Biogeographic, climatic and spatial drivers differentially affect α-, β- and γ-diversities on oceanic archipelagos

Area of Science:

• Ecology
• Biogeography
• Island Biogeography

Background:

• Island biogeography traditionally focuses on single islands, overlooking their nested nature within archipelagos.
• Most islands are part of larger archipelagos, necessitating a broader analytical scope.

Purpose of the Study:

• To investigate drivers of plant diversity across entire archipelagos, not just individual islands.
• To differentiate the roles of biogeographic, climatic, and spatial factors in shaping archipelago-scale diversity.

Main Methods:

• Analyzed vascular plant species richness across 23 global archipelagos and 174 islands.
• Partitioned species diversity (gamma) into alpha, beta (nestedness and replacement) components.
• Employed multiple regressions and structural equation models to assess environmental and spatial drivers.

Main Results:

• Biogeographic and climatic factors significantly influenced alpha and gamma diversity.
• Archipelago spatial structure (number of islands, inter-island distance, area range) was key in explaining beta diversity.
• Gamma diversity was primarily driven indirectly by abiotic factors through beta diversity components.

Conclusions:

• The spatial arrangement of islands and beta diversity are critical for understanding insular plant diversity.
• A shift from single-island to archipelago-level analysis provides deeper ecological and evolutionary insights.
• The proposed framework is applicable to diverse taxa and archipelago-like systems for biodiversity research.