Environmental and Spatial processes drive the phylogenetic diversity and structure of planktonic microeukaryotes revealed by metabarcoding in a tropical floodplain

Abstract

Understanding phylogenetic diversity and community patterns is fundamental to elucidating the processes that shape biodiver-sity. For this, integrating community phylogenetic approaches with advanced molecular techniques is essential for providingmore consistent estimates of community diversity and structure. Here, we investigate the phylogenetic diversity and structure ofphotosynthetic planktonic microeukaryote communities in tropical floodplain lakes using metabarcoding and tested the com-bined influence of environmental and spatial factors at broad geographical scales, including river network connectivity, on thesemetrics. We collected water samples from 140 lakes the middle Araguaia River floodplain. After filtering, DNA was extractedand amplified using primers for the 18S rRNA V4 region. To assess diversity and phylogenetic structure, we calculated Faith'sPD and Net Relatedness Index (NRI) and used variance partitioning to determine the relative influence of environmental andspatial factors (directional and nondirectional). Our results showed that PD varied significantly among lakes and was positivelycorrelated with richness. However, the observed PD was lower than expected by chance, and NRI values indicated a predom-inant pattern of phylogenetic clustering, suggesting that environmental filtering and dispersal limitations are important pro-cesses in community structuring. Variance partitioning revealed that both environmental and spatial predictors were important.Directional spatial predictors did not increase total explained variation compared to nondirectional filters, but increased theshared environmental–spatial fraction, indicating spatially structured environmental gradients. The community structure ofplanktonic microeukaryotes in the floodplain lakes of the Tocantins-Araguaia River basin is influenced by a combination ofenvironmental filters and spatial processes, highlighting the importance of conserving less degraded areas to preserve the evo-lutionary diversity of these ecosystems.