Evolutionary Potential To Face Future Climatic Change Of Two Ecologically Contrasting Southern Beeches.

MARCHELLI P, AZPILICUETA MM, VAN ZONNEVELD M, GALLO, LA

Congreso; Evoltree Conference “Forest Ecosystem Genomics and Adaptation”; 2010

The ability of populations to adapt to climate change depends on their genetic diversity as well as their plasticity. In northern Patagonia, aridity is predicted to increase due to a combination of an increase in mean temperatures and a decrease in precipitation. Rauli beech (Nothofagus nervosa) and Roble beech (Nothofagus obliqua) both occur in this area but occupy different ecological niches: the former is more tolerant of cold and shade while the latter is more resistant to drought and high temperatures. Adaptation to the new environmental conditions will only be possible if sufficient and appropriately distributed genetic diversity is available for an evolutionary response. We aimed to identify the vulnerability of the different populations in order to provide guidelines for conservation and domestication programmes. We collected 452 individuals from 13 populations along a moisture gradient (1200–3000 mm/year) and genotyped them using seven nuclear microsatellites on an ABIPRISM 3700 capillary sequencer. This showed the species to be highly differentiated (AMOVA: 0.346, P = 0.001), with N. nervosa being more diverse than N. obliqua (14 vs 7 private alleles, allelic richness 43.4 vs 39.8, H = 0.396 vs 0.260). Bayesian clustering detected a maximum likelihood of four groups, with almost all (95.2 %) individuals of N. obliqua within a single cluster. We estimated the allelic richness for each population and mapped the potential shift in their distribution with DIVA GIS under the predicted climatic conditions for 2050 under emission scenario A2 according to the average projection of three general circulation models (HadCM3, CCCma and CSIRO). Nothofagus obliqua showed greatest genetic diversity in eastern populations under more xeric conditions, while N. nervosa was more variable in western, humid locations. This confirms previous findings using chloroplast and isozyme gene markers. The results also agree with the ecological requirements of both species and suggest that conserving the current hotspots of diversity will sustain the evolutionary potential of both species, since altitudinal migration should be possible in N. nervosa and longitudinal migration in N. obliqua.