4 research outputs found
Rift Valley fever vector diversity and impact of meteorological and environmental factors on Culex pipiens dynamics in the Okavango Delta, Botswana
Trophic Associations of a Dung Beetle Assemblage (Scarabaeidae: Scarabaeinae) in a Woodland Savanna of Botswana
Species richness – Energy relationships and dung beetle diversity across an aridity and trophic resource gradient
Understanding factors that drive species richness and turnover across ecological gradients is important
for insect conservation planning. To this end, we studied species richness e 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.The GEF-Small Grant Programme and the University of Pretoriahttp:// www.elsevier.com/locate/actoechb2013ab201
Dung beetle assemblage structure across the aridity and trophic resource gradient of the Botswana Kalahari: patterns and drivers at regional and local scales
Understanding pattern and process at both regional and local scales is important for conservation planning although such knowledge of insects is frequently lacking. To assess patterns along a regional gradient of increasing aridity and diminishing food resources in the Botswana Kalahari, Scarabaeine dung beetles were sampled quantitatively using four dung types at three local sites in six regional areas. At regional scale, factor analysis of species abundance extracted a maximum of six factors, each dominated by a single area. Therefore, the statistical significance of regional spatial variation far outweighed that of dung type association. At local scale, six factor analyses of species abundance extracted from four to six factors. The importance of local dung type associations was relatively high but diminished with increasing local spatial heterogeneity. At regional scale, hierarchical analysis of oblique factors divided assemblages into unique local and shared regional components. Primary extended factors accounted for 40–50 % of unique local faunal composition in five out of six areas. Two secondary extended factors showed either high shared proportional contribution to regional assemblage structure in the northeast with a steep decline to the southwest, or an opposite trend. Their point of intersection was consistent with a boundary zone between mesic northeast and arid southwest faunal components in the central Kalahari. Despite some inconsistencies in rank position between regression methods, rainfall, temperature, and mammal density/diversity were the strongest influences on regional patterns defined by secondary factors. Patterns are discussed according to conservation and changes in land usage around reserves.The GEF-Small Grant Programme and the University of Pretoriahttp://www.springerlink.com/content/100177/hb2013ab201