Biogeodynamic controls on Caribbean community structure during the formation of the Isthmus of Panama 

The progressive restriction of seaways between the Caribbean and Pacific during the formation of the Isthmus of Panama fundamentally reorganized ocean circulation, biogeochemical cycling, and marine ecosystem structure across the tropical Americas. This tectonically driven reorganization provides a natural experiment for examining how long-term Earth system processes influence the structure, stability, and resilience of biological communities. The Bocas del Toro region of Caribbean Panama preserves a rich fossil record that captures ecological responses to these coupled physical and environmental changes.This study examines temporal variation in marine community composition and functional trait structure using fossil assemblages from four marine formations: Cayo Agua, Escudo de Veraguas, Old Bank, and Isla Colón, spanning approximately 6.0 to 0.43 Ma. The analyses integrate multiple taxonomic groups, including bivalves, gastropods, bryozoans, corals, and fishes, enabling comparison of ecological responses among organisms that differ in life habit, mobility, feeding strategy, tiering, and ecological function. By incorporating multiple clades with contrasting ecologies, this approach allows assessment of whether community change reflects reorganization within broadly conserved functional roles or more fundamental shifts in ecosystem structure.Community dynamics are quantified using a combination of model-based ordination, taxon-specific response analyses, and functional diversity metrics applied within a stratigraphic framework. These methods explicitly account for variation in sampling intensity and taxonomic richness, allowing ecological patterns to be distinguished from sampling effects. Biological patterns are evaluated alongside sedimentological and geochemical records to place community dynamics within their environmental context. Environmental–trait and environmental–taxon relationships are evaluated within a generalized linear latent variable modeling (GLLVM) framework to assess how changes in physical conditions, sedimentary processes, and geochemical variability influence community reorganization before, during, and after the formation of the Isthmus of Panama. Comparisons among contemporaneous formations allow local ecological responses to be distinguished from regionally coherent environmental signals.Overall, this study aims to clarify how long-term tectonic and oceanographic reorganization shapes marine ecosystem structure and stability, providing a stratigraphically grounded perspective on the links between Earth system processes and ecological dynamics over geological timescales.