[COLLOQUE] GENTREE Final Conference 27-31 January 2020 séance 14

GENTREE Final Conference :

Aida SOLÉ MEDINA - CIFOR-INIA Madrid · Spain

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/

Aida SOLÉ MEDINA - CIFOR-INIA Madrid · Spain : Inter andintra-population genetic variation in early fitness traits in Betulapendula along a latitudinal gradient including marginal southernpopulations.

In the face of the ongoing climatic crisis, phenotypic plasticity isexpected to be crucial to respond to a new environment by increasingthe climatic tolerance of genotypes.

Nevertheless, in the long term,the response to climate change might rely more on adaptive evolution,for which inter-and intrapopulation genetic variation are essential.

The aims of this study were (1) to assess levels of phenotypicplasticity and among-population genetic variation in Betula pendulain early-life traits, (2) to explore potential geographic andenvironmental factors associated with the observed population geneticdivergence at early-life traits, and (3) to estimate levels ofwithin-population genetic variation at those traits.

Betula pendulais a forest tree species with a wide and continuous distribution incentral and northern Europe, being restricted to disjunct mountainareas in the Mediterranean Basin.

Different selective pressuresacross the species range may have resulted in adaptive geneticdivergence among populations, including variation at early fitnesstraits that are critical for recruitment and population persistenceunder future climatic conditions.

Material & Methods: Wecollected seeds from 15 Betula pendula populations across thelatitudinal range of the species (41-55ºN).

We conducted a chamberexperiment to evaluate germination rates under controlled conditions.

Then, we established common garden experiments at three contrastingsites in Lithuania, Germany and Spain where we monitored germination,survival, growth and phenological traits under seminatural conditionsover one year.

Results: We found that germination rates in thechamber were correlated with those in the common gardens. However, astrong reduction in germination rates was observed under fieldconditions, with an approximately ten-fold reduction in Germany,100-fold reduction in Spain, and null germination in Lithuania.

Germination rates exhibited genetic differences among populations aswell as population-by-site interactions. Three populations from thecentre of the species distribution germinated substantially more thanthe others. Southern populations had particularly low germination. Infact, germination rate showed a positive association with latitude.

The German site was the only one where a proportion of seedlingssurvived at the end of the experiment but populations did not differin final survival rates.

Growth and phenology traits showedsignificant differences among populations, but the differences didnot show a clear association with climate and geography.

Atintra-population level, all studied traits showed significantdifferences among families.

Discussion: Our results highlight theimportance of field experiments to obtain realistic information ongenetic variation of tree populations and divergence at early lifestages.

Populations exhibited strikingly low germination and survivalrates in sites experiencing seasonal drought, in particular,southernmost populations, suggesting a limited regeneration capacityfor these populations under dry conditions.

High geneticdifferentiation among populations in growth and phenology traits, aswell as the presence of genetic variation at intrapopulation level inall studied traits, provided evidence for adaptive divergence at theearly-life stages in this species and suggest that such traits haveevolutionary potential in response to natural selection.

Furtherresearch, including replications over seed-crops and environmentalconditions, will be necessary to fully understand the regenerationcapacity of the species under climate change.