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  1. Jane W Behrens
  2. April Blakeslee
  3. Steve Bourne
  4. Isabel Casties
  5. Pierre Charrier (poster)
  6. Ellika Faust (presentation)
  7. Ellika Faust (poster)
  8. Elisabet Forsgren (poster)
  9. Kimberly Gilbert
  10. Leon Green
  11. Jonne Kotta
  12. Halvor Knutsen
  13. Erika Leder
  14. Kiran Liversage
  15. Helen Nilsson Sköld
  16. Henrik Pavia
  17. Jörgen Ripa
  18. Marc Rius
  19. Rick Shine
  20. Ola Svensson (poster)
  21. Filip Volckaert

Dispersal potential of the invasive round goby – how plastic are they? 

Jane W Behrens

Originating from the Ponto-Caspian region, the round goby has proven a successful invader in the Baltic Sea, several European rivers and the North American Great Lakes. It thus thrives in fresh and brackish waters, yet still no oceanic populations exist. We have investigated the species physiological capacity for dispersal into a fully marine environment. Furthermore, assuming that the invasion front is led by bold individuals, we have put forward the hypothesis’ that bold fish are better at camouflaging themselves, and are superior competitors for food as compared to shy conspecifics. Preliminary results from experiments testing these hypotheses will be presented.

NW Atlantic population structure and gene flow in the European Green Crab: an update on its dynamic invasion front and future implications

April Blakeslee

The green crab (Carcinus maenas) is one of the most notorious marine invaders globally—established on nearly every continent but native to just one. In the NW Atlantic, C. maenas has had two major introduction events. The first invasion (1800s) introduced western European genotypes to the mid-Atlantic USA that expanded northeast, reaching southwest Atlantic Canada ~100 years later but stalling around Halifax in 1960-70s. The second cryptic invasion (1980-90s) introduced novel northern European genotypes to eastern Atlantic Canada, which have spread in the region, especially southwest with the mean flow of currents. Not only did this latter invasion lessen the crab’s genetic bottleneck, but it also led to admixture of genotypes from the two introduction events in Atlantic Canada. Several of those admixed genotypes were recently transported to Newfoundland, likely via ballast water originating near Halifax. This talk updates the current understanding of this highly dynamic system, adding genetic data from 2013-2015 to the 15 year dataset. We find that the invasion front of admixed genotypes has continued to expand in the region both to the southwest and to the northeast. Also, the novel northern genotypes have increased in frequency in western Atlantic Canada and northeast USA as predicted by population models. Continued monitoring is important for better understanding the crab’s overall impact in the region and the possible phenotypic consequences of this ongoing admixture and spread.

Reconstructing invasion routes of species with different introduction periods using genomic data

Steve Bourne

The role of geographic origin for invasion success

Isabel Casties

Several studies have indicated that species from the Ponto-Caspian region may be evolutionary predisposed to become non-indigenous species (NIS). If species from certain areas 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 more effective strategy than eradication or control of established NIS populations. We compared observed numbers of established NIS in the North and Baltic Seas and Great Lakes-St. Lawrence River 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. Ponto-Caspian taxa colonized both types of habitats, saltwater and freshwater areas, in much higher numbers than expected. Propagule pressure (i.e. number of introduced individuals) is of great importance for establishment success of NIS; however in our study neither shipping vector nor environmental match between regions clarified the high numbers of Ponto-Caspian taxa in the two areas. Although we cannot exclude the influence of other transport vectors, our findings suggest that the origin of species plays an important role for the predisposition of successful invaders.

Transcriptomic studies uncover the hard tick phylogeny, poster

N. Pierre Charrier, Axelle Hermouet, Caroline Hervet, Olivier Lambert, Albert Agoulon, Stephen Barker, Dieter Heylen, Olivier Plantard, Claude Rispe

Keywords : Phylogeny, Phylogenomics, RNA-Seq, Multispecific transcriptome reconstruction, Ixodes, Ticks

Hard ticks are vectors of numerous pathogens responsible for human and veterinary diseases. The Ixodes genus is distributed world-wide and comprises several species that transmit the Lyme borreliosis agent (Borellia sp.). To better understand evolutionary patterns in this genus (for example how adaptations to different host species or host ranges evolved, and how fast did they change over evolutionary time), an accurate phylogeny of the whole group is needed. Yet, the phylogeny of the group was not completely resolved until recently. Points debated are for example the phylogenetic position of Australasian species (e.g. I. uriae, I. holocyclus), or at a very fine scale, the phylogenetic relationships between closely related species (e.g. in the I. ricinus / I. scapularis group).

