Text by Leila Pazouki and Ülo Niinemets
A manuscript by Leila Pazouki, Parvin Salehi Shanjani, Peter D. Fields, Karina Martins, Marina Suhhorutšenko, Haldja Viinalass and Ülo Niinemets characterizing the genetic diversity of key Estonian forest species Pinus sylvestris at its soil fertility limit using nuclear and chloroplast microsatellite markers, has been published in European Journal of Forest Research.
Full citation: Leila Pazouki, Parvin Salehi Shanjani, Peter D. Fields, Karina Martins, Marina Suhhorutšenko, Haldja Viinalass & Ülo Niinemets (2015) Large within-population genetic diversity of the widespread conifer Pinus sylvestris at its soil fertility limit characterized by nuclear and chloroplast microsatellite markers. European Journal of Forest Research, 10.1007/s10342-015-0928-5 (link to full text)
Fig 1. Location of sampling sites for three natural bog populations of Pinus sylvestris in Estonia and demonstration of tree sampling along the trails from drier (1) to wetter (60) habitats. Pie graphs refer to cpDNA haplotypes frequencies. (graph from the paper)
Scots pine (Pinus sylvestris) is the only pine species native to northern Europe, and it is the most common tree species in the Baltic states. In Estonia, P. sylvestris covers almost 38% of Estonian forests and is the key dominant species in extremely infertile raised bogs. In this study, genetic variability and population structure of P. sylvestris were analyzed in three distant naturally-seeded bog populations that can be considered as the fertility limit of this species. In each site, the samples were collected along a soil fertility gradient from drier bog margins towards wetter bog interiors to characterize the small-scale variability in sub-population genetic structure. We hypothesized that there is high level of outbreeding and consequently high genetic variability at the nutrient limit of the species, and further that there is a spatial gradient in genetic relatedness indicative of the genetic component of phenotypic plasticity in the organic-mineral soil continuum. These hypotheses were partly supported by data that indicated greater within- than among-population variability and a certain spatial population structuring. This study provides important insight into the overall genetic variability and sub-population differentiation in nutrient-limited sites. This information is of crucial value in understanding species adaptability to environmental heterogeneity and has important practical applications in selecting plant sources suitable for reforestation. Especially for reforestation of nutrient-limited habitats, e.g., degraded habitats where tree growth is particularly strongly curbed by limited soil fertility.
This is the first genetics paper from the plant physiology work group in EMÜ!
Genetic variation is an important attribute of forest tree populations enabling them to adapt to spatial and temporal variations in environmental conditions. In particular, Scots pine (Pinus sylvestris L.) has an exceptionally broad area of dispersal covering different climates and soil conditions, but the genetic variability in extreme conditions has not been studied. We hypothesized that the genetic variability of P. sylvestris is enhanced at its soil fertility limit in bogs where stunted trees form a sparse canopy with reduced light competition, but in highly turbulent conditions generating ideal conditions for distant pollen dispersal. A total of 180 individuals were studied from three bog populations using five nuclear (nSSR) and five chloroplastic (cpSSR) polymorphic microsatellite loci (simple sequence repeats, SSR). According to both marker systems, high and similar level of genetic diversity (ca. 99 % within the populations and 1 % among the populations) was observed for nuclear (F ST = 0.007 and R ST = 0.022) and chloroplast (F ST = 0.015 and R ST = 0.023) genomes. Despite the low genetic differentiation among the populations, there was evidence of geographic genetic differentiation in the chloroplast genomes, suggesting that isolation by distance might be a possible mechanism shaping the present distribution of genetic variability. In addition, significant but low spatial genetic structure along habitat wetness gradient was found in nuclear genomes in one site. Significant cyto-nuclear linkage disequilibrium was shown between one of the cpSSR loci to all nSSR loci. The results demonstrate a huge within-population genetic variability in these sites and underscore the importance of pollen gene flow in homogenizing populations on these geographic scales.