There’s theory, and then there is collecting actual evidence to support a theory, which tends to be messy. In this case, the theory is that more complex habitats should support more diversity. They didn’t at least in this study of insects and spiders in Sydney.

Habitat complexity does not affect arthropod community composition in roadside greenspaces

Urban greenspaces including remnant patches of vegetation, backyard gardens and public parks provide important habitat for wildlife conservation. Maintaining and enhancing the conservation value of these spaces requires both an understanding of the biodiversity they support, and the factors, including habitat traits, influencing species occurrence. Roadside greenspaces, including road verges and median strips are often overlooked in current greenspace biodiversity studies. We quantified arthropod community assemblages in roadside and public park greenspaces, and determined if habitat complexity was an important trait influencing species composition in these areas. Using pitfall traps, we sampled ground dwelling arthropods along five major roads in the greater Sydney Region and in public parks. Whilst roadside greenspaces (road verges and median strips) and public parks supported significantly different arthropod assemblages, habitat complexity had no impact on community assemblage and neither factor affected the assemblage of key arthropods taxa including ants, beetles and spiders. Additionally, in public parks but not road side greenspaces we found an effect of habitat complexity on arthropod abundance; arthropods were more abundant in high complexity park sites. Our results highlight the unique arthropod community assemblage supported by roadside greenspaces, and suggest management practices like increasing habitat complexity may be important in some but not all urban greenspace types.