Using high output sequencing technology (RNA-Seq), we investigated phylogenetic relationships in the group of hard ticks. Transcriptomes from 9 species in the Ixodes genus were sequenced using Illumina strand-oriented, paired-end sequencing. The new data set produced by our group was combined whith data obtained from Genbank for two other Ixodes species as well as 10 non-Ixodes tick species. We obtained de novo transcriptome assemblies for each species (21 in total), predicted their coding sequences and performed sequence comparisons among species. Single copy orthologs (SCO) were aligned. Maximum-likelihood and Bayesian framework were used to reconstruct the species tree. We aim to provide thereby new insights on the evolutionary history of ticks, producing a solid framework for further analyses of phylogeny and gene evolutionary patterns.

Fish colonisation: human mediated transfer or natural range expansion? (presentation)

Ellika Faust

Farmed fish escaping aquaculture is a known, and highly debated issue. However, non-target species, such as cleaner fish which are used to remove sea lice from the targeted farmed fish, are rarely taken in consideration. Wild wrasses are caught and transported long distances to be used as cleaner fish in salmon farms without considering genetic or other effects on local wrasse populations. We investigate the origin of wild Corkwing wrasse at the northern edge of its distribution range in mid Norway, amidst Salmon farms which heavily relies on long distance import of wrasse cleaner fish from the coast of Skagerrak and Kattegat. Using SNPs identified with 2bRAD sequencing, we assessed genetic differentiation among Corkwing wrasse collected in mid Norway, two locations in western Norway and three southern locations on the coast of Skagerrak and Kattegat. The mid population appears to mainly be a result of a northwards expansions, but showed considerable gene flow from Skagerrak and Kattegat, indicating escape of wrasses from aquaculture. Out of 40 fish, we detected two individuals with clear southern genotypes, one first generation hybrid and fourteen potential second generation hybrids. We provide evidence of Corkwing wrasse escaping from farms to the wild, and hybridization with local populations; the magnitude and significance of this impact warrants further investigation.

Origin and route of establishment of the invasive Pacific oyster Crassostrea gigas in Scandinavia. (poster)

Ellika Faust

Identifying the routes and rates of introductions is fundamental for the understanding of marine invasions. Recurring introductions over the last 50 yr have led to the establishment of feral Pacific oyster Crassostrea gigas populations throughout Europe. In the northern countries, Sweden and Norway, the species first occurred in large numbers in 2006. Here, we investigated the relative importance of introduction via re-laying of cultured oysters imported for consumption from France, Ireland or the Netherlands, and dispersal of oyster larvae by ocean currents from wild oyster populations in Denmark. Using microsatellite DNA markers, we estimated genetic differentiation among Pacific oysters collected at 4 Swedish locations, 3 Norwegian locations and 9 potential source locations in Denmark, Ireland, the Netherlands and France. All Swedish samples and 1 Norwegian sample (Tromlingene) were genetically similar to each other and the Danish samples and showed significant genetic differentiation from all other populations. Consequently, it appears that the Pacific oyster populations in Sweden, Denmark and Tromlingene are closely connected and/or share a recent origin. The 2 remaining Norwegian samples (Hui and Espevik) differed from each other and all other populations, but showed similarities to wild oyster samples from Scandinavia and Ireland, respectively. Overall, the results underline a complex origin of Norwegian oysters, with gene flow from Swedish/Danish populations, as well as other unidentified sources. The apparent connectivity among most of the Scandinavian populations has implications for regional management of this invasive species, and highlights possible scenarios for other marine invasive species with a similar life history.

Dispersal pathways of alien species in Norway, including the Arctic (Svalbard)

Elisabet Forsgren & Ditte Hendrichsen, Norwegian Institute for Nature Research, Trondheim

