Biogeographical constraints in Glomeromycotinan distribution across forest habitats in China

Glomeromycotinan fungi associate with plant roots in a ubiquitous mutualism, the arbuscular mycorrhiza. Vegetation type, spatial distance, and environmental variability represent the three main factors shaping the structure of Glomeromycotinan communities. We present here one of the most comprehensive reports on Glomeromycotinan community structure in forest ecosystems, covering five ecosystem types. We explored the extent to which the latitudinal gradient in Glomeromycotinan diversity is confounded by the respective latitudinal gradient of host plants and how Glomeromycotinan communities diverge with spatial distance and environmental variability. We show that latitudinal differences in Glomeromycotinan alpha- and beta-diversity are largely shaped by the zonation patterns of ecosystem types and that differences among Glomeromycotinan communities occurring in different ecosystems are considerably larger than those occurring within the same ecosystem type. In contrast, we could observe little to no differences in phylogenetic community structure across samples, irrespective of their origin. In conclusion, several community assembly rules for Glomeromycotina in the woody systems, such as phylogenetic relationships, differed from those in grassland systems. Synthesis. We provide strong evidence that the latitudinal gradient in Glomeromycotinan diversity in woody systems is mainly driven by latitudinal differences in forest habitat types. Further exploring the causes of these differences across habitat types would probably reveal underexplored facets of the ecology of arbuscular mycorrhizal fungi.