Cold adaptation drives variability in needle structure and anatomy in Pinus sylvestris L. along a 1,900 km temperate–boreal transect

Abstract

Occupancy of cold habitats by evergreen species requires structural modification of photosynthetic organs for stress resistance and longevity. Such modifications have been described at interspecific level, while intraspecific variation has been underexplored. To identify structural and anatomical traits that may be adaptive in cold environments, we studied intraspecific variability of needles of Scots pine (Pinus sylvestris L.), a wide‐ranging tree, along a 1,900 km temperate–boreal transect in Europe. Needles from 20 sites representing mean minimum winter temperatures between −4.0 and −19.9°C and mean annual temperatures between 8.3 and −1.7°C were sampled for measurements of leaf mass per area (LMA, g/m2), leaf density (LD, g/cm3) and 30 other morpho‐anatomical traits. Needles from cold sites lived longer, were shorter, showed higher LMA and LD, had narrower and more collapse‐resistant tracheids, thicker epidermal cells with thicker cell walls and wider resin ducts occupying larger fraction of needle volume in comparison to needles from warmer sites. Along the steep climatic gradient, needles presented a coordinated phenotypic spectrum of external and internal traits that are largely interpretable in functional, adaptive terms. This intraspecific pattern of covarying traits provides insight into the adaptive syndrome associated with stress tolerance and extended needle longevity under cold conditions of high latitudes. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12946/suppinfo is available for this article.

Is Resistance to Mountain Pine Beetle Associated with Genetic Resistance to White Pine Blister Rust in Limber Pine?

“…Resin duct number decreased and relative duct area increased in the wood of trees growing at increasing elevation ( Figure 4) consistent with Wimmer and Grabner's [56] report of fewer resin ducts of Norway spruce from cooler habitats (Picea abies L.). Likewise, the increase in relative duct area with increasing elevation (and therefore lower air temperature; [57]), is similar to the linear relationship between relative duct area in needles and minimum air temperature in Scots pine (P. sylvestris L.) [58] yet different from the curvilinear response of needle duct traits to elevation of P. taiwanensis Hayata [59]. Limber pine invests more in resin duct defenses per unit radial wood growth with increasing elevation, however, resin flow is better predicted by resin duct number and area [24] which decreased in our study with increasing elevation.…”

Red Wood Ants prefer mature Pine Forests in Variscan Granite Environments (Formica rufa-group)

“…There could be mechanical and chemical reasons for the preference of pine needles: Pine needles may have a mechanical advantage in size and structure over individual spruce needles, as pine needles are usually found as a bundle of 2-3 extremely narrow needles per sheath covering the base of the needle bundle. In addition, a greater thickness of outer epidermal walls of pine needles can support mechanical strength and protect the pine needles from desiccation, especially in winter (Jankowski et al 2017). This can support the durability of the nest building material.…”

“…This could additionally contribute to longevity of the nest cover. From a chemical point of view, the thick-walled epidermis contributes to the defense against herbivores by forming specialized resin channels (Jankowski et al 2017). Resin is an important component of RWA nests because of its stabilizing and antibacterial effect (Christe et al 2003).…”

The flattened and needlelike leaves of the pine family (Pinaceae) share a conserved genetic network for adaxial-abaxial polarity but have diverged for photosynthetic adaptation

“…Generally, needlelike leaves appear to be more drought-resistant than flattened leaves [ 5 , 6 ]. Previous studies on conifer “needles” have evaluated their morphology and physiology [ 7 – 9 ] but rarely focused on their developmental mechanisms and evolution. Pinaceae (the pine family), comprising 11 genera and approximately 230 species, is the most important component of the coniferous forests in the Northern Hemisphere, with both needlelike and flattened leaves [ 4 , 10 , 11 ].…”