Genetic variation in architectural seedling traits of Patagonian cypress natural populations from the extremes of a precipitation range

Species distributed along wide environmental ranges are expected to be either plastic or adapted to local optima. The elucidation of which of these alternatives prevails, is crucial in planning breeding and conservation strategies for not yet domesticated species. Austrocedrus chilensis (Cupressaceae) is the most commercially important conifer of the temperate forests of Argentina and the target of a domestication program. A steep precipitation gradient characterizes its Argentinean range.Austrocedrus chilensis (Cupressaceae) is the most commercially important conifer of the temperate forests of Argentina and the target of a domestication program. A steep precipitation gradient characterizes its Argentinean range. • Variation within and differentiation among four natural populations of this Patagonian cypress representative of two contrasting precipitation regimes (>1 300 and 330 mm per y) were assessed by analyzing several morpho/architectural traits in one-year-old seedlings grown in a greenhouse.Variation within and differentiation among four natural populations of this Patagonian cypress representative of two contrasting precipitation regimes (>1 300 and 330 mm per y) were assessed by analyzing several morpho/architectural traits in one-year-old seedlings grown in a greenhouse.>1 300 and 330 mm per y) were assessed by analyzing several morpho/architectural traits in one-year-old seedlings grown in a greenhouse./architectural traits in one-year-old seedlings grown in a greenhouse. • Progenies from one of the two xeric populations did not differ from those corresponding to both humid-site populations. The two most variable populations in terms of additive genetic variance belonged to contrasting precipitation regimes. Differentiation among populations was low as measured by each and every variable (average Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning.Progenies from one of the two xeric populations did not differ from those corresponding to both humid-site populations. The two most variable populations in terms of additive genetic variance belonged to contrasting precipitation regimes. Differentiation among populations was low as measured by each and every variable (average Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning.fferentiation among populations was low as measured by each and every variable (average Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning.Qst = 0.088). Morphological traits related to the main axis size would have a dubious adaptive meaning. • The results suggest that the Patagonian cypress would have not evolved genetic pools adapted to local optima, and thus it appears to be a phenotypically plastic species, at least regarding growth at juvenile age.The results suggest that the Patagonian cypress would have not evolved genetic pools adapted to local optima, and thus it appears to be a phenotypically plastic species, at least regarding growth at juvenile age. • Les espèces presentant de vastes aires de répartition avec des fortes variations de l’environnement sont soit plastiques, soit adaptées à des optima locaux. Identifier laquelle de ces deux alternatives est celle qui prévaut est une étape cruciale pour planifier des stratégies d’amélioration génétique ou de conservation d’espèces non encore domestiquées. Austrocedrus chilensis (Cupressaceae) est le conifère le plus important du point de vue commercial dans les forêts tempérées d’Argentine et fait l’object d’un programme de domestication. Un fort gradient de précipitations caractérise son aire de répartition en Argentine. • Les variations intra-population et la différenciation entre quatre populations naturelles représentatives de deux régimes contrastés de précipitations (>1 300 mm et 330 mm par an) ont été évaluées en analysant plusieurs traits d’architecture et de morphologie sur des plants âgés de un an cultivés sous serre. • Les descendants de l’une des deux populations xériques ne différaient pas de ceux des deux populations de sites humides. Les deux populations avec la plus forte variance génétique additive provenaient de régimes contrastés de précipitation. La différenciation entre populations était faible tant pour chaque trait que pour l’ensemble des traits (Qst = 0.088). Les caractéristiques morphologiques liées à la taille de l’axe principal n’auraient donc que peu signification en termes d’adaptation.• Les résultats suggèrent que le cyprès de Patagonie n’aurait pas développé de pools génétiques adaptés aux optima locaux. Il semble être une espèce phénotypiquement plastique, au moins en ce qui concerne la croissance au stade juvénile. Fil: Pastorino, Mario Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina