Diversidade Filogenética da comunidade de microeucariotos planctônicos da planície de inundação do rio Araguaia por DNA metabarcode

Abstract

Integrating phylogenetic and community ecology studies has proven highly effective in unraveling the ecological and evolutionary processes that shape biodiversity. In this context, combining eDNA metabarcoding with community phylogenetic analyses holds promise for describing patterns of community organization and assembly, providing more robust and informative estimates of diversity. This study aimed to investigate the phylogenetic diversity of the eukaryotic community captured by the 18S molecular marker in the Araguaia River floodplain, using the metabarcoding technique. Focusing on groups of photosynthetic planktonic microeukaryotes (PPME), we sought to understand how environmental and spatial factors influence the diversity and phylogenetic structure of these communities. To this end, water samples were collected from 140 lakes in the Araguaia River floodplain. Total DNA was extracted, and the V4 region of the 18S rRNA gene was amplified and sequenced on the Illumina MiSeq platform. Sequences were processed using the Pimba pipeline to obtain operational taxonomic units (OTUs). A total phylogeny was constructed with all OTUs obtained, and from this phylogeny, clades belonging to the PPME groups were selected to construct a second phylogeny focused solely on PPME. Phylogenetic diversity and structure were assessed for both phylogenies using Faith’s phylogenetic diversity (PD) index and the net relatedness index (NRI). The influence of environmental and spatial variables on phylogenetic diversity and structure was analyzed through partial redundancy analysis (pRDA) and variance partitioning. Phylogenetic beta diversity was estimated using the PhyloSor index and partitioned into nestedness and turnover, while its correlation with spatial and environmental factors was assessed with a partial Mantel test. The results show that the phylogenetic diversity of the eukaryotes and photosynthetic planktonic microeukaryotes communities was significantly lower than expected by chance, indicating a non-random community structure. Most lakes showed a clustered phylogenetic pattern, suggesting that more phylogenetically related taxa co-occur more frequently. Most of the variation in phylogenetic diversity and structure was explained by space, but the spatially structured environment also had a relevant percentage of explanation. Spatial filters describing the directional connectivity between lakes had a greater explanatory power than filters using linear distances. Phylogenetic beta diversity for photosynthetic planktonic microeukaryotes was high, indicating substantial species turnover among lakes, and dissimilarity was positively correlated with environmental and spatial distances. These results suggest a significant role for environmental filtering and dispersal processes in the phylogenetic community organization and contribute to filling the knowledge gap regarding the phylogenetic diversity of planktonic microeukaryotes in the Tocantins-Araguaia River basin, underscoring the importance of considering both phylogenetic and ecological aspects to understand aquatic biodiversity.