Value of ecological infrastructure diversity in the maintenance of spider assemblages: A case study of Mediterranean vineyard agroecosystems

Within agricultural landscapes, ecological infrastructures like hedges, grass strips or wildflower strips, can be essential for the provision of ecosystem services, and their role in maintaining and promoting functional biodiversity has been widely demonstrated in temperate zones. However, although the Mediterranean basin is considered to be a biodiversity hotspot, there is a lack of information about the role played there by these elements in biodiversity conservation. Spiders are generalist predators that are considered important components of biodiversity in vineyard ecosystems, where they can play a prominent role in the natural control of pest populations. Nevertheless, the influence that ecological infrastructures have on driving spider assemblages in Mediterranean vineyard agroecosystems is practically unknown. In a study conducted in an area exclusively devoted to traditional vineyard crops (La Rioja, northern Spain), we analyzed spider assemblages across four types of linear ecological infrastructures differing in their structural diversity: woodland hedges, rosaceous hedges, grass strips and flower strips. Spider assemblages were examined across three levels of organization (taxon, guild and body-size group). Taxonomic composition was different among infrastructures, as was guild composition and the distribution of body sizes. Abundance and richness of spiders were higher in more structurally diverse infrastructures. The response to habitat type differed among guilds but, overall, higher densities of spiders from different guilds were found in hedges. Body-size groups had a more balanced distribution in strips and hedges with higher levels of structural diversity. Our results suggest that it is crucial to preserve varied typologies of ecological infrastructures, with an optimal level of complexity and heterogeneity, to maintain diversified assemblages of these important biocontrol agents within Mediterranean vineyard agroecosystems.