Intraspecific trait variation and whole‐plant economics spectrum drive the abundance distributions of woody plants in island communities

Abstract Understanding the coexistence of common and uncommon species is crucial for exploring community assembly processes and facilitating biodiversity conservation across spatial and temporal scales. This study extends the Equilibrium Theory of Island Biogeography (ETIB) to explore how island geographical variables shape the whole‐plant economics spectrum, emphasizing the relationship between intraspecific trait variation (ITV) and species abundance. We quantified ITV within plant communities on 10 land‐bridge islands and investigated its relationship with species abundance. Using generalized linear mixed models (GLMMs), we examined the effects of island geographical variables (island area, isolation, and distance to forest edge) and abundance on ITV patterns. With a rarefaction method, we identified a positive correlation between species abundance and ITV. Common species were predominantly located at the core positions of the community‐wide trait distribution, whereas uncommon species were more often positioned at its margins. Island area, isolation, distance to forest edge, species abundance, and their interactions all significantly influenced ITV patterns. Common species on smaller, more isolated islands and along island edges displayed traits indicative of slow‐growth and resource‐conservative (stress‐tolerant) strategies, while uncommon species on larger, less isolated islands and in island interiors exhibited traits consistent with fast‐growth and resource‐acquisitive strategies. Synthesis . Higher ITV may enhance the tolerance of common species in heterogeneous island habitats, supporting their persistence despite environmental variability. Conversely, lower ITV and smaller population sizes increase the vulnerability of uncommon species to extinction due to habitat loss and fragmentation. Extending ETIB to include plant trait economics provides novel insights into how island geography shapes species trait strategies and community dynamics, offering valuable insights for biodiversity conservation in fragmented landscapes.