native G. fossarum, regardless of the prey mobility, presence of shelters and waterborne chemical cues. Thus, the fish choice was based on the assessment of prey quality during a direct contact with amphipods. The growth experiment indicated that the racer goby grew better on the native gammarid compared to the Ponto-Caspian species. The outcome of our study does not support the invasional meltdown hypothesis within the goby – gammarids predator prey system, as the non-native prey species were neither prefered nor more profitable food for the alien predator. Thus, we found no evidence for facilitation of establishement between the studied taxa

Some like it hot: factors impacting thermal preferences of two Ponto-Caspian amphipods Dikerogammarus villosus (Sovinsky, 1894) and Dikerogammarus haemobaphes (Eichwald, 1841)

Temperature is a crucial factor determining biology and ecology of poikilothermic animals. It often constitutes an important barrier for invasive species originating from different climate zones but, on the other hand, may facilitate the invasion process of animals with wide thermal preferences and high resistance to extreme temperatures. In our experimental study, we investigated the thermal behaviour of two Ponto-Caspian amphipod crustaceans—Dikerogammarus villosus and Dikerogammarus haemobaphes. Both species are known to live under a wide range of thermal conditions which may promote their invasion. Moreover, both these amphipods are hosts for microsporidian parasites which co-evolved with them within the Ponto-Caspian region and spread in European waters. As the presence of a parasite may influence the thermal preferences of its host, we expected to observe behavioural changes in infected individuals of the studied amphipods leading to (1) behavioural fever (selecting a warmer habitat) or (2) anapyrexia (selecting a colder habitat). The experiment (N = 20) was carried out for 30 min in a 100 cm. 20 cm from boths sides were not avaliable for amphipods long thermal gradient (0–40 °C), using 30 randomly selected adult amphipod individuals of one species. At the end of each trial, we checked the position of amphipods along the gradient and determined their sex and infection status (uninfected or infected by one of microsporidium species). D. villosus was infected with Cucumispora dikerogammari whereas D. haemobaphes was a host for C. dikerogammari, Dictyocoela muelleri or D. berillonum. Thermal preferences of amphipods depended on their species and sex. Females of D. villosus preferred warmer microhabitats (often much above 30 °C) than conspecific males and females of D. haemobaphes, whereas no significant differences were found among males of both species and both sexes of D. haemobaphes. Moreover, infected males of D. villosus stayed in warmer water more often than uninfected males of this species, selecting temperatures higher than 30 °C, which may be explained either as a behavioural fever constituting a defence mechanism of a host against the infection, or as a parasite manipulation of the host behaviour increasing the parasite fitness. On the other hand, none of the parasite species affected the thermal preferences of D. haemobaphes, including also C. dikerogammari, changing the behaviour of D. villosus. Our research presents the complexity of the thermal behaviour of studied amphipods and the evidence that microsporidia may trigger a change in temperature preferendum of their host species and those observations may be the result of different host-parasite coevolution time which may vary for the two host species (Poulin, 2010)

