Species richness – Energy relationships and dung beetle diversity across an aridity and trophic resource gradient

Abstract

_____________________________________________________________________________________________Understanding factors that drive species richness and turnover across ecological gradients is important for insect conservation planning. To this end, we studied species richness -energy relationships and regional versus local factors that influence dung beetle diversity in game reserves along an aridity and trophic resource gradient in the Botswana Kalahari. Dung beetle species richness, alpha diversity, and abundance declined with increasing aridity from northeast to southwest and differed significantly between dung types (pig, elephant, cattle, sheep) and carrion (chicken livers). Patterns of between-study area species richness on ruminant dung (cattle, sheep) differed to other bait types. Patterns of species richness between bait types in two southwest study areas differed from those in four areas to the northeast. Regional species turnover between study areas was higher than local turnover between bait types. Patterns of southwest to northeast species loss showed greater consistency than northeast to southwest losses from larger assemblages. Towards the southwest, similarity to northeast assemblages declined steeply as beta diversity increased. High beta diversity and low similarity at gradsect extremes resulted from two groups of species assemblages showing either northeast or southwest biogeographical centres. The findings are consistent with the energy hypothesis that indicates insect species richness in lower latitudes is indirectly limited by declining water variables, which drive reduced food resources (lower energy availability) represented, here, by restriction of large mammals dropping large dung types to the northeast and dominance of pellet dropping mammals in the arid southwest Kalahari. The influence of theoretical causal mechanisms is discussed.

Effects of grazing intensity and the use of veterinary medical products on dung beetle biodiversity in the sub-mountainous landscape of Central Italy

“…For example, Tshikae, Davis & Scholtz (2013) explicitly tested the species–energy relationship for dung beetles across an arid and trophic resource gradient in Botswana. Their results showed that the species richness, diversity and biomass of the dung beetle diminish with a decrease in available (trophic) energy.…”

Edaphic and climatic history has driven current dung beetle species pool and assemblage structure across a transition zone in central South Africa

“…It is known that deep sands support more dung beetle species than finer‐grained soils (Davis, ) but this observation has to be weighed against effects of different climatic combinations in the Nama Karoo. Such declines across ecological gradients from apparently more favourable to potentially harsher ecological conditions are frequently observed in insect assemblages (Pérez‐Sánchez, Lattke & Viloria, ; Tshikae, Davis & Scholtz, ) although there are exceptions possibly related to asymmetric variability and interaction between factors such as aridity, soil type and/or temperature (Pfeiffer, Chimedregzen & Ulykpan, ; Delsinne et al ., ).…”

Peer Review #2 of "Spatial and temporal variations of aridity shape dung beetle assemblages towards the Sahara desert (v0.1)"

“…Hortal, Lobo & Martin-Piera, 2001;Tshikae, Davis & Scholtz, 2013b, c Manuscript to be reviewed however inexistent or even reversed in other organisms and/or systems (Polis, 1991;Polis et al, 1997;Delsinne et al, 2010;Andersen et al 2015). Water availability may determine species richness through two main mechanisms: physiological constraints (Chown et al, 2011) -thus following the water-energy hypothesis (Hawkins et al, 2003a); and resource availability (Nichols et al, 2009;Tshikae et al, 2013c) -following the species-energy hypothesis (Wright, 1983).…”