Once alien species have established in new regions, it is often very difficult to completely remove them, and the costs of removal is generally much higher than preventing their establishment in the first place. Knowledge about dispersal pathways and vectors are therefore central to effective prevention of immigration, spread and establishment of alien species.
We analyzed the pathways of 1170 alien species that reproduce in mainland Norway and 1071 alien species that are here but without reproducing populations, as well as 79 species from Svalbard. (Data from the Norwegian Biodiversity Information Centre.)
The number of introduced alien species to Norway have increased dramatically over the past 100 years. There is a clear positive correlation between the development in wealth, measured as gross development product, population growth and import of goods, and the number of new species arriving in Norway each year. Most alien species have established in Norway as a result of naturalization, followed by species that have come to the country as a stowaway. This is in contrast to the non-reproductive alien species, where stowaway is by far the most important dispersal pathway. Both groups are dominated by vascular plants. Marine species have primarily come by escape from captivity or as stowaway. Different dispersal pathways were found to be differently associated with the probability of establishment and ecological risk. We also analysed whether certain species traits was associated with dispersal pathway and ecological risk. The aims of a new project focusing on dispersal pathways in the Arctic (Svalbard) are also presented.

Recovery from expansion load is limited during species range shifts

Kimberly Gilbert

Populations undergoing spatial range expansions are subject to gene surfing, which is known to contribute to maladaptive expansion load. During a standard range expansion, populations at the expanding front are subject to reduced efficacy of selection due to small effective population size and experience repeated founder events as they continue to colonize new habitat. The surfing of deleterious variants that this demographic process creates can lead to significant reductions in fitness. However, after an expansion and once population size recovers, migration from the core of a species range combined with more efficient selection at the recent edge both lead to recovery from expansion load. We investigate an equally likely demographic process, termed a range shift, where an expanding front occurs ahead of a receding trailing edge. We hypothesize that these shifts are more common for specialist species that must track specific environments over space as climate or other environmental conditions change. As this constant-width population moves over space, expansion load accumulates at the front, and the extinction at the trailing edge eliminates beneficial diversity that would persist in a standard range expansion. Through simulation, we show that this demographic process can lead to further fitness reductions than a standard range expansion, and furthermore may prevent recovery and leave populations in a state of reduced fitness and thus more prone to extinction from any stochastic forces that may threaten their long-term persistence.


Is there 'phenotypic sorting' of round goby in the salinity gradient of the Gothenburg harbor? – findings for the future colonization.

Leon Green


The round goby, Neogobius melanostomus, is the north European poster boy for aquatic invasions. It is tolerant of a wide range of environmental conditions, including temperature, oxygen and salinity. Though tolerant, these conditions can be adverse enough to cause selection and potentially create different ‘ecotypes’. There is for example a lot of evidence of round goby from freshwater and brackish water being quite different. If they are of different origin and adapted to different conditions, one can expect them to seek out these optimal conditions when transferred to a new location. If the individuals with the most optimal traits for surviving and reproducing in higher salinity seek out these conditions, it likely has consequences for the spread of the species. In our study, we assess this ‘phenotypic sorting’ by looking at phenotypic traits across different localities in the salinity gradient of Gothenburg harbor on the Swedish west coast. In this talk results from the study are presented, and the consequences for the spread of the species into the North Sea coastline is discussed.

Novel ecological function causes marine ecosystem regime shift: the Baltic Sea perspective

Jonne Kotta

Long-term monitoring reveals stable coexistence of genetically divergent Atlantic cod ecotypes in coastal waters

Halvor Knutsen

Do genetic origin have a significant ecological relevance in preventing homogenization in marine populations? We show a stable coexistence of two main genetically divergent Atlantic cod ecotypes in coastal waters, were the coastal ecotype dominated in sheltered waters and the offshore ecotype dominated in exposed waters, although both ecotypes where present in all levels of exposure. Interestingly, we find that individuals of offshore origin are larger in size despite being the same age (number of days) than those of coastal origin in all habitats, levels of exposure and all regions along the coast due to faster growth, suggesting that genetic origin have a significant ecological relevance, preventing homogenization.

Genomic approaches to understanding local adaptation in the sand goby

Erica Leder

The distribution of animals is not only determined by which environment adults can tolerate, but in which environment they can reproduce. Based on experiments on the sand goby, Pomatoschistus minutus, aimed at understanding local adaptation of reproductive traits, we found that males have difficulties to reproduce outside their native salinity. Gametes may play a significant role in salinity adaptation, since sperm from seems to perform poorly in non-native salinity. To further investigate the genomic mechanisms of adaptation to salinity, we sequenced the genome of the sand goby, conducted transcriptomic and proteomic studies of testes tissue as well as performed a genome-wide SNP outlier analysis comparing populations with different salinities. Preliminary results of the genome assembly, outlier analysis and gene expression analysis will be presented.

