Biogeographic distribution and divergent assembly process of cyanobacterial morphotypes in biocrusts across northwestern China

The patterns of biogeographical distribution and assembly processes of
microbiota are of vital importance for understanding ecological adaptation
and functioning maintenance. However, the role of their morphological
characteristics in microbial assembly is still poorly ascertained. Here,
by integrating high-throughput sequencing and robust extrapolation of
traits, we investigated taxonomic and phylogenetic turnovers of various
cyanobacterial morphotypes in biocrusts to evaluate the contributions of
deterministic and stochastic processes across a large scale of drylands.
The results showed that the non-heterocyst filamentous category dominated
biocrusts in the arid ecosystem and exhibited strong tolerance against
environmental fluctuations. Despite thesignificant distance-decay
relationship of β-diversity detected in all categories, both species
composition and phylogenetic turnover rates of coccoid cyanobacteria were
higher than non-heterocyst filamentous and heterocystous morphotypes.
Moreover, the assembly of cyanobacteria was driven by different ecological
processes that the entire community and non-heterocyst filamentous
morphotype were governed by deterministic processes, while stochasticity
prevailed in heterocystous and coccoid cyanobacteria. However, aridity can
modulate the balance between determinism and stochasticity and prompt a
shifting threshold among morphotypes, generating an alteration in
community composition. Our findings provide a unique perspective to
understanding the role of microbial morphology in community assembly,
highlighting the differentiation of biogeographic distribution,
environmental response, and species preference between cyanobacterial
morphotypes with consideration of potential functional consequences.