Molecular analysis of AMF diversity in aquatic macrophytes: A comparison of oligotrophic and utra-oligotrophic lakes
Résumé
This study aimed to assess AMF diversity in various plant species in lakes with low and relatively high P concentrations to elucidate possible correlations with environmental factors in order for better understanding the functioning of mycorrhizal fungi in submerged plants. A considerable diversity of AMF communities was observed in the lakes with low dissolved P concentrations, especially in the roots of Littorella uniflora. Glomus group A, Archaeospora and Acaulospora were the most frequent and diverse AMF lineages with eight, seven and four phylotypes at Littorella uniflora in at least six lakes with low dissolved P concentrations. In theses lakes, AMF were for the first time observed in the roots of J. bulbosus, a member of a family previously thought to be non-mycorrhizal. In the lakes with relatively high dissolved P concentrations, the frequency decreased from Acaulospora, found at three locations, to Archaeospora at two locations and Glomus group A and Paraglomus at one location.All chemical parameters of the surface water layer, except pH, revealed significant (p <= 0.01) differences between the lakes with low and relatively high dissolved P concentrations. Mean Mg(2+), Ca(2+), K(+), NH(4)(+), CO(2). o-PO(4)(3-) and HCO(3)(-) were 3, 13.5, 15.7, 19.5, 31 and 42.6 times higher, respectively, in the lakes with relatively high dissolved P concentrations compared to the lakes with low dissolved P concentrations. AMF occurred more abundantly with low phosphate and high redox values in the lakes than with high phosphate and low redox values. The pH-value, the total-calcium and total-phosphorus concentrations were strongly correlated with the occurrence of Glomus phylotypes 4 and Archaeospora phylotypes 5 and 8, and a bit less with Acaulospora phylotype 4 and Archaeospora phylotype 3. In such lakes the presence of a diverse AMF community still enables the uptake of sufficient P for isoetid plant species despite the prevailing 'ultra-oligotrophic' conditions. As a consequence, macrophyte plant communities in lakes with relatively high dissolved P concentrations are less dependent on AMF colonization for their development