Variability in seedling emergence traits of Patagonian Cypress marginal steppe populations

Abstract

Genetic information on adaptive traits is crucial for prediction of the evolution of natural populations in relation to global climate change. The seedling emergence process together with germination is a key adaptive stage in any seeding species. We aim to analyze variability in seedling emergence traits within and among marginal populations of Patagonian Cypress (Austrocedrus chilensis (D.Don) Pic. Ser. et Bizzarri), which have been suggested to be of conservation relevance. We performed an emergence trial in a greenhouse with seeds collected from 177 open-pollinated trees from 10 populations. A sigmoidal curve was fitted to the cumulative emergence data (in percentage of the sown seeds) for each replicate of each family. Variability was estimated using ANOVA for six variables: emergence capacity (EC), emergence energy (EE), energy period (EP), emergence initiation (t10), emergence cessation (t90) and emergence duration (Dur). The overall trial mean for EC was 76.2 %, while EE was only 27.6 %. Hence, most seedlings emerged after the energy period, which is interpreted as a bet-hedging strategy. Both “population” and “family” factors significantly affected all variables. The proportions of “family” variances were higher than “population” ones for EC, EE, Dur and t90, but the opposite was found for EP and t10, which is evidence of differentiation among populations. Variability among families may be due to both genetic and environmental causes, including maternal effects. However, the relatively high proportion of family variability in EC and EE suggests acceptable levels of additive genetic variance, which would not hinder the potential to evolve in these specific traits. Conversely, the chances to adapt in EP and t10 are lower, and consequently local extinctions driven by global climate change seem possible.