Conservation prioritization of macrobenthic communities in subtropical bays: Insights from multidimensional beta diversity and community assembly processes

Understanding the spatial patterns of biodiversity and the underlying mechanisms of community assembly provides a scientific basis for the conservation and management of coastal ecosystems. Using macrobenthic communities from three subtropical bays and adjacent open waters in China, we assessed taxonomic, functional, and phylogenetic beta diversity (βsor) and partitioned it into turnover (βsim) and nestedness (βnes) components. We employed variation partitioning (VPA), local contributions to beta diversity (LCBD), species contributions to beta diversity (SCBD), neutral community modeling (NCM), and the modified stochasticity ratio (MST) to identify key drivers of community differentiation and the relative roles of deterministic versus stochastic assembly processes. Results showed that βsim dominated βsor across all diversity dimensions. Spatial factors generally outperformed environmental variables in explaining beta diversity. Bay areas exhibited significantly higher ecological uniqueness in functional and phylogenetic composition, with deterministic processes dominating their community assembly, whereas stochastic processes prevailed in open waters. This study highlights that bay communities, shaped by environmental filtering, harbor unique functional trait combinations and evolutionary histories and should be assigned higher conservation priority. Integrating multidimensional beta diversity with community assembly mechanisms provides a quantifiable scientific framework for guiding conservation planning and marine protected area design in coastal ecosystems.