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  • A comparative analysis of metabolic rate in six Scarabaeus species (Coleoptera: Scarabaeidae) from southern Africa: further caveats when inferring adaptation.

    Author(s) : Davis, A. L. V.Chown, S. L.McGeoch, M. A.Scholtz, C. H.

    Author Affiliation : Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.

    Journal article : Journal of Insect Physiology 2000 Vol.46 No.4 pp.553-562 ref.2 pp. of

    Abstract : Alterations in VO2 or VCO2 are amongst the more polemical physiological adaptations ascribed to insects. Generally, metabolic rate is thought to be lowered in response to arid conditions, and elevated in species from cold environments compared to their more temperate relatives. However, most studies have rarely addressed the influence of both environmental factors in unison. To this end, standard metabolic rate and its temperature dependence were measured (at 4°C intervals from 16 to 32°C) in six Scarabaeus dung beetle species (three flightless, three volant) from a variety of habitats (warm, arid to cool, mesic) in southern Africa using flow-through respirometry. Mass specific VCO2 varied from 0.0158 ml g-1 h-1 at 16°C to 0.1839 ml g-1 h-1 at 32°C. The slopes of the rate temperature curves were similar for all species (Q10s of 2.14-2.84), although the intercepts differed significantly in the direction (warm arid to cool mesic): S. gariepinus < S. hippocrates < S. striatum < S. galenus < S. rusticus< S. westwoodi. General linear models were fitted to the VCO2 data with treatment temperature, wing status, mean annual rainfall and mean annual temperature as the independent variables. For all six species, the best fit model included treatment temperature and wing status only. Flightless species had significantly lower VCO2s than did winged ones. Amongst the flightless species, S. gariepinus, from the driest area, had the lowest VCO2. Among the winged species it was impossible to determine whether environmental temperature or water availability were most important in influencing VCO2; both were significant. We conclude that investigations of metabolic rate modulation, and especially metabolic cold adaptation, in insects must take both temperature and water availability into account.

    ISSN : 0022-1910

    DOI : 10.1016/S0022-1910(99)00141-9

    Record Number : 20000505096

    Language of text : English

    Language of summary : English

    Indexing terms for this abstract:

    Organism descriptor(s) : Coleoptera, Scarabaeus

    Descriptor(s) : adaptation, dung beetles, environment, environmental factors, environmental temperature, habitats, metabolism, rain, temperature

    Identifier(s) : rainfall, Scarabaeus galenus, Scarabaeus gariepinus, Scarabaeus hippocrates, Scarabaeus rusticus, Scarabaeus striatum, Scarabaeus westwoodi, subsaharan Africa

    Geographical Location(s) : Africa South of Sahara, Southern Africa

    Broader term(s) : insects, Hexapoda, arthropods, invertebrates, animals, eukaryotes, Coleoptera, Scarabaeidae, Africa South of Sahara, Africa