title: Isotopic niche variation in a higher trophic level ectotherm: highlighting the role of succulent plants in desert food webs.
abstract: Stable isotope analysis of animal tissues allows description of isotopic niches, whose axes in an n-dimensional space are the isotopic ratios, compared to a standard, of different isotope systems (e.g. δ(13)C, δ(15)N). Isotopic niches are informative about where an animal, population or species lives and about what it consumes. Here we describe inter- and intrapopulation isotopic niche (bidimensional δ(13)C-δ(15)N space) of the Orange-throated whiptail (Aspidoscelis hyperythra), an arthropodivorous small lizard, in ten localities of Baja California Sur (Mexico). These localities range from extreme arid to subtropical conditions. Between 13 and 20 individuals were sampled at each locality and 1 cm of tail-tip was collected for isotope analysis. As expected, interpopulation niche width variation was much larger than intrapopulation one. Besides, isotopic variation was not related to age, sex or individual size of lizards. This suggests geographic variation of the isotopic niche was related to changes in the basal resources that fuel the trophic web at each locality. The position of Bayesian isotope ellipses in the δ-space indicated that whiptails in more arid localities were enriched in 13C, suggesting most of the carbon they ingested came from CAM succulent plants (cacti, agaves) and in minor degree in C4 grasses. Contrarily, whiptails in subtropical areas were depleted in 13C, as they received more carbon from C3 scrubs and trees. Localities closer to sea-level tended to be enriched in 15N, but a clear influence of marine subsidies was detected only at individual level. The study contributes to identify the origin and pathways through which energy flows across the trophic webs of North American deserts.
authors.affiliation: Department of Conservation Biology, Estación Biológica de Doñana, CSIC, Avda. Américo Vespucio s/n, 41092, Seville, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Delibes
authors.affiliation: Centro Investigaciones Biológicas Noroeste, Avda. Politécnico Nacional 195, 23090, La Paz, B.C.S., Mexico.
authors.forename: Ma Carmen
authors.initials: MC
authors.lastname: Blazquez
authors.affiliation: Department of Conservation Biology, Estación Biológica de Doñana, CSIC, Avda. Américo Vespucio s/n, 41092, Seville, Spain; Department of Ecological Modelling, Helmholtz Centre for Environmental Research GmbH-UFZ, Permoserstrasse 15, 04318, Leipzig, Germany; Technical University of Lisbon, Institute of Agronomy, Centre for Applied Ecology, Tapada da Ajuda, 1349-017, Lisboa, Portugal.
authors.forename: Jose Maria
authors.initials: JM
authors.lastname: Fedriani
authors.affiliation: Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Camino del Jueves s/n, 18100, Armilla, Granada, Spain.
authors.forename: Arsenio
authors.initials: A
authors.lastname: Granados
authors.affiliation: Department of Conservation Biology, Estación Biológica de Doñana, CSIC, Avda. Américo Vespucio s/n, 41092, Seville, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Soriano
authors.affiliation: Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Camino del Jueves s/n, 18100, Armilla, Granada, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Delgado
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D005260:Female; D020387:Food Chain; D008116:Lizards / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis; D013623:Tail / Q000737:chemistry / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002244:Carbon; D009584:Nitrogen