Centro Investigaciones Biologicas Noroeste

Santa María de la Paz, Mexico

Centro Investigaciones Biologicas Noroeste

Santa María de la Paz, Mexico
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Blazquez M.C.,Centro Investigaciones Biologicas Noroeste | Delibes-Mateos M.,University of Porto | Delibes-Mateos M.,Institute Estudios Sociales Avanzados IESA CSIC | Vargas J.M.,University of Malaga | And 3 more authors.
Ecological Indicators | Year: 2016

Turkey Vulture (Cathartes aura) reliance on marine subsidies in coastal Baja California peninsula was quantitatively assessed by analyzing carbon and nitrogen stable isotope ratios in its feathers. Feathers were collected in two separate roosts in a small farm, a small fishing village and an uninhabited beach. We compared among them the isotopic niches of the four populations and also with those of Yellow-footed Seagull (Larus livens), Brown Pelican (Pelecanus occidentalis) and Orange-throated Whiptail lizard (Aspidoscelis hyperythra), used as reference for sympatric marine and terrestrial species. The importance of nutrients of marine origin varied among local close subpopulations, suggesting some spatial segregation. Dominant individuals would be established near predictable sources of food (human settlements), having a mixed terrestrial-marine diet influenced by local human activities (isotopic signature of feathers also indicated the role of human-fed cattle as vulture food). Subordinate individuals would be relegated to wandering along the beaches searching for washed up food, having a diet almost exclusively marine. © 2015 Elsevier Ltd. All rights reserved.


Delibes M.,CSIC - Doñana Biological Station | Blazquez M.C.,Centro Investigaciones Biologicas Noroeste | Fedriani J.M.,CSIC - Doñana Biological Station | Fedriani J.M.,Helmholtz Center for Environmental Research | And 4 more authors.
PLoS ONE | Year: 2015

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. δ13C, δ15N). 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 δ13C-δ15N 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. © 2015 Delibes et al.

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