Første påvisning av Batrachochytrium dendrobatidis på Nordpadde i Norge

Taugbøl, A., Strand, D., Brandsegg, H., Bącela-Spychalska, K. & Baranowska, M. 2023. Første påvisning av Batrachochytrium dendrobatidis på Nordpadde i Norge. NINA Rapport 2255. Norsk institutt for naturforskning. http://hdl.handle.net/11250/3049762 Batrachochytrium dendrobatidis (Bd) er en algesopp i rekken Chytridiomycota, en av de mer primitive typene av sopp vi kjenner til i dag. Bd påfører amfibier infeksjonssykdommen chytridiomykose via zoo-sporer da amfibier fungerer som vertskap for Bd og blir bærere av zoosporangier. Selv om chytridiomykose hos amfibier nå har vært kjent i over tjue år og sykdommen har ført til drastisk reduksjon i flere amfibiepopulasjoner i enkelte verdensdeler, er det ennå relativt lite man vet om sykdomsforløpet til ulike arter av amfibier. Det er høy sannsynlighet at det er store mørketall på dødelighet da det foreligger få studier av dyrene i deres naturlige habitat igjennom sesongen. Det er tidligere påvist Bd på storsalamander (Triturus cristatus) i Norge, mens soppen trolig oppstod som vert på frosk og padde. Det ble derfor samlet inn totalt 70 prøver fra padde som ble testet for Bd i dette studiet. Totalt testet 32 individer positivt på Bd, fra fem ulike dammer (Tabell 1). Prevalensen av smittede dyr (antall smittede dyr/ totalt antall dyr testet) var mellom 40 (Vesletjernet) og 100% (Svartkulp og Froskedammen). Dette er første gang det er påvist Bd på padder i Norge. Alle de infiserte populasjonene ligger forholdsvis nært hverandre, og det er også påvist Bd fra ulike salamanderprøver i området (Taugbøl et al, upubliserte data). Det er uvisst hvordan Bd spres i terrenget, og flere nærliggende populasjoner bør prøvetas i nærmeste fremtid for å få en bedre oversikt over den faktiske geografiske utbredelsen. Det er tidligere tenkt at Bd er mer utbredt i urbane områder, mens resultater fra urbane områder i dette prosjektet er varierende med både Bd-frie og Bd-infiserte dammer i Urbane områder, er de to dammene som ble sjekket fra skogen (nær sti) infisert. Vi har per i dag undersøkt et meget begrenset geografisk område i Norge for smitte på padde, og det er begrenset kunnskap om konsekvenser av smitte i naturlige populasjoner. Fra forsøk i laboratorium på ulike froske- og paddearter er generelle funn at infiserte individer har lavere vekt, høyere metabolisme, lavere nivå av immunbeskyttende stoffer og mindre utviklede kjønnsorganer. Eksperimentelle undersøkelser viser også dødelighet opp mot 88% ved hibernering av infiserte individer. Dette tilsier at det sannsynligvis er mye «skjult» dødelighet ved for eksempel lavere overlevelse igjennom vinteren. Per i dag er det ingen overvåkning av paddepopulasjoner i Norge og det er derfor ikke mulig å utelukke negative arts- og populasjonseffekter av infeksjonen

Further steps of

Cryptorchestia garbinii Ruffo, Tarocco and Latella, 2014 (Amphipoda: Talitridae), a semiterrestrial amphipod, reported (as Orchestia cavimana Heller, 1865) from the Polish inland waters, e.g., the lowermost Vistula River, for the first time in 2009. Now, we have reported this species from the upper Oder River, which is c.a. 350 km SE from the closest known localities near Berlin, Germany. We confirmed its identity by the DNA barcodes and showed that all individuals found so far in other countries in Central and Western Europe represent the same haplotype, excluding a singleton from the locus typicus of this species in Lake Garda, Italy

Neogene paleogeography provides context for understanding the origin and spatial distribution of cryptic diversity in a widespread Balkan freshwater amphipod

