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.
Important for ecosystem functionality and equilibrium, the microbial
rare taxa may have distinct spatial patterns and community assembly
mechanisms from those of abundant taxa. However, such information is
lacking, especially for rare fungal taxa 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%) and 5,779 rare OTUs (relative abundance
< 0.01%) were obtained, accounting for 2.73% and 75.85% of
entire OTUs, respectively. Community similarities of abundant and rare
fungal taxa both declined significantly (P < 0.001) with the
increasing geographic distance, following the distance-decay
relationship. However, the turnover rate for rare fungal taxa (0.0024
per 100 km) was almost half of that for the abundant taxa (0.0054 per
100 km) based on the binary Bray-Curtis distance. Such lower turnover
for rare fungal taxa was likely due to their community assembly
mechanism dominated by stochastic processes, which were less influenced
by environmental variance along the geographic distance. In contrast,
the assembly of abundant fungal taxa was dominated by deterministic
factors including soil variables and plant traits, which changed greatly
along the geographic distance. Consistently, the rare fungal taxa were
less sensitive to environmental changes spatially since their turnover
rate by the environmental distance was much lower than that of abundant
taxa (0.0027 Vs 0.0099). In summary, our findings revealed that rare
fungal taxa shaped mainly by stochastic processes had lower spatial
turnover than abundant fungal taxa shaped by deterministic processes,
which enhanced our understanding of the biogeography for rare microbial
taxa.