Soil pH drives the phylogenetic clustering of the arbuscular mycorrhizal fungal community across subtropical and tropical pepper fields of China

Little is known about the distribution of the arbuscular mycorrhizal fungal (AMF) community along the precipitation gradient in tropical zones, especially croplands. We analysed the AMF community in root and rhizosphere soil samples of pepper (Capsicum annuum L.) from rotation and continuous cropping systems along an annual precipitation gradient of 950-1828 mm from subtropical to tropical zone of China and explored its relationships with environmental variables. Precipitation and soil pH were found to be the main factors that drive the AMF community structuring. Acaulosporaceae was found to be the most abundant family, with its lowest relative abundance (RA) at the lowest precipitation (950 mm). The RA of Glomeraceae in roots was found to be the highest under a precipitation level of 1611 mm. Typically, AMF communities were phylogenetically clustered, and the phylogenetic relatedness was mainly driven by precipitation and soil pH. Moreover, precipitation was found to be positively correlated with phylogenetic relatedness. The operational taxonomic unit richness was lower in the rotation than in the continuous cropping system with lower soil-available phosphorus, whereas cropping systems mainly influenced the RA of AMF families in pepper roots. Our findings suggest the importance of habitat filtering in AMF community structuring along the precipitation gradient. Rice cultivation in the rotation system and with high soil-available phosphorus content may limit the sustenance of AMF diversity in subtropical and tropical croplands.