Ground‐dwelling beetle assemblages in the northern Cape Floristic Region: Patterns, correlates and implications

Abstract

Recent studies have both shown and predicted that global climate change will have a substantial influence on biodiversity.This is true especially of a global biodiversity hotspot, the Cape Floristic Region. Although the effects of predicted changes have been widely assessed for plants, little is known about how insect diversity in the region might be affected. In particular, patterns in and the correlates of diversity in the region are poorly understood, and therefore the likely affects of a changing abiotic environment on this significant group of organisms are not clear.Therefore, we investigate patterns in, and correlates of, epigaeic beetle (Tenebrionidae and Carabidae) diversity in one of the most climate change-sensitive areas in the Cape Floristic Region, the Cederberg. In particular, we determine whether epigaeic beetle assemblage structure differs between the main vegetation types in the Cederberg (Strandveld, Mountain Fynbos and Succulent Karoo), how restricted these beetles are to specific vegetation types, and which environmental variables might be associated with site-related differences in beetle richness and abundance. Sampling was undertaken during October 2002 and 2003 across an altitudinal gradient ranging from sea level (Lambert's Bay) to approximately 2000 m above sea level (Sneeukop, Cederberg) and down again to 500 m above sea level (Wupperthal) using pitfall traps. The environmental correlates of abundance and species density in the epigaeic beetles were similar to those identified previously for ants across the transect, with both taxa being positively related to several temperature variables. Several species showed habitat specificity and fidelity, and clear distinctions existed between the vegetation types across the transect. A larger proportion of the variance in tenebrionid species density was explained by environmental variables and spatial factors than for carabids. The most likely explanation for this difference is that the correlates might well reflect collinear historical processes, rather than a causal relationship between contemporary environmental variables and species density. If this is the case, it suggests that caution should be exercised when interpreting environmental correlates of species density, and making climate change predictions based on these correlates.

Temporal and spatial patterns of tenebrionid beetle diversity in NW Patagonia, Argentina

“…An example of this are N. rotundipennis, Emmallodera obesa costata Kulzer, Nyctopetus argentinus Freude and Scotobius alaticollis Kulzer that have become common insects in scrublands and open and dry forests (Mazía et al, 2006;Sackmann et al, 2008). A similar pattern has been described for the Cape floristic region, where the eastward decline in species richness of tenebrionid assemblages reflects movement away from the southern end of the south-west African centre of tenebrionid endemism and diversity (Botes et al, 2007).…”

“…These adaptations are mostly influenced by temperature; however other factors such as vegetation type and soil topography may also affect their distribution and abundance (e.g. Ayal and Merkl, 1994;Botes et al, 2007;Krasnov and Ayal, 1995). Tenebrionid assemblages usually show spatial and temporal change in relation to variation in the environmental conditions (e.g.…”

“…Tenebrionid assemblages usually show spatial and temporal change in relation to variation in the environmental conditions (e.g. Ayal and Merkl, 1994;Botes et al, 2007;de los Santos et al, 2000;Krasnov and Ayal, 1995).…”

Community structure of ground beetles (Coleoptera: Carabidae) along an altitudinal gradient on Mt. Sobaeksan, Korea

“…In general, two types of species richness patterns are frequently observed with increasing altitude: a monotonicdecreased due to resource limitation and thermal constraints (Fiedler and Beck, 2008) or a hump-shaped (Colwell and Lees, 2000) pattern due to the combined effects of many environmental variables and associated processes promoting the co-occurrence of many species (Lomolino, 2001). Although not assessed in a statistical framework, ground beetle assemblages have been reported to show a monotonic-decreased in species richness with increasing altitude (Greenslade, 1968;Meyer and Thaler, 1995;Butterfield, 1996;Gobbi et al, 2007), but some studies reported a hump-shaped pattern for altitudes from 1000 to 2600 m (Suttiprapan et al, 2006) or a hump-shaped pattern with an increase at the summit area from 0 to 1900 m (Botes et al, 2007). However, these previous studies provided limited information; only the dominant vegetation or temperatures at the altitudes investigated were reported.…”

“…they show habitat specificity and fidelity (Thiele, 1977;Lövei and Sunderland, 1996;Rainio and Niemelä, 2003;Pearce and Venier, 2006;Botes et al, 2007). These ecological characteristics of ground beetles make them ideal organisms for study to assess biodiversity and habitat characteristics along environmental gradients.…”