Intraspecific variation in ¹³⁷Cs activity concentration in sporocarps of Suillus variegatus in seven Swedish populations

Abstract

Following the Chernobyl accident in 1986, sporocarps of Suillus variegatus in Sweden showed a large amount of individual variation in concentration of ¹³⁷Cs activity. Our aim was to determine the degrees to which this variability in sporocarp ¹³⁷Cs levels could be explained by differences between (i) local populations, (ii) fungal genets and (iii) locations within genets. Five populations in a 100-yr-old Scots pine forest, located within a 1 km² area, and two populations in Scots pine/Norway spruce forest, located 40 km north-west of Uppsala, were investigated. In total, 154 sporocarps were analysed to determine their ¹³⁷Cs content. Of these, the genetic affiliations of 86 were successfully characterized using somatic incompatibility reactions. Twenty-six genets were found which, on average, consisted of 6·5 sporocarps. The genets averaged 7·5 m in size, measured as the length between the most distant sporocarps. The mean sporocarp ¹³⁷Cs level was 67·1±2·8 kBq kg⁻¹ D.W. (range between 13·6 and 182). According to analyses of variance, within-population variation accounted for 60% of the total variation in ¹³⁷Cs levels, while 40% was ascribed to variation among populations. Within a population, ¹³⁷Cs levels did not generally differ significantly between genets. Plausible reasons for intraspecific variation in radiocaesium content in sporocarps are discussed.