Intraspecific variability of Pisolithus spp. as a response to changes in soil characteristics in a Moroccan cork oak plantation

Soil characteristics may be an important factor in structuring fungal communities. We relate the above- and below-ground distribution of the ectomycorrhizal fungi (EMF) Pisolithus spp. to changes in soil chemistry in a Quercus suber plantation located in the Maâmora forest (Morocco). Intrageneric variability of 115 fruit bodies was studied, using morphological characterization, restriction fragment length polymorphism (RFLP) analyses and internal transcribed spacer (ITS) sequencing. Two Pisolithus spp. genotypes were identified: 97% of the fruit bodies represent Pisolithus arhizus; the remaining 3% correspond to Pisolithus species 4, as previously described by Martin et al. [New Phytologist 153 (2002) 345-357]. Multivariate analysis (PCA) showed that species structure was strongly correlated with soil characteristics. P. arhizus fruit bodies were frequently found in the Eastern part of the plot at low molasic clay, N and P contents, while Pisolithus species 4 were collected only in the Western part at the high molasic clay, N and P contents. To determine whether this change in fruit body structure was expressed at the belowground level, we used morphological and molecular techniques to characterize the Pisolithus ectomycorrhizas. Only ectomycorrhizas of P. arhizus were identified at the low P?N?molasic clay site and disappeared completely at the high P?N?red clay site, where no Pisolithus species 4 mycorrhizas were found. However, autocorrelation among soil parameters makes it difficult to isolate the effects of individual parameters. These results show the local-scale impact of natural spatial heterogeneity on an ectomycorrhizal fungal genus.