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Phenotypic differentiation of Round goby (Neogobius melanostomus) along small-scale invasion succession
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.ORCID iD: 0000-0002-5050-2880
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
(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 [en]
round goby, Neogobius melanostomus, behavioural traits, phenotype, species invasions, lag-phase, spread
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-111907OAI: oai:DiVA.org:umu-111907DiVA: diva2:873976
Available from: 2015-11-25 Created: 2015-11-25 Last updated: 2015-11-26
In thesis
1. Round goby invasion of the Baltic Sea: the role of phenotypic variation
Open this publication in new window or tab >>Round goby invasion of the Baltic Sea: the role of phenotypic variation
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
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:nbn:se:umu:diva-111910 (URN)978-91-7601-328-1 (ISBN)
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

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Thorlacius, Magnus
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Department of Ecology and Environmental Sciences
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