University of Jyväskylä

Dissertation: 19 Jan 2018: The effect of variation in developmental mode on the population dynamics of a spionid polychaete (Pygospio elegans) in a heterogeneous environment

Start date: Jan 19, 2018 12:00 PM

End date: Jan 19, 2018 03:00 PM

Location: Ylistönrinne, YAA303

Anne ThonigM.Sc. Anne Thonig defends her doctoral dissertation in Ecology and Evolutionary Biology "The effect of variation in developmental mode on the population dynamics of a spionid polychaete (Pygospio elegans) in a heterogeneous environment". Opponent Dr. Frédérique Viard (Station Biologique de Roscoff, France) and custos Dr. K. Emily Knott (University of Jyväskylä). The doctoral dissertation is held in English.

There is a great diversity in larvae of marine invertebrates. To understand the causes and consequences of different modes of development on population dynamics, study of poecilogonous species that show a polymorphism in developmental mode might be more useful than are comparisons between species, since no confounding effects due to speciation arise. In this study, I documented the population ecology and genetics of the poecilogonous polychaete P. elegans and investigated the impact of abiotic and biotic variables on population dynamics. Four focal populations from the Isefjord-Roskilde-Fjord estuary complex, Denmark were sampled over one year. I observed highly dynamic population structure in both size cohort data and population genetic data that is possibly explained by the short life span of P. elegans and sweepstakes reproductive success. Additionally, stochastic events, such as rain storms, can lead to abrupt drops in salinity which can be detrimental for P. elegans and hence introduce further changes in population structure. Seasonal dynamics, including sexual reproduction, were correlated with temperature, whereas spatial differences in density, size and reproductive activity of P. elegans as well as species diversity of the benthic invertebrate community, were related to sediment structure. A positive correlation between species and allelic richness of P. elegans might indicate that environmental impacts are of greater importance in shaping population dynamics than are species interactions. Switches in developmental mode could reflect a strategy for coping with life in an unpredictable, heterogeneous habitat. Although switches in developmental mode were correlated with the appearance of genetically differentiated size cohorts, environmental or epigenetic effects cannot be ruled out.

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Anne Thonig
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