[COLLOQUE] GENTREE Final Conference 27-31 January 2020 séance 13

GENTREE Final Conference : José Alberto RAMÍREZ-VALIENTE - 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/

José Alberto RAMÍREZ-VALIENTE - CIFOR-INIA Madrid · Spain : Adaptive rangewide latitudinal divergence but no evidence offiner-scale local adaptation in early-life traits in Pinus sylvestris

The ability of forest tree populations to respond to climate changeis yet uncertain.

Early-life stages are particularly vulnerable toenvironmental changes.

Common gardens, reciprocal transplants, andprovenance trials have been widely used to explore how forest treespecies respond to climate.

However, such studies usually focus onjuvenile or adult responses, overlooking early stages of development,which are critical determinants of the regeneration niche. In thisstudy, we test the extent to which populations of Pinus sylvestrisgenetically differ in early phenotypic traits and early fitnesscomponents across its distribution range, and evaluate the potentialrole of climate in driving adaptive divergence.

We conducted amulti-site common garden experiment, sowing a total of 24,000 seedsfrom eighteen populations at four contrasting field sites spanningthe latitudinal and climatic range of the species in Europe. Seedlingemergence, survival, growth, and phenology were monitored over twoyears. Results revealed population-by-site interaction for allstudied traits and fitness components.

We found clinal variation indrought resistance across the species range associated with thetemperature of origin of the populations. Populations originatingfrom warmer sites had the highest probability of survival and overallfitness in the southern sites, whereas populations originating fromcolder areas had the highest overall fitness in the northernmostsite.

These results suggest that environmental conditions haveexerted strong selective pressures on early-life stages in Pinussylvestris, and that population differences in fitness are probablythe result of the evolution under contrasting climates.

However, wedid not find support for local adaptation over smaller scales. Localpopulations did not exhibit the highest fitness in their homeenvironments.

In the Lithuanian site, for instance, the localpopulation (together with a Norwegian population) had the lowestemergence and survival rates in 2017, as well as the lowest overallperformance (together with a French population) over the two years ofthe experiment. In summary, our study suggests that regional climatehas exerted strong selective pressures on Pinus sylvestris over abroad latitudinal gradient, driving the genetic differentiation ofpopulations in traits important for fitness during the first stagesof seedling development.

Biotic and abiotic factors other than theones acting at our study sites during the study period have probablydriven patterns of local adaptation at smaller scales. In addition,other evolutionary forces such as gene flow and genetic drift mighthave hampered local adaptation at such finer scales.