Fine‐scale heterogeneity in beetle assemblages under co‐occurring Eucalyptus in the same subgenus

Abstract

Aim Insect biodiversity is often positively associated with habitat heterogeneity. However, this relationship depends on spatial scale, with most studies focused on differences between habitats at large scales with a variety of forest tree species. We examined fine‐scale heterogeneity in ground‐dwelling beetle assemblages under co‐occurring trees in the same subgenus: Eucalyptus melliodora A. Cunn. ex Schauer and E. blakelyi Maiden (Myrtaceae). Location Critically endangered grassy woodland near Canberra, south‐eastern Australia. Methods We used pitfall traps and Tullgren funnels to sample ground‐dwelling beetles from the litter environment under 47 trees, and examined differences in diversity and composition at spatial scales ranging from 100 to 1000 m. Results Beetle assemblages under the two tree species had distinctive differences in diversity and composition. We found that E. melliodora supported a higher richness and abundance of beetles, but had higher compositional similarity among samples. In contrast, E. blakelyi had a lower abundance and species richness of beetles, but more variability in species composition among samples. Main conclusions Our study shows that heterogeneity in litter habitat under co‐occurring and closely related eucalypt species can influence beetle assemblages at spatial scales of just hundreds of metres. The differential contribution to fine‐scale alpha and beta diversity by each eucalypt can be exploited for conservation purposes by ensuring an appropriate mix of the two species in the temperate woodlands where they co‐occur. This would help not only to maximize biodiversity at landscape scales, but also to maintain heterogeneity in species richness, trophic function and biomass at fine spatial scales.

The spatial scaling of beta diversity

“…By contrast, most management interventions at larger scales, such as tree plantings, may enhance only the perceived 'quality' of habitat for a subset of vertebrate species at landscape scales (Cunningham et al, 2007). This may have limited or no effect on some groups of organisms that perceive and respond to plant composition at finer spatial scales (Tylianakis et al, 2006;Barton et al, 2010). This is not to say that management intervention at landscape scales is unimportant.…”

Environmental and spatial drivers of spider diversity at contrasting microhabitats

“…For the eucalypt trees in our study area, this includes large amounts of leaf litter (McElhinny et al 2010), which is known to affect spider assemblages (Uetz 1979), and litter-dwelling arthropods more broadly (Niemel€ a et al 1996;Barton et al 2010). Each of the microhabitats is characterized by distinct set of abiotic conditions and candidate prey species.…”

“…Manipulation of key structural features of habitat, such as trees (Stenchly et al 2011) or woody debris (Castro & Wise 2010;Barton et al 2011), can provide a tractable approach to the management of habitat to benefit biodiversity. Further, these structures provide distinct microhabitats for a variety of taxa (Harmon et al 1986), yet how they contribute to assemblage turnover across landscapes is only just becoming apparent (Barton et al 2009(Barton et al , 2010. For example, it is well established that coarse woody debris and individual trees provide localized hotspots of ecological function in landscapes by retaining soil moisture and nutrient content (McElhinny et al 2010;Goldin & Hutchinson 2013).…”

“…To date, few studies of ground-dwelling spiders have been conducted in Australian eucalypt woodlands (but see Martin & Major 2001;Harris et al 2003;Major et al 2006;Recher & Majer 2006). This allows for a comparative approach to the analysis of spider diversity, and can potentially reveal how the spatial and environmental structuring of assemblage diversity and composition at fine scales contributes to large-scale diversity (Barton et al 2009(Barton et al , 2010. We sampled spider assemblages from three distinct microhabitats: (i) in open grassland, (ii) near logs and (iii) under trees.…”

The influence of native versus exotic streetscape vegetation on the spatial distribution of birds in suburbs and reserves

“…For example, eucalypt species of the Monocalyptus subgenera, for example, stringybarks and scribbly gums, have lower foliage nutrient levels, poorer invertebrate assemblages and are less likely to produce hollows compared with species of the Symphyomyrtus subgenera, for example, boxes and red gums (McElhinny et al, 2006). Further, even within the same subgenus, different eucalypt species can differ significantly in the richness and abundance of insects they support (Barton et al, 2010). The importance of multi-species plantings should also be addressed in future research.…”