Background The Balkans are a major worldwide biodiversity and endemism hotspot. Among the freshwater biota, amphipods are known for their high cryptic diversity. However, little is known about the temporal and paleogeographic aspects of their evolutionary history. We used paleogeography as a framework for understanding the onset of diversification in Gammarus roeselii: (1) we hypothesised that, given the high number of isolated waterbodies in the Balkans, the species is characterised by high level of cryptic diversity, even on a local scale; (2) the long geological history of the region might promote pre-Pleistocene divergence between lineages; (3) given that G. roeselii thrives both in lakes and rivers, its evolutionary history could be linked to the Balkan Neogene paleolake system; (4) we inspected whether the Pleistocene decline of hydrological networks could have any impact on the diversification of G. roeselii. Material and Methods DNA was extracted from 177 individuals collected from 26 sites all over Balkans. All individuals were amplified for ca. 650 bp long fragment of the mtDNA cytochrome oxidase subunit I (COI). After defining molecular operational taxonomic units (MOTU) based on COI, 50 individuals were amplified for ca. 900 bp long fragment of the nuclear 28S rDNA. Molecular diversity, divergence, differentiation and historical demography based on COI sequences were estimated for each MOTU. The relative frequency, geographic distribution and molecular divergence between COI haplotypes were presented as a median-joining network. COI was used also to reconstruct time-calibrated phylogeny with Bayesian inference. Probabilities of ancestors’ occurrence in riverine or lacustrine habitats, as well their possible geographic locations, were estimated with the Bayesian method. A Neighbour Joining tree was constructed to illustrate the phylogenetic relationships between 28S rDNA haplotypes. Results We revealed that G. roeselii includes at least 13 cryptic species or molecular operational taxonomic units (MOTUs), mostly of Miocene origin. A substantial Pleistocene diversification within-MOTUs was observed in several cases. We evidenced secondary contacts between very divergent MOTUs and introgression of nDNA. The Miocene ancestors could live in either lacustrine or riverine habitats yet their presumed geographic localisations overlapped with those of the Neogene lakes. Several extant riverine populations had Pleistocene lacustrine ancestors. Discussion Neogene divergence of lineages resulting in substantial cryptic diversity may be a common phenomenon in extant freshwater benthic crustaceans occupying areas that were not glaciated during the Pleistocene. Evolution of G. roeselii could be associated with gradual deterioration of the paleolakes. The within-MOTU diversification might be driven by fragmentation of river systems during the Pleistocene. Extant ancient lakes could serve as local microrefugia during that time

The killer shrimp, Dikerogammarus villosus, invading European Alpine lakes: a single main source but independent founder events with an overall loss of genetic diversity.

16 pagesInternational audience1. The effects of biological invasions are generally more detrimental in isolated ecosystems than in the interconnected ones and freshwater lakes appear to be particularly fragile. The Ponto-Caspian freshwater amphipod Dikerogammarus villosus (Pontogammaridae), also known as the killer shrimp, is a highly invasive species that can have significant ecological impacts on receiving ecosystems. It has colonised most of the European main inland waterbodies, including at least 12 lakes in the Alps – an area of high conservational priority and, at the same time, heavily affected by anthropogenic changes. Particularly, overland translocations of boats among tourist centres may have contributed to colonisation of Alpine lakes by D. villosus.2. We aimed to answer the following questions: Which of the two genetically differentiated populations invading continental lowland Europe has contributed to colonisation of the Alpine lakes? Is it possible to detect independent founder events in different regions of the Alps and/or secondary spread among European Alpine lakes? Have the lacustrine populations suffered any reduction in genetic variation during colonisation? Twelve populations from the Alpine lakes were genotyped for a portion of mtDNA (COI and 16S) and for seven nuclear microsatellite loci. A wide range of methods was used to analyse the data, including haplotype network, Bayesian clustering and demography tests.3. Our results show that the lowland western route (Danube-Rhine waterway) of the killer shrimp invasion was the source for introduction to European Alpine lakes. Unlike invasive populations in the main lowland rivers, most of the Alpine populations suffered bottleneck and had significantly lower genetic diversity compared to their source population along the western route. We found clear patterns of genetic structure, revealing multiple independent lake colonisations followed by secondary spread between lakes. An overland transport of D. villosus with tourist boats is probably the major spreading vector to and among Alpine lakes. Implementing safety programmes such as the ‘check, clean, and dry’ procedures may stop or slow down spreading of D. villosus among the Alpine lakes, and prevent additional long distance transport

Cryptic diversity and mtDNA phylogeography of the invasive demon shrimp, Dikerogammarus haemobaphes (Eichwald, 1841), in Europe.

