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Round goby invasion of the Baltic Sea: the role of phenotypic variation
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0002-5050-2880
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Biological invasions are a major threat to biodiversity world wide with annual economic costs up to 1.4 trillion dollars. The round goby (Neogobius melanostomus) is a particularly fierce invader that threatens ecological function of the Baltic Sea. Individual variation in behavioral traits that remain constant through time and context have been identified as crucial factors for explaining different parts of the invasion process. For example, asocial behavior facilitates dispersal from high density populations and comes with fitness benefits in low conspecific density. The latter is especially relevant, in an invasion context, following the initial colonization of a novel environment when population density usually is low.

This thesis investigates the role of individual variation in phenotypic traits on species invasions. The main focus is on the effects of sociability, activity and boldness, but also including aggression and physiological stress tolerance, on dispersal tendency and selection at invasion fronts. To do this, we studied four round goby populations in the Baltic Sea, two of the most recently established and two of the oldest populations.

In 2012 we demonstrated that asocial, active and bold round gobies are overrepresented at invasion fronts. Two years later we showed that dispersal from the new populations was led by individuals with high activity levels, while in all populations larger individuals dispersed. We also determined the length of the socalled lag-phase, between colonization and spread, in both newly established populations. The end of the lag-phase is hypothesized being triggered by high population density in the harbors leading to dispersal and subsequen colonization of the surrounding areas by small asocial individuals. In our final experiment, we present evidence of stress coping styles in round gobies, in which more aggressive individuals are also more stress tolerant and vice versa. Though we found no connection between stress coping and population age, we found that mortality was unaffected by population density and that the gobies became more aggressive and stress tolerant when kept in high density.

To conclude, we have shown that: 1) individuals with high levels of activity, boldness and asociality are common at invasion fronts; 2) a lag phase occurs between colonization and spread in round goby invasions; 3) asocial individuals drive the spread from high density populations at the invasion front and; 4) round gobies adapt to high densities with high aggression and stress tolerance. 

Place, publisher, year, edition, pages
Umeå: Umeå University , 2015. , 40 p.
Keyword [en]
Round goby (Neogobius melanostomus), behaviour, animal personality, dispersal, species invasions, colonisation, spread, sociability, activity, boldness, aggression, cortisol coping-styles
National Category
Ecology
Research subject
biology
Identifiers
URN: urn:nbn:se:umu:diva-111910ISBN: 978-91-7601-328-1 (print)OAI: oai:DiVA.org:umu-111910DiVA: diva2:874022
Public defence
2015-12-18, KB3B1, Linnaeus väg 6, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-11-27 Created: 2015-11-25 Last updated: 2015-11-26Bibliographically approved
List of papers
1. Personality differentiation along the invasion succession of the round goby (Neogobius melanostomus) in the Baltic Sea
Open this publication in new window or tab >>Personality differentiation along the invasion succession of the round goby (Neogobius melanostomus) in the Baltic Sea
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Biological invasions, or the movement of species beyond their native range to settle and breed in novel environments, are an ever-growing problem in many parts of the world. A particularly successful invader is the round goby (Neogobius melanostomus), a benthic fish from the Ponto-Caspian region that invaded both the Baltic Sea and the Laurentian Great Lakes in 1990 and has since spread throughout most of Europe’s river systems and into rivers surrounding the Great Lakes. During the past decade, evidence has gathered for the importance of animal personality, or individual specific behavioral traits that display limited plasticity, in the invasion process. Individuals that disperse have been found less social, bolder, more active and to have a greater tendency to explore novel environments. With this study we are

the first to show that round gobies from newly established populations (~4 years) are less social, bolder and more active than those from populations that are older in the invasion succession (>20 years), thereby showing that individuals in newly established populations are not a random sample from the source population. Additionally, all behaviors were correlated indicating a behavioral syndrome in which behavioral adaptation for dispersal (less social, bolder and more active) is dominant in newly established populations. 

