Where are the bees? Sharp functional transition in bee assemblages at Australian cool temperate rainforest margins.

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Temperate rainforests in eastern Australia persist as isolated refugia within fire-prone sclerophyll landscapes, typically buffered by ecotonal vegetation. Understanding how insect communities transition across these boundaries is critical for predicting the cascading effects of changing fire regimes. We quantified flower-visiting insect assemblages across contiguous rainforest, ecotone, and sclerophyll habitats at four high-altitude sites along the Great Dividing Range using coloured pan traps during spring and early summer 2020. From a balanced subset of 3,059 individuals representing 100 species, species richness and Shannon diversity increased significantly from rainforest to sclerophyll (P < 0.001) while total abundance did not differ. The sharpest functional transition was for bees: zero were recorded across 36 rainforest samples, whereas sclerophyll supported 21 species and the ecotone just four. Flies dominated all habitats but comprised 96% of rainforest individuals compared with 89% in sclerophyll. Overall community composition was strongly influenced by site and season, with habitat effects spatially variable (habitat x site interaction, P = 0.036) and most pronounced in late season. Rainforest boundaries therefore represent a sharp functional transition for pollinators, despite more subtle and context-dependent shifts in overall community structure. The complete absence of bees from rainforest implies that pollination services for bee-dependent plant species are reliant on adjacent vegetation. Degradation of ecotonal and sclerophyll habitats through severe fires that destroy structural complexity and nesting substrates and may disrupt the pollinator connectivity between these habitats.