Morpho‑anatomical trait variability of the Norway spruce (Picea abies (L.) Karst.) needles in natural populations along elevational diversity gradient

Abstract

Geographical and climatic characteristics (elevation, mean annual temperature, summer heat: moisture index, evaporation, climatic moisture deficit, growing degree-days, heating degree-days, de Martonne’s aridity index) drive variations in the morphological and anatomical traits of the Norway spruce (Picea abies L. Karst) needle (needle length, needle thickness, needle width, epidermis thickness with cuticle, hypodermis height, central bundle diameter, resin duct diameter, and the number of resin ducts). We studied the pattern of variation in these needle characteristics in 15 Balkan Mountains (BM) and Dinaric Alps (DA) natural populations (altitudes ranging from 1100 to 1860 and from 980 to 1530 m a.s.l., respectively). The needle traits showed significant differentiation between mountain regions, between populations and within populations. The largest contribution of genetic component in phenotypic variation had the needle length, both components had the same share in the needle width, whereas the environmental component of variability had the largest share in the other needle traits. The principal component analysis revealed that anatomical needle traits and the climatic conditions contributed to differences between populations from different mountain regions. An agglomerative hierarchical clustering analysis revealed three dendogram clusters: three BM populations made one cluster, DA populations made the second, whereas seven populations close to the BM populations and five close to the DA populations made the third cluster. Patterns of morpho-anatomical phenotypic variability point to selective mechanisms and adjustments, enable to define the boundaries of climate niches, and may provide a starting point for conservation program according to climate change projections in the Balkan region.