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Adaptive mechanisms of ecological divergence in sibling allopolyploid lineages

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DNA doubling = adaptive success

The spotted orchid or Dactylorhiza species is not only beautiful, it can live in a range of habitats, from the Alps to fresh industrial waste. Prone to hybridisation and chromosome doubling, its constantly changing genetics are the key to this orchid's colonisation prowess.

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Hybridisation followed by whole genome doubling (WGD) is thought to be responsible for kick-starting evolution in flowering plants. Multiplying the chromosome number in a newly formed hybrid species gives rise to so-called allopolyploidy. This is usually followed by genome and epigenome changes for better adaptive success. The POLYADAPTATION (Adaptive mechanisms of ecological divergence in sibling allopolyploid lineages) project has investigated the genetics of sibling Dactylorhiza allopolyploids. The goal was to identify how these iterative merger events have enabled adaptation to different ecological niches. Analysing around one million nucleotide bases, the researchers found a genome-wide absence of genetic differentiation despite visibly obvious phenotype differences. However, looking at four different species, there was a very weak geographic signal whereby British and Scandinavian lines could be distinguished. This suggests that when geographic barriers are weak, there is asymmetric gene flow between the polyploids which works against genetic differentiation. For more details, see Allopolyploid evolution in Dactylorhiza. The researchers have also investigated how recurring WGD may trigger altered gene expression and alter ecological properties. Increased overexpression of genes was evident in a more recently evolved species than in a species that more closely resembled the diploid parents. Also relevant is an initiative outside the funding of the POLYADAPTATION project, but at the same time has given rise to the group Plant Ecological Genomics at the University of Vienna. Using a START award, two prestigious symposia were also organised by POLYADAPTATION researchers. These are the Evolutionary Epigenetics at the XVIII International Botanical Congress, Melbourne, Australia in 2011 and at the BioSystEU2013, Vienna, Austria in 2013. POLYADAPTATION research results have provided insight on the role of polyploidy in evolution that are highly relevant to adaptation and speciation. The links between polyploidy and functional diversity promise to shed light on genetic and epigenetic mechanisms within a plant population.


Dactylorhiza, hybridisation, whole genome doubling, allopolyploidy, epigenome

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