Keyword
personality, behavioural syndromes, dispersal, round goby, Neogobius melanostomus, invasive fish, benthic fish
National Category
Ecology
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-111906 (URN)
Available from: 2015-11-25 Created: 2015-11-25 Last updated: 2015-11-26
2. Behavioral dependent dispersal in the invasive round goby Neogobius melanostomus depends on population age
Open this publication in new window or tab >>Behavioral dependent dispersal in the invasive round goby Neogobius melanostomus depends on population age
2015 (English)In: Current Zoology, ISSN 1674-5507, Vol. 61, no 3, 529-542 p.Article in journal (Refereed) Published
Abstract [en]

Biological invasions cause major ecological and economic costs in invaded habitats. The round goby Neogobius melanostomus is a successful invasive species and a major threat to the biodiversity and ecological function of the Baltic Sea. It is native to the Ponto-Caspian region and has, via ballast water transport of ships, invaded the Gulf of Gdansk in Poland. Since 1990, it has spread as far north as Raahe in Northern Finland (64 degrees 41'04"N, 24 degrees 28'44"E). Over the past decade, consistent individual differences of behavioral expressions have been shown to explain various ecological processes such as dispersal, survival or reproduction. We have previously shown that new and old populations differ in personality trait expression. Individuals in new populations are bolder, less sociable and more active than in old populations. Here we investigate if the behavioral differentiation can be explained by phenotype-dependent dispersal. This was investigated by measuring activity, boldness and sociability of individually marked gobies, and subsequently allowing them to disperse in a system composed of five consecutive tanks connected by tubes. Individual dispersal tendency and distance was measured. Our results revealed that in newly established populations, more active individuals disperse sooner and that latency of a group to disperse depends on the mean sociability of the group. This indicates the presence of personality dependent dispersal in this species and that it is maintained at the invasion front but lost as the populations get older.

Keyword
Personality, Activity, Dispersal, Round goby, Neogobius melanostomus, Species invasions
National Category
Zoology
Identifiers
urn:nbn:se:umu:diva-106570 (URN)000356968400015 ()
Available from: 2015-07-20 Created: 2015-07-20 Last updated: 2017-12-04Bibliographically approved
3. Phenotypic differentiation of Round goby (Neogobius melanostomus) along small-scale invasion succession
Open this publication in new window or tab >>Phenotypic differentiation of Round goby (Neogobius melanostomus) along small-scale invasion succession
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Species invasions are an ever-growing problem that increases with globalization through increased frequency of unintentional introductions. Between establishment and spread, a lag phase often occurs in which population growth is exponential and dispersal frequency low. Individual variation in behavioral traits, consistent through time and context, have been found crucial for understanding ecological processes such as density dependent dispersal during species invasions. In a previous study of the invasive round goby (Neogobius melanostomus), we found population differentiation between old and new populations in the Baltic Sea with individuals in new populations being more asocial, bold and active. Here we investigate if behavioral differentiations are created already during the initial spread from newly established populations. Hence, we monitored population growth and subsequent small-scale spread (< 800 m) in two newly

invaded areas, as well as the behavioral traits priory connected to dispersal, over two successional seasons. We found phenotypic differentiation between dispersing and resident individuals with small-scale dispersers being smaller and more asocial. In addition, our catch- per-unit-effort data suggest a lag-phase of 3-5 years, following initial colonization, before the round goby start spreading into the surrounding environment. This suggests that, at least in species that grow to high densities fast, sociability is more important than boldness and activity for triggering density-dependent dispersal. 

Keyword
round goby, Neogobius melanostomus, behavioural traits, phenotype, species invasions, lag-phase, spread
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-111907 (URN)
Available from: 2015-11-25 Created: 2015-11-25 Last updated: 2015-11-26
4. Stress coping styles in response to high densities in invasive populations of the round goby (Neogobius melanostomus) in the Baltic Sea
Open this publication in new window or tab >>Stress coping styles in response to high densities in invasive populations of the round goby (Neogobius melanostomus) in the Baltic Sea
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Over the past decade, individual differences in behavior have gained much interest in the context of species invasions. Certain behavioral traits, such as e.g. aggression, have been suggested to facilitate invasion success and a number of studies have found founding populations at invasion fronts to be a non-random sample of behavioral types from their source populations. In many animals, behavioral and physiological responses to challenge are connected, forming stress coping styles. However, there is a lack of studies considering the role of physiological stress response or coping styles during species invasions. Therefore we investigated the connection between aggression and stress response to high densities, in four invasive round goby (Neogobius melanostomus) populations of different age. We found the

first evidence for stress coping styles in round gobies, as individuals with a low stress response to high densities are also more aggressive. We did not find an effect of population age, likely because the youngest populations used were already too old, meaning that traits selected for at invasion fronts had started to fade out. Given that individual levels of aggression and stress tolerance are dependent on one another, and aggression has previously been identified as an important facilitator of dispersal and invasion success, stress coping styles should be an important factor during species invasions. 

Keyword
round goby, Neogobius melanostomus, aggression, plasma cortisol, species invasions, stress-tolerance
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-111909 (URN)
Available from: 2015-11-25 Created: 2015-11-25 Last updated: 2015-11-26

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