挑食的食虫植物？利用稳定同位素自然丰度方法，以中欧的两种陆生和两种水生狸藻科植物为研究对象，探究其对猎物营养层次的偏好。
Picky carnivorous plants? Investigating preferences for preys' trophic levels - a stable isotope natural abundance approach with two terrestrial and two aquatic Lentibulariaceae tested in Central Europe.
机构信息
Laboratory of Isotope Biogeochemistry, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany.
出版信息
Ann Bot. 2019 Jul 8;123(7):1167-1177. doi: 10.1093/aob/mcz022.
BACKGROUND AND AIMS
Stable isotope two-source linear mixing models are frequently used to calculate the nutrient-uptake efficiency of carnivorous plants from pooled prey. This study aimed to separate prey into three trophic levels as pooled prey limits statements about the contribution of a specific trophic level to the nutrition of carnivorous plants. Phytoplankton were used as an autotrophic reference for aquatic plants as the lack of suitable reference plants impedes calculation of their efficiency.
METHODS
Terrestrial (Pinguicula) and aquatic (Utricularia) carnivorous plants alongside autotrophic reference plants and potential prey from six sites in Germany and Austria were analysed for their stable isotope natural abundances (δ15N, δ13C). A two-source linear mixing model was applied to calculate the nutrient-uptake efficiency of carnivorous plants from pooled prey. Prey preferences were determined using a Bayesian inference isotope mixing model.
KEY RESULTS
Phytophagous prey represented the main contribution to the nutrition of Pinguicula (approx. 55 %), while higher trophic levels contributed a smaller amount (diverse approx. 27 %, zoophagous approx. 17 %). As well as around 48 % nitrogen, a small proportion of carbon (approx. 9 %) from prey was recovered in the tissue of plants. Aquatic Utricularia australis received 29 % and U. minor 21 % nitrogen from zooplankton when applying phytoplankton as the autotrophic reference.
CONCLUSIONS
The separation of prey animals into trophic levels revealed a major nutritional contribution of lower trophic level prey (phytophagous) for temperate Pinguicula species. Naturally, prey of higher trophic levels (diverse, zoophagous) are rarer, resulting in a smaller chance of being captured. Phytoplankton represents an adequate autotrophic reference for aquatic systems to estimate the contribution of zooplankton-derived nitrogen to the tissue of carnivorous plants. The autonomous firing of Utricularia bladders results in the additional capture of phytoplankton, calling for new aquatic references to determine the nutritional importance of phytoplankton for aquatic carnivorous plants.
背景与目的
稳定同位素双源线性混合模型常用于从混合猎物中计算肉食性植物的养分吸收效率。本研究旨在将猎物分为三个营养级，因为混合猎物限制了对特定营养级对肉食性植物营养贡献的表述。由于缺乏合适的参考植物，藻类被用作水生植物的自养参考，以计算其效率。
方法
本研究对来自德国和奥地利六个地点的陆生（貉藻属）和水生（狸藻属）肉食性植物以及自养参考植物和潜在猎物的稳定同位素自然丰度（δ15N、δ13C）进行了分析。应用双源线性混合模型从混合猎物中计算肉食性植物的养分吸收效率。使用贝叶斯推断同位素混合模型确定猎物偏好。
主要结果
植食性猎物是貉藻属植物营养的主要来源（约 55%），而较高的营养级贡献较小（杂食性约 27%，肉食性约 17%）。除了约 48%的氮，植物组织中还回收了一小部分来自猎物的碳（约 9%）。当以藻类作为自养参考时，水生狸藻属植物 U. australis 从浮游动物中获得 29%的氮和 U. minor 21%的氮。
结论
将猎物动物按营养级分离，揭示了较低营养级猎物（植食性）对温带貉藻属物种的主要营养贡献。自然地，较高营养级的猎物（杂食性、肉食性）更为稀少，因此被捕食的机会更小。藻类是水生系统中估算浮游动物衍生氮对肉食性植物组织贡献的合适自养参考。狸藻属植物的自主喷射会额外捕获藻类，因此需要新的水生参考来确定藻类对水生肉食性植物的营养重要性。
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