Species level patterns in13C and15N abundance of ectomycorrhizal and saprotrophic fungal sporocarps

The natural abundance of 13 C ( δ 13 C) and 15 N ( δ 15 N) of saprotrophic and ectomycorrhizal (ECM) fungi has been investigated on a number of occasions, but the significance of observed differences within and between the two trophic groups remains unclear.• Here, we examine the influence of taxonomy, site, host and time upon isotopic data from 135 fungal species collected at two forest sites in Sweden.• Mean δ 13 C and δ 15 N values differed significantly between ECM and saprotrophic fungi, with only a small degree of overlap even at the species level.Among ECM fungi, intraspecific variation in δ 15 N was low compared with interspecific and intergeneric variation.Significant variation due to site, year and host association was found.• At broad scales a number of factors clearly influence δ 13 C and δ 15 N values making interpretation problematic.We suggest that values are essentially site-specific within the two trophic groups, but that species-level patterns exist potentially reflecting ecophysiological attributes of species.The species is therefore highlighted as the taxonomic level at which most information may be obtained from fungal δ 13 C and δ 15 N data.