Canal-U

[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 and intra-population genetic variation in early fitness traits in Betula pendula along a latitudinal gradient including marginal southern populations.

In the face of the ongoing climatic crisis, phenotypic plasticity is expected to be crucial to respond to a new environment by increasing the 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 phenotypic plasticity and among-population genetic variation in Betula pendula in early-life traits, (2) to explore potential geographic and environmental factors associated with the observed population genetic divergence at early-life traits, and (3) to estimate levels of within-population genetic variation at those traits.

Betula pendula is a forest tree species with a wide and continuous distribution in central and northern Europe, being restricted to disjunct mountain areas in the Mediterranean Basin.

Different selective pressures across the species range may have resulted in adaptive genetic divergence among populations, including variation at early fitness traits that are critical for recruitment and population persistence under future climatic conditions.

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

We conducted a chamber experiment to evaluate germination rates under controlled conditions.

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

Results: We found that germination rates in the chamber were correlated with those in the common gardens. However, a strong reduction in germination rates was observed under field conditions, 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 as well as population-by-site interactions. Three populations from the centre of the species distribution germinated substantially more than the others. Southern populations had particularly low germination. In fact, germination rate showed a positive association with latitude.

The German site was the only one where a proportion of seedlings survived at the end of the experiment but populations did not differ in final survival rates.

Growth and phenology traits showed significant differences among populations, but the differences did not show a clear association with climate and geography.

At intra-population level, all studied traits showed significant differences among families.

Discussion: Our results highlight the importance of field experiments to obtain realistic information on genetic variation of tree populations and divergence at early life stages.

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

High genetic differentiation among populations in growth and phenology traits, as well as the presence of genetic variation at intrapopulation level in all studied traits, provided evidence for adaptive divergence at the early-life stages in this species and suggest that such traits have evolutionary potential in response to natural selection.

Further research, including replications over seed-crops and environmental conditions, will be necessary to fully understand the regeneration capacity of the species under climate change.