ORAL PRESENTATION: Adaptive rangewide latitudinal divergence but no evidence of finer-scale local adaptation in early-life traits in Pinus sylvestris

Submitted by : Fady Bruno
Abstract type : Oral presentation
Session type : Conference session 2: LOCAL ADAPTATION of CLIMATE CHANGE-RELATED TRAITS
Author Speaker : José Alberto Ramírez-Valiente

Information about other authors :

Solé A, Cervantes-Arango S, Danusevicius D, Heer K, Notivol E, Opgenoorth L, Pyhäjärvi T, Savolaninen O, Robledo-Arnuncio JJ

Abstract :

The ability of forest tree populations to respond to climate change is yet uncertain. Early-life stages are particularly vulnerable to environmental changes. Common gardens, reciprocal transplants, and provenance trials have been widely used to explore how forest tree species respond to climate. However, such studies usually focus on juvenile or adult responses, overlooking early stages of development, which are critical determinants of the regeneration niche. In this study, we test the extent to which populations of Pinus sylvestris genetically differ in early phenotypic traits and early fitness components across its distribution range, and evaluate the potential role of climate in driving adaptive divergence. We conducted a multi-site common garden experiment,  sowing a total of 24,000 seeds from eighteen populations at four contrasting field sites spanning the latitudinal and climatic range of the species in Europe. Seedling emergence, survival, growth, and phenology were monitored over two years. Results revealed population-by-site interaction for all studied traits and fitness components. We found clinal variation in drought resistance across the species range associated with the temperature of origin of the populations. Populations originating from warmer sites had the highest probability of survival and overall fitness in the southern sites, whereas populations originating from colder areas had the highest overall fitness in the northernmost site. These results suggest that environmental conditions have exerted strong selective pressures on early-life stages in Pinus sylvestris, and that population differences in fitness are probably the result of the evolution under contrasting climates. However, we did not find support for local adaptation over smaller scales. Local populations did not exhibit the highest fitness in their home environments. In the Lithuanian site, for instance, the local population (together with a Norwegian population) had the lowest emergence and survival rates in 2017, as well as the lowest overall performance (together with a French population) over the two years of the experiment. In summary, our study suggests that regional climate has exerted strong selective pressures on Pinus sylvestris over a broad latitudinal gradient, driving the genetic differentiation of populations in traits important for fitness during the first stages of seedling development. Biotic and abiotic factors other than the ones acting at our study sites during the study period have probably driven patterns of local adaptation at smaller scales. In addition, other evolutionary forces such as gene flow and genetic drift might have hampered local adaptation at such finer scales.

Bibliografic references :

Keywords : local adaptation, adaptive divergence, natural selection, evolution, clinal variation, population differentiation
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