Lower spatial turnover of rare fungal taxa dominantly shaped by
stochastic processes in grassland soils
Abstract
The spatial pattern and community assembly of soil microbial taxa have
notable meanings for biodiversity shaping and maintaining mechanisms.
Rare fungal taxa may exhibit distinct patterns and assembly mechanisms
compared to abundant taxa, but such information is limited, especially
at large scales. Here, we investigated distance-decay patterns and
underlying assembly mechanisms for abundant and rare fungal taxa in 129
soil samples collected across 4,000 km in Chinese Northern grasslands,
based on high-throughput sequencing data. A total of 208 abundant OTUs
(relative abundance > 0.1%, 2.73% of entire OTUs) and
5,779 rare OTUs (relative abundance < 0.01%, 75.85% of
entire OTUs) were identified. Both abundant and rare fungal taxa showed
significant distance-decay relationships (P < 0.001), but the
turnover rate for rare taxa (0.0024 per 100 km) was nearly half that of
abundant taxa (0.0054 per 100 km) based on the binary Bray-Curtis
distance. The lower turnover of rare fungal taxa was likely due to their
community assembly mechanism dominated by stochastic processes, which
were less influenced by environmental gradients. In contrast, abundant
taxa assembly was dominated by deterministic factors like soil variables
and plant traits, which varied significantly along the geographic
distance. Consistently, rare fungal taxa were also less sensitive to
environmental changes, with a lower turnover rate by environmental
distance (0.0027 vs. 0.0099) than abundant taxa. In summary, our
findings revealed that rare fungal taxa, shaped mainly by stochastic
processes, had lower spatial turnover compared to abundant taxa,
dominated by deterministic processes, enhancing our understanding of
rare microbial biogeography.