The interaction of native perch and invasive round goby involves characteristics of physical environment and macrophyte habitat

Kiran Liversage, Kristiina Nurkse, Jonne Kotta
Estonian Marine Institute, University of Tartu, Tallinn, Estonia

The Baltic Sea is impacted by multiple stressors with invasive species currently being responsible for a major reorganization of its coastal ecosystems. Here we model how the novel epibenthic predator, round goby (Neogobius melanostomus), has been incorporated into diets of native perch (Perca fluviatilis). Analyses of stomach content showed that round goby comprised a large proportion of all prey items. Predation pressure appeared to increase with elevated water temperature and visibility. The round goby is mostly preyed on by 15−30cm sized perch but other size-classes may also consume large amounts of the novel fish. Macrophytes provide a refuge from predation for the round goby, and in areas with over 60% macroalgae coverage, the round goby was practically not consumed. Surprisingly, the density of round goby only marginally affected the feeding of perch. Overall, the round goby is well incorporated into the coastal food webs of the Baltic Sea and provides a significant source of nutrient for native predatory fish. A lack of density-dependence in the perch-goby interaction suggests that the numbers of round goby are far beyond control by predators, and perch have little role in controlling the density of round goby in Baltic Sea coastal ecosystems.

Colour change in fish

Helen Sköld
Havets Hus i Lysekil

Phenotypic plasticity allows persistence despite a changing environment. In fish and other lower animals, the ability to change skin color is one such trait that is used for both camouflage and signaling. In this presentation, I present the latest results from the work on regulation of color change in fish from me and my collaborators. I finally discuss how flexible camouflage by means of colour change may facilitate successful invasion of alien species into novel habitats.

Henrik Pavia

Range shifts in a changing climate - a review of current theories, and some new results.

Jörgen Ripa

The response of natural systems to a changing climate is an hot topic, it has an applied side but also a basic science side. A central question is whether species will adapt to new conditions or simply track the climate, i.e. shift their ranges. Range shifts may cause severe costs to agriculture or forest management. At the same time, the possibility of a range shift may be the only way for a species to survive in the long term. Range shifts are thus also of a large conservation interest. Many new ideas and theories are currently emerging on this topic. Here I summarize a few of them, and present some new results regarding the ability of species to track a shifting climate when competitors are ’in the way’.

Ecological and evolutionary consequences of the global redistribution of biodiversity

Marci Rius

An evolutionary perspective on biological invasions

Rick Shine


Invasion is an evolutionary as well as ecological process. Both the invader and the recipient ecosystem are suddenly confronted by novel challenges. An invasion unleashes powerful new evolutionary forces, some of them the ones we are familiar with (such as natural selection) but others that are novel, and only seen in spatially non-equilibrial systems (such as spatial sorting and mutation surfing). I will review information from our studies on the cane toad invasion of tropical Australia, to ask how an evolutionary perspective can inform our understanding, and how we can use those insights to frame more effective approaches for invader control and mitigation of impact.

Immigrant reproductive dysfunction facilitates ecological speciation (poster)

Ola Svensson, Johanna Gräns, Malin C. Celander, Jonathan Havenhand, Erica H. Leder, kai Lindström, Sofie Schöld, Cock van Oosterhut, Charlotta Kvarnemo

The distributions of species are not only determined by where they can survive – they must also be able to reproduce. Although immigrant inviability is a well-established concept, the fact that immigrants also need to be able to effectively reproduce in foreign environments has not been fully appreciated in the study of adaptive divergence and speciation. Fertilization and reproduction are sensitive life-history stages that could be detrimentally affected for immigrants in non-native habitats. We propose that “immigrant reproductive dysfunction” is a hitherto overlooked aspect of reproductive isolation caused by natural selection on immigrants. This idea is supported by results from experiments on an externally fertilizing fish (sand goby, Pomatoschistus minutus). Growth and condition of adults were not affected by non-native salinity whereas males spawning as immigrants had lower sperm motility and hatching success than residents. We interpret these results as evidence for local adaptation or acclimation of sperm, and possibly also components of paternal care. The resulting loss in fitness, which we call “immigrant reproductive dysfunction,” has the potential to reduce gene flow between populations with locally adapted reproduction, and it may play a role in species distributions and speciation.

Parasite introduction with an invasive goby in Belgium: double trouble?

Filip Volckaert

Page Manager: Eva Marie Rödström|Last update: 10/5/2017

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