CONTENS - International Organization of Plant Biosystematists

O 31
Evolutionary responses towards adaptation and speciation after
allopolyploidization in Dactylorhiza (Orchidaceae)
Ovidiu Paun, Mark W. Chase, Javier A. Luna, Robyn Cowan & Michael F. Fay
Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond TW9 3DS, U.K.;
o.paun@kew.org, m.chase@kew.org, javoluna@gmail.com, r.cowan@kew.org,
m.fay@kew.org,
Hybridization and polyploidization are widespread in angiosperms and regularly
stimulate plant evolution, promoting genetic diversity, evolutionary innovation,
adaptive radiation and speciation. An important feature of allopolyploidization is its
potential to occur repeatedly between the same parental taxa, leading to arrays of
allopolyploids that subsequently interbreed. In Dactylorhiza, ecologically divergent
allotetraploids D. majalis, D. traunsteineri and D. ebudensis resulted from
hybridization of diploids D. fuchsii and D. incarnata. In this system we are analysing
consequences of polyploidy and hybridization on natural evolution of the genomes
and adaptation to the environment. A genome-wide survey of the transcriptome at
286 loci using cDNA amplified fragment length polymorphism (cDNA-AFLP),
complemented by investigating epigenetic variation with methylation sensitive AFLP
(MSAP), indicates extensive physical (non-epigenetic) differences in gene expression
between parents and descendants, as well as between allotetraploids. Although no
widespread repeatable loss of low copy DNA sequence is apparent in the hybrids,
there is a significant increase of the number of transcripts expressed at a moment in
time in the polyploids potentially resulting in biological complexity increase. Several
novel transcripts in the polyploids are associated with environmental parameters and
might represent parts of the molecular mechanisms that result in adaptation to
different ecological conditions/habitats enforcing reproductive isolation. In addition to
stabilizing allopolyploid genomes such novel expression patterns along with
increased heterozygosity and gene redundancy might confer on hybrids an elevated
evolutionary potential, with effects at scales ranging from the molecular to the
ecological.
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