Provenance Trials of the Mexican Spruces in Nursery Conditions: Three Species Endangered by Climatic Variation

In Mexico there are three endemic species of Picea, living in relict populations and they are listed as “Endangered” on the Red List of the IUCN. P. mexicana has only three locations, above of 3,000 m of altitude. P. martinezii has four populations between 1,800 and 2,500 m and P. chihuahuana has been found in 40 locations between 2,311 and 2,730 m; The Mexican spruces distribution is fragmented in isolated populations, which could lead to phenological, morphological and genetic differentiation partially caused by local adaptation to different soil types and climate changes. Therefore, it is important to identify the main factors accounting for such adaptation, which would be helpful in assisted migration programs as an option to ex situ conservation. In that sense, in this study we examined the effect that the edaphology and climatic variables of different populations have on the growth and survival of each Picea species seedlings in equal nursery condition, assuming that such response on growth could be taken as a proxy of the adaptation or the genetic differentiation among populations. Methods. Considering 22 climatic and 27 edaphology variables from each location we established a provenances trial, in a nursery located at El Salto, Durango; Mexico, where we measured the growth in diameter and height of 5,641 seedlings, during 12 months and the survival. Applying a cluster analysis and a Calculate Pairwise Multiple Comparisons of Mean Rank Sums to calculated differences among locations. The individual heritability (h2i) and the means of family (h2f) were also evaluated. We used the Spearman´s correlation test to analyze the relationships between growth traits and the climatic an edaphology variables from each location. Results. The cluster analysis revealed three populations groups. The Calculate Pairwise Multiple Comparisons of Mean Rank Sums showed significant differences in the genetic quantitative traits between locations within each species. The genetic control on the growth traits was high and correlations between genetic quantitative values and climatic factors were detected.