Multi‐scale determinants of dung beetle assemblage structure across abiotic gradients of the Kalahari–Nama Karoo ecotone, South Africa

Abstract

Aim Changing conditions across spatial gradients are primary determinants of biotic regions, local habitats, and distributional edges. We investigate how a climatic gradient and edaphic mosaic interact as multi-scale drivers of spatial patterns in scarabaeine dung beetles. The patterns are tested for congruency with ecoregion and floral boundaries over the same gradient, as responses to physical factors often differ among higher taxa.Location Southern Africa and the Nama Karoo-Kalahari ecotone, Northern Cape, South Africa.Methods Data consisted of the climatic distributions of 104 species and their abundances at 223 sites in two ecoregions/floral biomes, four bioregions, and 13 vegetation units. Factor analyses determined the biogeographical composition of the species, and regional-to local-scale patterns in species abundance structure. Hierarchical analysis of oblique factors determined the proportional contribution of spatial variance to patterns. One-way anova was used to test for significant separation of patterns along factor axes. Stepwise multiple regression was used to determine correlations of five physical attributes with species richness, ShannonWiener diversity, and factor loadings for the study sites.Results Four biogeographical influences overlap in the study region, although rank contribution declines from south-west arid through north-east savanna to widespread and south-east highland taxa. Species abundance structure comprises five subregional patterns, two centred to the north-east (Kalahari, Isolated Kalahari Dune) dominated by Kalahari influence, and three to the south-west (Nama Karoo subdivisions: Bushmanland, 'Upper', 'Stony Prieska') dominated by south-west arid influence. Kalahari deep sands are characterized especially by a warmer, moister climate, whereas the Nama Karoo mosaic of deep or stony soils is characterized especially by north-west aridity (Bushmanland), south-east cooler temperatures ('Upper'), or excessively stony soils ('Stony Prieska'). Four of the subregional patterns each comprised three localized patterns related primarily to relative stoniness, edge effects from geographical position, or incidence of rainfall. Species richness and diversity declined with decreasing rainfall and increasing stoniness.Main conclusions Climatic and edaphic factors are important multi-scale determinants of spatial patterns in dung beetle assemblage structure, with edaphic factors becoming more important at local spatial scales. The patterns are roughly congruent with the Kalahari Savanna-Nama Karoo ecotone at the floral biome or ecoregion scale, but show limited coincidence with finer-scale floral classification.

Heterogeneidade do habitat, riqueza e estrutura da assembléia de besouros rola-bostas (Scarabaeidae: Scarabaeinae) em áreas de cerrado na Chapada dos Parecis, MT

“…Esses resultados contrariaram a hipótese de que o aumento da heterogeneidade de habitat promoveria aumento da riqueza de animais (revisão: Tews et al 2004). Porém, corroboram vários trabalhos que demonstraram o efeito de variáveis ambientais na composição e estrutura da assembléia de besouros rola-bostas (Nichols et al 2007, Davis et al 2008, Gardner et al 2008, Jay-Robert et al 2008, Almeida & Louzada 2009. A relação de maior riqueza de espécies em locais com menor heterogeneidade de habitat também foi encontrada em estudos com o mesmo tipo de fi tofi sionomias em diferentes áreas do cerrado brasileiro (Milhomem et al 2003).…”

“…Formam assembléias bem defi nidas em termos taxonômicos e funcionais (Halffter & Matthews 1966, Halffter 1991) e respondem prontamente a alterações e modifi cações no habitat, sejam elas de origem antrópica, como a fragmentação (Howden & Nealis 1975, Klein 1989, Nichols et al 2007, Gardner et al 2008, ou mudança natural na estrutura da vegetação (Durães et al 2005, Davis et al 2008, Almeida & Louzada 2009). Tais mudanças podem afetar a riqueza e a composição da assembléia desses besouros (Nichols et al 2007, Gardner et al 2008, Jay-Robert et al 2008, Davis et al 1999, 2008.…”

Dung Beetle Assemblage Structure in Tswalu Kalahari Reserve: Responses to a Mosaic of Landscape Types, Vegetation Communities, and Dung Types

“…Therefore, this study examines patterns of dung beetle assemblage structure and their biogeographical composition within Tswalu Kalahari Reserve, which lies in the southwest Kalahari at the moister eastern edge of the region studied by Davis et al (2008). The owners of Tswalu support various research projects to provide inventories of the fauna and ßora and to assist in conservation management.…”

“…This includes this study (Tswalu conservation project 2009) that provides an inventory of the dung beetle fauna on different food types and determines to what extent assemblage structure on pig dung is inßuenced by factors at regional biogeographical, landscape, and local vegetation community scales of spatial organization. Its main focus is on spatial patterns that descend to a Þner-grained scale than those analyzed by Davis et al (2008).…”

How might intensification of farming influence dung beetle diversity (Coleoptera: Scarabaeidae) in Maputo Special Reserve (Mozambique)?

“…In any landscape, habitat selection by dung beetles is influenced primarily by climate, soil type, vegetation structure, and mammal dung type (Cambefort 1982;Davis 1994Davis , 1996Davis et al 2008). Of the four main influences, both vegetation and dung type availability are susceptible to short term modification (Jankielsohn et al 2001;Escobar et al 2007;Verdú et al 2007).…”