Abstract
Clearing of dry forests globally creates edges between remnant forest and open anthropogenic habitats. We used flight intercept traps to evaluate how forest beetle communities are influenced by distance from such edges, together with vertical height, spatial location, and local vegetation structure, in an urbanising region (Brisbane, Australia). Species composition (but not total abundance or richness) differed greatly between ground and canopy. Species composition also varied strongly among sites at both ground and canopy levels, but almost all other significant effects occurred only at ground level, where: species richness declined from edge to interior; composition differed between positions near edges (<10 m) and interiors (> 50 m); high local canopy cover was associated with greater total abundance and richness and differing composition; and greater distances to the city centre were associated with increased total abundances and altered composition. Analyses of individual indicator species associated with this variation enabled further biological interpretations. A global literature synthesis showed that most spatially well-replicated studies of edge effects on ground-level beetles within forest fragments have likewise found that positions within tens of metres from edges with open anthropogenic habitats had increased species richness and different compositions from forest interior sites, with fewer effects on abundance. Accordingly, negative edge effects will not prevent relatively small compact fragments (if >10–20 ha) from supporting forest-like beetle communities, although indirect consequences of habitat degradation remain a threat. Retention of multiple spatially scattered forest areas will also be important in conserving forest-dependent beetles, given high levels of between-site diversity.
Highlights
Habitat destruction is a major contributor to biodiversity loss [1]
We evaluate how beetle (Coleoptera) communities within dry subtropical forest are influenced by distance from edges with open anthropogenic habitat, together with the additional factors of vertical height, spatial location, and local vegetation structure, in an urbanising region
Accumulation curves for each edge distance showed a progressive decrease in ground level species richness from edge to interior, but no such edge effect at canopy level (Fig 2)
Summary
Habitat destruction is a major contributor to biodiversity loss [1]. Forest cover has been reduced and fragmented by clearing, which has greatly increased the area covered by new forms of open anthropogenic habitat such as agriculture, pasture and suburbs. Conceptual frameworks have focused on the conservation implications for edge-avoiding species, especially when high ratios of edge to core habitat area in small or linear forest patches cause large reductions in effective habitat area, and when edge effects penetrate deeply into forest [2, 8, 9]. In such cases, retention of large habitat patches will be a high conservation priority [8, 10], since the edge-avoiding species would be expected to disappear from an equivalent total forest area that was more widely distributed among smaller patches, leading to regional declines in insect diversity
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