Several small reservoir islands consistently support higher taxonomic, phylogenetic, functional, and interaction diversity than few large ones across multiple taxa

Human-induced habitat loss and fragmentation are widespread worldwide and largely influence biodiversity distribution and conservation. Debates on conservation principles for fragmented habitats remain ongoing, among which a fundamental one is related to the SLOSS question: whether a Single Large patch (SL) Or Several Small patches (SS) with equal area host higher biodiversity. Although the intuitive SL > SS principle has commonly been applied, many studies have recently supported the SS > SL principle. However, most of these studies focus only on taxonomic diversity, overlooking other biodiversity dimensions that are crucial to ecosystem functions, such as functional, phylogenetic, and interaction diversity. Here we explored SLOSS patterns across these four biodiversity dimensions in birds, ants, and two interaction networks (avian frugivore–plant and aphid–ant networks), in a reservoir island system of eastern China. Our results revealed consistent SS > SL patterns across taxonomic, functional, phylogenetic, and interaction diversity in birds, ants, and their associated interactions. Using a new SLOSSarea index, we compared the SLOSS pattern between birds and ants. The result showed that birds, which possess greater dispersal ability, exhibited stronger extent of SS > SL patterns compared to the less mobile ants. Our research highlights that the conservation value of small islands in fragmented landscapes might extend across all facets of biodiversity.