Within-population genotype – Soil interactions drive phenotypic variation in a recovering fir forest from central Mexico

Abstract

Within-population phenotypic variation can be used as a proxy for adaptive potential and individual performance in forest plantations and natural populations. Such variation can be viewed as the sum of genetic factors and their interaction with environmental variation (e.g., soil characteristics), which lead identical genotypes to produce contrasting phenotypes in different environments, and introduced individuals to perform differently from local trees in plantations and test trials. Predicting this variation is of great interest to foresters working with commercially important species. Such is the case of sacred fir (Abies religiosa), a species that is an important source of wood and resin for communities living above 2500 m asl in central Mexico. We determined the contribution of both genetic and soil factors for predicting phenotypic performance of local naturally regenerated (NR) and introduced by reforestation (RF) seedlings in a sacred fir trial test performed by local communities in the Nevado de Toluca National Park. In spite of a low genetic differentiation between plant sources, NR seedlings outperformed RF plants in terms of height, diameter and water use. According to our models, a large part of these differences could be explained by the interaction of genetic, management and edaphic factors within the trial site, with local genotypes using more efficiently the available soil nitrogen than the introduced ones; thus indicating that planting could be changing plant microenvironment and have a measurable phenotypic effect. Association studies between genetic and edaphic variation further suggested that local adaptation might also be occurring at small within-population scales. All such traits, when correctly integrated, may result in fair genome-based phenotypic predictions for small secluded natural populations, which could be at the base of better reforestation practices, and conservation and assisted migration programs.