Ecological and evolutionary role of a persistent soil seed bank in perennial herbaceous plant species
Final Report Abstract
Using amplified fragment length polymorphisms (AFLP) and methylation sensitive fragment length polymorphism (MSAP), we studied two different but potentially complemental plant strategies to cope with the spatial and temporal dynamics of their environment and hence, to ultimately ensure their long term persistence under fluctuating conditions. Surveying populations of the cleistogamous V. elatior at the two endpoints of a successional gradient, we specifically investigated (i) the impact of persistent seedbanks on population genetic stability, and (ii) the importance of epigenetic variation for environmental adjustment and/or adaptation. Regarding the impact of persistent seedbanks (SB) our results indicate that in V. elatior relative SB genetic diversity (i.e. compared to standing plant diversity) increases with ongoing succession and despite decreasing population size. Thus, strikingly the SB genetic capacity to counteract the detrimental effects of drift and selection seems to rise with decreasing habitat suitability. In late successional habitats with a high risk of extinction, this increased relative SB genetic diversity furthermore assures a higher chance for population recovery after potential disturbance events. Corroborated by much lower small-scale genetic structure in late than in early successional habitats, we suggest that the observed change in relative SB diversity is initially driven by a change in outcrossing rates along the gradient. Comparing genetic and epigenetic variation, revealed slightly lower genetic (H’gen = 0.19) than epigenetic (H’gen = 0.23) diversity, and higher genetic (ϕST = 0.72) than epigenetic (ϕST = 0.51) population differentiation. However, both, diversity and differentiation were significantly correlated, indicating that epigenetic variation partly depends on the same driving forces as genetic variation. But still, genome scan analysis, principal coordinates analysis and Mantel tests showed that overall epigenetic variation was more closely related to habitat conditions than genetic variation. This suggests that environmentally induced methylation changes may lead to a convergence of populations experiencing similar habitat conditions and thus may play a major role for the transient and/or heritable adjustment to changing environments. Additionally, using a new MSAP-scoring approach, we found that mainly the unmethylated (ϕST = 0.60) and CG-methylated states (ϕST = 0.46) of epiloci contributed to population differentiation and putative habitat-related adaptation, whereas CHG-hemimethylated states (ϕST = 0.21) only played a marginal role.
Publications
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2013. Scoring and analysis of methylation sensitive amplification polymorphisms (MSAP) for epigenetic population studies. - Molecular Ecology Resources 13: 642-653
Schulz, B., Eckstein, R.L., Durka, W.
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2014. Epigenetic variation reflects dynamic habitat conditions in a rare floodplain herb. - Molecular Ecology 23: 3523-3537
Schulz, B., Eckstein, R.L., Durka, W.
