[COLLOQUE] GENTREE Final Conference 27-31 January 2020 séance 7

GENTREE Final Conference : Katharina BUDDE - INRAE Bordeaux · France

GENTREE Final Conference 'Genetics to the rescue - managing forests sustainably in a changing environment'

27-31 January 2020, Avignon, France

http://www.gentree-h2020.eu/

Katharina BUDDE - INRAE Bordeaux · France : Range wide geneticvariation and divergence in Pinus pinaster elucidated by gene capturedata

The population genetic structure of tree species has often beenstudied using neutral genetic markers; however, little is known abouthow genetic diversity at potentially adaptive loci is distributed innatural forest tree populations.

Comparing closely related specieswith different life history traits or distantly related species withsimilar life history traits could reveal mechanisms and driversshaping genetic adaptations.

Yeaman et al. (2016) reported convergentevolution at several loci associated with similar climatic clines intwo distantly related conifer species in North America.

In twoclosely related European pine species (Pinus pinaster and P.sylvestris) occupying different ecological niches and with differentevolutionary histories, Grivet et al. (2017) revealed unusually highrates of adaptive evolution and several loci under selection in bothspecies. Here we aim to further elucidate adaptive processes in Pinuspinaster and later on compare our results to other European treespecies.

Material and Methods: In the framework of GENTREE H2020project, samples were collected in range wide populations in a pairedsampling design contrasting local stands growing under markedlydifferent conditions (high altitude vs. low altitude or wet vs. dry).

A total of 599 Pinus pinaster samples from 25 populations areavailable. Gene capture data was generated on over 1,130 homologousgenes common to seven deeply sequenced European forest tree species.

For each species, ca. 1,000 extra genes were added comprisingpreviously known candidate genes, as well as random sequences. SNPcalling was done against a de-novo assembly of reads from selectedPinus pinaster samples. STRUCTURE and other spatial analysis methodswere used to identify gene pools and to evaluate distinctness ofmarginal populations, as well the site frequency spectrum wasassessed to reveal the demographic history of the species.

Preliminary selection analyses were also performed . Results: For P.pinaster, the gene capture experiment yielded over 130 000 highquality SNPs after filtering. We used sequences from the haploidtissue of the megagametophytes to identify loci with paralogs andcompared the results to other approaches commonly used for paralogfiltering e.g. based on heterozygote excess and deviation from allelebalance.

We revealed the population genetic origin of the 25 rangewide populations including populations with great conservationinterest from south-east France, southern Italy, southern Morocco andTunisia which have never been part of phylogeographic studies withnuclear markers before.

Furthermore, we described the demographichistory for multiple and differentiated gene pools in the species, aswell as produced preliminary results on loci associated toenvironmental factors taking advantage of the paired sampling designand the range wide samples.

Conclusions: The high number of genomewide markers allowed us to study the population genetic structure ofP. pinaster in more detail than previous studies, as well as toprovide insight on demographic history of the differentiated genepools in the species.