Steinitz Ronnie, Lemm Jeffrey M, Pasachnik Stesha A, Kurle Carolyn M
Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, CA, 92093-0116, USA.
San Diego Zoo Institute for Conservation Research, Behavioral Ecology Division, Escondido, CA, 92027-7000, USA.
Rapid Commun Mass Spectrom. 2016 Jan 15;30(1):9-21. doi: 10.1002/rcm.7410.
Stable isotope analysis is a powerful tool for reconstructing trophic interactions to better understand drivers of community ecology. Taxon-specific stable isotope discrimination factors contribute to the best use of this tool. We determined the first Δ(13)C and Δ(15)N values for Rock Iguanas (Cyclura spp.) to better understand isotopic fractionation and estimate wild reptile foraging ecology.
The Δ(13)C and Δ(15)N values between diet and skin, blood, and scat were determined from juvenile and adult iguanas held for 1 year on a known diet. We measured relationships between iguana discrimination factors and size/age and quantified effects of lipid extraction and acid treatment on stable isotope values from iguana tissues. Isotopic and elemental compositions were determined by Dumas combustion using an elemental analyzer coupled to an isotope ratio mass spectrometer using standards of known composition.
The Δ(13)C and Δ(15)N values ranged from -2.5 to +6.5‰ and +2.2 to +7.5‰, respectively, with some differences among tissues and between juveniles and adults. The Δ(13)C values from blood and skin differed among species, but not the Δ(15)N values. The Δ(13)C values from blood and skin and Δ(15)N values from blood were positively correlated with size/age. The Δ(13)C values from scat were negatively correlated with size (not age). Treatment with HCl (scat) and lipid extraction (skin) did not affect the isotope values.
These results should aid in the understanding of processes driving stable carbon and nitrogen isotope discrimination factors in reptiles. We provide estimates of Δ(13)C and Δ(15)N values and linear relationships between iguana size/age and discrimination factors for the best interpretation of wild reptile foraging ecology.
稳定同位素分析是重建营养级相互作用以更好理解群落生态学驱动因素的有力工具。特定分类群的稳定同位素分馏因子有助于该工具的最佳使用。我们确定了岩鬣蜥（Cyclura属）的首个δ¹³C和δ¹⁵N值，以更好地理解同位素分馏并估计野生爬行动物的觅食生态学。
从在已知饮食条件下饲养1年的幼年和成年鬣蜥中，测定饮食与皮肤、血液和粪便之间的δ¹³C和δ¹⁵N值。我们测量了鬣蜥分馏因子与大小/年龄之间的关系，并量化了脂质提取和酸处理对鬣蜥组织稳定同位素值的影响。使用元素分析仪通过杜马斯燃烧法测定同位素和元素组成，并使用已知组成的标准品与同位素比率质谱仪联用。
δ¹³C和δ¹⁵N值分别在-2.5至+6.5‰和+2.2至+7.5‰之间，不同组织之间以及幼年和成年个体之间存在一些差异。血液和皮肤的δ¹³C值因物种而异，但δ¹⁵N值没有差异。血液和皮肤的δ¹³C值以及血液的δ¹⁵N值与大小/年龄呈正相关。粪便的δ¹³C值与大小（而非年龄）呈负相关。用HCl处理（粪便）和脂质提取（皮肤）不影响同位素值。
这些结果应有助于理解驱动爬行动物稳定碳和氮同位素分馏因子的过程。我们提供了δ¹³C和δ¹⁵N值的估计以及鬣蜥大小/年龄与分馏因子之间的线性关系，以最佳解释野生爬行动物的觅食生态学。
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