Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America.
PLoS One. 2013 Jun 28;8(6):e66505. doi: 10.1371/journal.pone.0066505. Print 2013.
We studied the plant resource use between and within populations of desert tortoise (Gopherus agassizii) across a precipitation gradient in the Sonoran Desert of Arizona. The carbon and nitrogen stable isotope values in animal tissues are a reflection of the carbon and nitrogen isotope values in diet, and consequently represent a powerful tool to study animal feeding ecology. We measured the δ(13)C and δ(15)N values in the growth rings on the shells of tortoises in different populations to characterize dietary specialization and track tortoise use of isotopically distinct C4/CAM versus C3 plant resources. Plants using C3 photosynthesis are generally more nutritious than C4 plants and these trait differences can have important growth and fitness consequences for consumers. We found that dietary specialization decreases in successively drier and less vegetated sites, and that broader population niche widths are accompanied by an increase in the dietary variability between individuals. Our results highlight how individual consumer plant resource use is bounded under a varying regime of precipitation and plant productivity, lending insight into how intra-individual dietary specialization varies over a spatial scale of environmental variability.
我们研究了亚利桑那州索诺兰沙漠降水梯度内和种群间沙漠龟（Gopherus agassizii）的植物资源利用情况。动物组织中碳和氮稳定同位素值反映了饮食中的碳和氮同位素值，因此代表了研究动物摄食生态的有力工具。我们测量了不同种群中龟壳生长环的 δ(13)C 和 δ(15)N 值，以表征饮食特化，并追踪龟类对同位素不同的 C4/CAM 与 C3 植物资源的利用。使用 C3 光合作用的植物通常比 C4 植物更有营养，这些性状差异对消费者的生长和适应性有重要影响。我们发现，随着环境变得越来越干燥和植被减少，饮食特化程度降低，而种群生态位宽度变宽伴随着个体间饮食变异性增加。我们的研究结果强调了个体消费者在不断变化的降水和植物生产力模式下植物资源利用的局限性，为了解个体饮食特化如何在空间尺度上随环境变异性而变化提供了线索。
