Response differences of arbuscular mycorrhizal fungi communities in the roots of an aquatic and a semiaquatic species to various flooding regimes

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in wetland habitats, but their diversity and distribution pattern in these habitats is poorly understood. Under varying hydrological conditions, AMF communities in roots of different wetland species may respond differently due to hydrological and to physiological differences among plants. Here we test this hypothesis. AMF colonization intensity and community structure in the roots of two wetland plants with different flood tolerance (one aquatic and one semiaquatic) were characterized along a hydrologic gradient. A fragment covering partial SSU, the whole ITS and partial LSU rDNA region of AMF was amplified, cloned and sequenced from the roots of each host species. A total of 528 AMF sequences were obtained and sorted into 15 taxa based on phylogenetic analyses. A total of nine and 13 taxa, respectively, were found from the aquatic and semiaquatic host species; the AMF compositions of both sets of taxa were very similar. Intensive flooding inhibited the AMF colonization and diversity level in both cases, while moderate flooding caused distinctly different effects between the two wetland species. AMF diversity level in wetland habitat is not necessarily low, even if few morphological structures of AMF are detected in the roots. The effects of hydrologic conditions on AMF communities in wetlands depend on both the flooding intensity and the adaptations of the wetland hosts.