title: Stable isotope analysis of diet confirms niche separation of two sympatric species of Namib Desert lizard.
abstract: We used stable isotopes of carbon and nitrogen to study the trophic niche of two species of insectivorous lizards, the Husab sand lizard Pedioplanis husabensis and Bradfield's Namib day gecko living sympatrically in the Namib Desert. We measured the δ(13) C and δ(15) N ratios in lizard blood tissues with different turnover times (whole blood, red blood cells and plasma) to investigate lizard diet in different seasons. We also measured the δ(13) C and δ(15) N ratios in available arthropod prey and plant tissues on the site, to identify the avenues of nutrient movement between lizards and their prey. Through the use of stable isotope mixing models, we found that the two lizard species relied on a largely non-overlapping but seasonally variable array of arthropods: P. husabensis primarily fed on termites, beetles and wasps, while R. bradfieldi fed mainly on ants, wasps and hemipterans. Nutrients originating from C3 plants were proportionally higher for R. bradfieldi than for P. husabensis during autumn and late autumn/early winter, although not summer. Contrary to the few available data estimating the trophic transfer of nutrients in ectotherms in mixed C3 and C4 /crassulacean acid metabolism (CAM) plant landscapes, we found that our lizard species primarily acquired nutrients that originated from C4 /CAM plants. This work adds an important dimension to the general lack of studies using stable isotope analyses to estimate lizard niche partitioning and resource use.
authors.affiliation: Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Ian W
authors.initials: IW
authors.lastname: Murray
authors.affiliation: Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.|Biology Department, Whitman College, Walla Walla, Washington, USA.
authors.forename: Hilary M
authors.initials: HM
authors.lastname: Lease
authors.affiliation: Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Robyn S
authors.initials: RS
authors.lastname: Hetem
authors.affiliation: Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Duncan
authors.initials: D
authors.lastname: Mitchell
authors.affiliation: Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fuller
authors.affiliation: iThemba Laboratories, Gauteng, South Africa.|Stable Isotope Laboratory, Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
authors.forename: Stephan
authors.initials: S
authors.lastname: Woodborne
mesh_terms: D000818:Animals; D001181:Arthropods / Q000737:chemistry; D002247:Carbon Isotopes / Q000097:blood; D004032:Diet / Q000662:veterinary; D020387:Food Chain; D008116:Lizards / Q000097:blood / Q000502:physiology*; D009276:Namibia; D009587:Nitrogen Isotopes / Q000097:blood; D010944:Plants / Q000737:chemistry; D012621:Seasons; D061350:Sympatry
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes
keywords: Namib Desert; Pedioplanis; Rhoptropus; niche partitioning; stable isotopes