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Variation in number of vertebrae in populations of pike (Esox lucius) in the south-east of Sweden
Linnaeus University, Faculty of Health and Life Sciences, Department of Biology and Environmental Science.
2016 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [sv]

Antalet ryggkotor varierar kraftigt mellan olika taxa, men också inom arter eller populationer. Omfattande forskning har visat att antalet ryggkotor hos fisk är resultatet av interaktioner mellan genetisk struktur och plastiska svar på miljöbetingelser under individens ontogeni. Ett vanligt mönster är tendensen för antalet ryggkotor att variera med kroppsform och/eller kroppslängd hos fisken. Gäddan (Esox lucius) i Östersjön har en komplex populationsstruktur, bestående av flera genetiskt distinkta subpopulationer, vilka utgörs av anadroma individer som uppvisar ett homing-beteende. Individer som tillhör dessa subpopulationer är sympatriska större delen av året och blir allopatriska endast kortvarigt under tiden för lek. Den här studien undersökte fördelningen av antalet ryggkotor hos tre anadroma sympatriska subpopulationer av gädda iÖstersjön. Signifikanta skillnader i fördelningen av antalet ryggkotor hittades både inom och mellan alla undersökta subpopulationer och åldersklasser. Resultaten från ett ”common-garden” experiment antydde att skillnader i antalet ryggkotor mellan olika subpopulationer delvis hade en genetisk basis, vilket indikerar möjligheten för selektion att verka på denna egenskap, och en potentiellt evolutionär förändring. En kvadratisk regression visade på ett kurvilinjärt samband mellan antalet ryggkotor och kroppslängd hos juveniler. Tillsammans tyfrt dessa resultat på att de kombinerade effekterna av stabiliserande och divergent selektion kan ha spelat en roll i fördelningen av antalet ryggkotor hos gäddan i Östersjön. Fördelningen av antalet ryggkotor inom subpopulationer verkar vara under inflytande av stabiliserande selektion. Skillnader mellan subpopulationer kan istället reflektera lokala anpassningar som drivs av divergent selektion. Dessa fynd signalerar behovet av att betrakta varje subpopulation som en egen enhet i bevarandebiologiska sammanhang.

Abstract [en]

Vertebral number (VN) is known to vary greatly across different taxa, but also within species orpopulations. Extensive research has shown that VN in fish is the result of interactions between geneticstructure and plastic responses to environmental cues during ontogeny. A frequently reported pattern is the tendency for VN to vary with body shape and/or length of the fish. The pike (Esox lucius) of the Baltic Sea has a complex population structure, with genetically distinct subpopulations consisting of homing anadromous individuals. Individuals belonging to these subpopulations are sympatric for most of their lives and become allopatric briefly during spawning each year. This study examined the distribution of VN in three anadromous sympatric subpopulations of pike in the Baltic. Significant differences in VN were found between juveniles and adults belonging to different subpopulations, but also across life-stageswithin all three subpopulations. Results from a common-garden experiment indicated that differences in VN among subpopulations were in part the result of genetic differences, indicative of evolutionary change. Furthermore, a quadratic regression revealed a curvilinear relationship between VN and bodylength of juveniles. Taken together, these results suggest that the combined effects of stabilizing and divergent selection might have played a role in shaping the distribution of VN in pike of the Baltic. The distribution of VN within subpopulations seems to be under the influence of stabilizing selection. Differences among subpopulations might instead reflect local adaptations driven by divergent selection. These findings signal the need for conservationists to view these subpopulations as unique units of management.

Place, publisher, year, edition, pages
2016. , p. 9
Keywords [en]
Ecology, Esox lucius, evolution, meristic characters, pleomerism, selection
National Category
Ecology Evolutionary Biology
Identifiers
URN: urn:nbn:se:lnu:diva-58621OAI: oai:DiVA.org:lnu-58621DiVA, id: diva2:1051436
Subject / course
Biology
Educational program
Biology Programme, 180 credits
Supervisors
Examiners
Available from: 2016-12-05 Created: 2016-12-01 Last updated: 2016-12-05Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
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