34 pagesInternational audienceThe regions of the Black, Caspian, and Azov seas are known for being both (i) the place of extensive crustacean radiation dated to the times of Paratethys and Sarmatian basins, and (ii) present donors of alien and invasive taxa to many areas worldwide. One amphipod morphospecies, Dikerogammarus haemobaphes, is known both as native to rivers draining to the Black and Caspian seas as well as a successful invader (nicknamed demon shrimp) in Central and Western European rivers. Based on mitochondrial (COI and 16S) and nuclear (28S) datasets and 41 sampling sites, representing both the native (19) and the invaded (22) range, we assessed cryptic diversity, phylogeography and population genetics of this taxon. First, we revealed the presence of two divergent lineages supported by all markers and all species delimitation methods. The divergence between the lineages was high (18.3% Kimura 2-parameter distance for COI) and old (ca. 5.1 Ma), suggesting the presence of two cryptic species within D. haemobaphes. Lineage A was found only in a few localities in the native range, while lineage B was widespread both in the native and in the invaded range. Although genetic divergence within lineage B was shallow, geographic distribution of 16S and COI haplotypes was highly heterogeneous, leading us to the definition of four Geo-Demographic Units (GDUs). Two GDUs were restricted to the native range: GDU-B1 was endemic for the Durugöl (aka Duruşu) Liman in Turkey, whereas GDU-B2 occurred only in the Dniester River. GDU-B3 was both present in several localities in the native range in the Black Sea drainage area and widespread in Central and Western Europe. The GDU-B4 was found exclusively in the Moskva River in Russia. Extended Bayesian Skyline Plot indicated steady growth of GDU-B3 population size since 30 ka, pointing to the rather old history of its expansion, first in the late Pleistocene in the native range and nowadays in Central and Western Europe. The analysis of haplotype distribution across the present distribution range clearly showed two invasion routes to Central and Western Europe. The first one, originating from the lower Dnieper, allowed the demon shrimp to colonize Polish rivers and the Mittellandkanal in Germany. The second one, originating from the Danube delta, allowed to colonize the water bodies in the upper Danube basin. The UK population has originated from the Central Corridor, as only a haplotype found exclusively along this route was recorded in the UK. Population genetics analysis showed that the invasion of the demon shrimp along the Central Corridor was not associated with the loss of genetic diversity, which might contribute to the success of this invader in the newly colonized areas

Zebra mussel beds: an effective feeding ground for Ponto-Caspian gobies or suitable shelter for their prey?

Aggregations of the Ponto-Caspian invasive zebra mussel (Dreissena polymorpha) constitute a suitable habitat for macroinvertebrates, considerably increasing their abundance and providing effective antipredator protection. Thus, the overall effect of a mussel bed on particular predator species may vary from positive to negative, depending on both prey density increase and predator ability to prey in a structurally complex habitat. Alien Ponto-Caspian goby fish are likely to be facilitated when introduced into new areas by zebra mussels, provided that they are capable of utilizing mussel beds as habitat and feeding grounds. We ran laboratory experiments to find which prey (chironomid larvae) densities (from ca. 500 to 2,000 individuals m−2) in a mussel bed make it a more beneficial feeding ground for the racer goby Babka gymnotrachelus (RG) and western tubenose goby Proterorhinus semilunaris (WTG) compared to sandy and stone substrata (containing the basic prey density of 500 ind. m−2). Moreover, we checked how food availability affects habitat selection by fish. Mussel beds became more suitable for fish than alternative mineral substrata when food abundance was at least two times higher (1,000 vs. 500 ind. m−2), regardless of fish size and species. WTG was associated with mussel beds regardless of its size and prey density, whereas RG switched to this habitat when it became a better feeding ground than alternative substrata. Larger RG exhibited a stronger affinity for mussels than small individuals. WTG fed more efficiently from a mussel bed at high food abundances than RG. A literature review has shown that increasing chironomid density, which in our study was sufficient to make a mussel habitat an attractive feeding ground for the gobies, is commonly observed in mussel beds in the field. Therefore, we conclude that zebra mussels may positively affect the alien goby species and are likely to facilitate their establishment in novel areas, contributing to an invasional meltdown in the Ponto-Caspian invasive community