Heritable variation in the survival of seedlings from Patagonian cypress marginal xeric populations coping with drought and extreme cold

The rear edges of tree species have begun to be perceived as highly valuable for genetic resources conservation and management. In view of expected climatic changes, the responses of trees at their xeric limits may largely be determined by their capacity to cope with augmented environmental variance.We assess the heritability of early survival of Patagonian cypress in two common-garden field tests with contrasting summer water deficits, comprising 140 and 163 open-pollinated families from 10 marginal xeric populations. The first experiment underwent less rigorous conditions than the average mesic, Mediterranean climatic conditions, which were sufficient to reveal additive genetic effects of summer drought on seedling survival. The second trial suffered strong summer water-deficit stress and a winter extreme cold event. In this harsher environment, the heritabilities of survival under summer water-deficit stress were high in all the populations (h200.84 on average), while the heritabilities of seasonal, extreme cold survival were moderate or even nil (h200.28 on average). We did not find evidence of genetic differentiation among populations in their capabilities to survive droughts and cold extremes. Our results indicate that even when climatic changes were strong enough to cause the extinction of the most threatened populations, heritable variation for traits underlying drought and cold tolerances may allow the marginal xeric edge of cypress to persist under augmented environmental variance, without losing overall genetic diversity.Estación Experimental Agropecuaria BarilocheFil: Aparicio, Alejandro Gabriel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Genética Ecológica y Mejoramiento Forestal; ArgentinaFil: Zuki, Sebastián Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pastorino, Mario Juan. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Martinez Meier, Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Ecología Forestal; ArgentinaFil: Gallo, Leonardo Ariel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche. Área de Recursos Forestales. Grupo de Genética Ecológica y Mejoramiento Forestal; Argentin

Genetic versus environmental contributions to variation in seedling resprouting in Nothofagus obliqua

Resprouting is an almost universal functional trait in temperate angiosperms and confers persistence at an individual level after the loss of above-ground biomass. The importance of genetic versus environmental sources of intraspecific variation in resprouting traits is largely unknown. We conducted two genetic field trials, 400 m apart in altitude, in order to sequentially assess seedling resprouting in four environmentally contrasting Argentinean populations of Nothofagus obliqua Mirb. (Oerst). We also performed one nursery test to determine whether populations differed in early root/shoot biomass partition, a key trade-off affecting resprouting. Initial resprouting vigour and final survival were higher in our warmer test site, located 300 m below the core range of the species. The main contrasts between populations were found for pre-clipping seedling size and resprouting profusion, the latter trait showing a clear trade-off with resprouting vigour. Site × population interactions were due mainly to the behaviour of the highest altitude population, suggesting its divergent adaptive trajectory and higher plasticity for resprouting traits. Within populations, trait heritability was low, in general. Episodic frost, which may limit resprouting vigour and final success, had a lower incidence in the altitudinal and xeric limit populations. Overall, our work revealed genetic variation between populations of N. obliqua in traits that determine the success of seedling resprouting, probably associated with divergent selection. Low trait heritability suggests limited in situ micro-evolutionary capacities for resprouting traits under ongoing climate warming; phenotypic plasticity may play an important role in population persistence at the low positions of the elevation gradients N. obliqua currently inhabits.EEA BarilocheFil: Aparicio, Alejandro Gabriel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estacion Experimental Agropecuaria Bariloche; ArgentinaFil: Zuki, Sebastián Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Azpilicueta, Maria Marta. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Barbero, Fernando Alvaro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Pastorino, Mario Juan. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentin