Spatial scaling of functional and taxonomic diversity across ecosystems on an island

Spatial scale influences how we perceive, quantify, and conserve multiple biodiversity facets. Like other facets of biodiversity, functional diversity is scale-dependent and varies non-linearly with taxonomic diversity. Yet, studies commonly rely on single-scale analyses, limiting our understanding of the role of spatial scale in biodiversity patterns. Here, we assessed how spatial grain and extent modulate plant functional and taxonomic diversity of an oceanic island ecosystems. We found that grain alters the rate at which functional and taxonomic diversity accumulate across space, leading to shifts in ecosystem diversity rankings. We also found that the spatial aggregation of species and ecosystems environment likely underpin cross-grain differences in the spatial turnover of functional and taxonomic diversity, causing the grain-dependent shifts at the ecosystem level. Our study shows how ecosystem diversity and the environment shape different biodiversity facets at the island level, highlighting how anthropogenic impacts on functionally unique ecosystems may disproportionately affect island biodiversity