Global Biogeography of Prokaryotes in Mangrove Sediments: Spatial Patterns and Ecological Insights from 16S rDNA Metabarcoding

The global asymmetry in the floristic diversity distribution within mangrove ecosystems is well-documented. However, sediment microbial communities, which play crucial ecological roles, are often overlooked in mangrove biogeography studies. This study aimed to investigate the diversity, composition, and distribution of prokaryotic communities across distinct mangrove bioregions (12 countries and territories from the Caribbean bioregion, Southeast America, East Africa, Indo-Malaysia and Australasia). We conducted a meta-analysis by compiling 16S rDNA datasets from 17 previous studies (540 samples) over a six year period (2014-2020) and applied community ecology analyses combined with random forest models. Although no significant correlation was observed between tree richness and microbial diversity, a microbial hotspot was identified in the Indo-West Pacific region. Microbiota associated with different mangroves displayed opposite latitudinal diversity gradients and beta-dispersions. Distance-decay relationships were weak but statistically significant. Random forest models identified key microbial taxa, and the OTUs shared across all bioregions suggested the presence of a potential core mangrove microbiota. Taxonomic and statistical analyses underscored the great heterogeneity of microbiota composition, heavily influenced by the study (e.g., molecular and bioinformatic methodologies). Future research on mangrove microbiome would benefit from standardized sampling and sequencing methods. Despite current limitations, distance-decay relationship confirmed the influence of dispersal barriers for mangrove sediment microbiota. This study also suggests that environmental factors, rather than plant diversity alone, may play a prominent role in shaping the diversity, composition and distribution of prokaryotic communities in mangrove sediments.