Maintaining remnant vegetation along with plant diversification in vineyards is optimal for conserving arthropods in an agricultural mosaic in a biodiversity-rich region

Edges between adjacent biotopes may hinder or promote spillover of arthropods, influencing their distribution across landscapes. An understanding of spillover between natural and production areas enables management of edge effects for optimal biodiversity conservation. We assessed arthropod assemblages across vineyard-fynbos edges in the Cape Floristic Region of South Africa, where biodiversity-rich fynbos often borders vineyards. Species richness, assemblage composition, and compartmentalised beta-diversity (species turnover and nestedness) were assessed for three vegetation layers (ground level, lower vegetation, and upper vegetation) to determine bidirectional spillover. Species were also categorised according to biotope affiliation (crop-associated, fynbos-associated, or ubiquitous), based on habitat fidelity. We assessed how species richness of each biotope affiliation was influenced by environmental and management variables. Our main interest was biotope-specific variables which may enhance or impede spillover by influencing arthropods affiliated with the opposite biotope. Arthropod species richness did not differ along vineyard-fynbos transects for ground and lower vegetation layers but was lower in the upper vineyard vegetation compared to fynbos. Arthropod assemblages were distinct between biotopes for upper and lower vegetation but were similar on the soil surface and showed lower nestedness differences, indicating greater spillover by ground-level arthropods. In vineyards, no variables influenced fynbos-associated species, although herbaceous vegetation cover promoted ubiquitous arthropod species richness. Spillover between the biotopes was limited, and no drivers could be identified that promote spillover into vineyards, yet both biotopes supported diverse and distinct arthropod assemblages. Therefore, conservation of natural fynbos patches alongside sensitively managed vineyards is feasible for harmonising biodiversity conservation and viticulture.