Assessing the potential of amino acid delta C-13 and delta N-15 analysis in terrestrial and freshwater ecosystems
Assessing the potential of amino acid delta C-13 and delta N-15 analysis in terrestrial and freshwater ecosystems
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DOI：
10.1111/1365-2745.13853
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发表时间：
2022-02-23
影响因子：
5.5
通讯作者：
Newsome, Seth D.
中科院分区：
文献类型：
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作者：
Besser, Alexi C.;Smith, Emma A. Elliott;Newsome, Seth D.
1. 了解食物网的结构和动态需要准确估计生物体之间的能量流。为此通常使用大块组织碳（δ C-13）和氮（δ N-15）同位素分析；然而，这种技术的局限性可能超过其优点。单个氨基酸的同位素分析越来越多地用于追踪能量流和估计消费者营养水平。这种特定于化合物的方法的核心是必需氨基酸 (AA(ESS)) delta C-13 指纹图谱和氨基酸 (AA) delta N-15 beta 值的概念，这两个概念都尚未得到充分研究，并且在陆地和淡水生产者中很少受到限制。2。我们提供了从奇瓦瓦沙漠北部（美国新墨西哥州）两个干旱栖息地收集的 112 个陆地和淡水生产者的 AA(ESS) delta C-13 数据，以及这些样本的子集 (n = 28) 的 AA delta N-15 数据。我们通过对四个生产者组（C-3 植物、C-4 植物、CAM 植物和丝状绿藻）的异亮氨酸、亮氨酸、赖氨酸、苯丙氨酸、苏氨酸和缬氨酸的 delta C-13 值进行线性判别分析来表征 AA(ESS) delta C-13 指纹。我们通过计算 AA(ESS) 产品及其 AA 前体的 delta C-13 值之间的差异，探索了这些 AA(ESS) delta C-13 指纹背后的潜在生化机制。这使我们能够估计和比较不同生产者群体中特定 AA(ESS) 合成途径的同位素歧视。3。我们发现生产者群体之间的 AA(ESS) delta C-13 指纹近乎完美分离；在我们的多元框架内，所有组的重新分类成功率均超过 95%。我们还发现生产者群体中特定 AA(ESS) 合成途径存在不同的同位素歧视。与之前的研究相反，我们发现陆地 C-3 和 C-4 植物之间任何营养源 AA 配对的 β 值没有差异。此外，我们发现在陆地和淡水生产者中，与 Phe delta N-15 值相比，Lys delta N-15 值变化较小，并且与大块组织 delta N-15 值的相关性更密切。4。合成。我们得出结论，AA(ESS) delta C-13 指纹是淡水食物网的更高分辨率示踪剂，其中河内藻类的大量组织 delta C-13 值与陆地 C-3 植物重叠。此外，beta(Glx-Lys) 和 beta(Pro-Lys) 是包含陆地和水生资源的淡水食物网中基于 AA delta N-15 的消费者营养级估计的最佳选择。
1. Understanding the structure and dynamics of food webs requires accurate estimates of energy flow among organisms. Bulk tissue carbon (delta C-13) and nitrogen (delta N-15) isotope analysis is often used to this end; however, the limitations of this technique can outweigh the benefits. The isotope analysis of individual amino acids is being increasingly employed to trace energy flow and estimate consumer trophic level. Central to this compound-specific approach are the concepts of essential amino acid (AA(ESS)) delta C-13 fingerprinting and amino acid (AA) delta N-15 beta-values, both of which have been understudied and are poorly constrained in terrestrial and freshwater producers.2. We present AA(ESS) delta C-13 data for 112 terrestrial and freshwater producers collected from two aridland habitats in the northern Chihuahuan Desert (New Mexico, USA) and AA delta N-15 data for a subset (n = 28) of these samples. We characterized AA(ESS) delta C-13 fingerprints by performing linear discriminant analysis on the delta C-13 values of isoleucine, leucine, lysine, phenylalanine, threonine and valine for four producer groups-C-3 plants, C-4 plants, CAM plants and filamentous green algae. We explored potential biochemical mechanisms underlying these AA(ESS) delta C-13 fingerprints by calculating differences between the delta C-13 values of AA(ESS) products and their AA precursors. This allowed us to estimate and compare isotopic discrimination for specific AA(ESS) synthesis pathways across producer groups.3. We found a near-perfect separation of AA(ESS) delta C-13 fingerprints among producer groups; all groups reclassified with >95% success within our multivariate framework. We also found varied isotopic discrimination for specific AA(ESS) synthesis pathways among producer groups. Contrary to previous studies, we found no differences in beta-values between terrestrial C-3 and C-4 plants for any trophic-source AA pairing. Furthermore, we found that Lys delta N-15 values were less variable and more closely related to bulk tissue delta N-15 values than Phe delta N-15 values in terrestrial and freshwater producers.4. Synthesis. We conclude that AA(ESS) delta C-13 fingerprints are a higher resolution tracer for freshwater food webs, where instream algae have overlapping bulk tissue delta C-13 values with terrestrial C-3 plants. Additionally, beta(Glx-Lys) and beta(Pro-Lys) are the best for AA delta N-15-based consumer trophic-level estimates in freshwater food webs containing both terrestrial and aquatic resources.