Siebers Nina, Martius Christopher, Eckhardt Kai-Uwe, Garcia Marcos V B, Leinweber Peter, Amelung Wulf
Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology, University of Bonn, Nussallee 13, 53115, Bonn, Germany.
Center of Development Research (ZEF), University of Bonn, Walter-Flex-Straße 3, 53113, Bonn, Germany.
PLoS One. 2015 Apr 24;10(4):e0123790. doi: 10.1371/journal.pone.0123790. eCollection 2015.
The impact of termites on nutrient cycling and tropical soil formation depends on their feeding habits and related material transformation. The identification of food sources, however, is difficult, because they are variable and changed by termite activity and nest construction. Here, we related the sources and alteration of organic matter in nests from seven different termite genera and feeding habits in the Terra Firme rainforests to the properties of potential food sources soil, wood, and microepiphytes. Chemical analyses comprised isotopic composition of C and N, cellulosic (CPS), non-cellulosic (NCPS), and N-containing saccharides, and molecular composition screening using pyrolysis-field ionization mass spectrometry (Py-FIMS). The isotopic analysis revealed higher soil δ13C (-27.4‰) and δ15N (6.6‰) values in nests of wood feeding Nasutitermes and Cornitermes than in wood samples (δ13C = -29.1‰, δ15N = 3.4‰), reflecting stable-isotope enrichment with organic matter alterations during or after nest construction. This result was confirmed by elevated NCPS:CPS ratios, indicating a preferential cellulose decomposition in the nests. High portions of muramic acid (MurAc) pointed to the participation of bacteria in the transformation processes. Non-metric multidimensional scaling (MDS) revealed increasing geophagy in the sequence Termes < Embiratermes < Anoplotermes and increasing xylophagy for Cornitermes < Nasutitermes., and that the nest material of Constrictotermes was similar to the microepiphytes sample, confirming the report that Constrictotermes belongs to the microepiphyte-feeders. We therewith document that nest chemistry of rainforest termites shows variations and evidence of modification by microbial processes, but nevertheless it primarily reflects the trophic niches of the constructors.
白蚁对养分循环和热带土壤形成的影响取决于它们的取食习性以及相关的物质转化过程。然而，食物来源的识别却很困难，因为其具有多变性，且会因白蚁活动和巢穴构建而发生变化。在此，我们将来自七种不同白蚁属且具有不同取食习性的亚马逊雨林地区白蚁巢穴中有机质的来源及变化，与潜在食物来源——土壤、木材和微附生植物的特性联系起来。化学分析包括碳和氮的同位素组成、纤维素（CPS）、非纤维素（NCPS）以及含氮糖类，同时还使用热解场电离质谱法（Py-FIMS）进行分子组成筛选。同位素分析显示，以木材为食的鼻白蚁属和角白蚁属巢穴中的土壤δ13C（-27.4‰）和δ15N（6.6‰）值高于木材样本（δ13C = -29.1‰，δ15N = 3.4‰），这反映出在巢穴构建期间或之后，随着有机质的变化，稳定同位素出现了富集现象。NCPS:CPS比值升高证实了这一结果，表明巢穴中纤维素分解占优。较高比例的胞壁酸（MurAc）表明细菌参与了转化过程。非度量多维标度分析（MDS）显示，在Termes < Embiratermes < Anoplotermes序列中，食土性逐渐增强，而在角白蚁属 < 鼻白蚁属序列中，食木性逐渐增强，并且Constrictotermes的巢穴材料与微附生植物样本相似，这证实了关于Constrictotermes属于微附生植物取食者的报道。我们据此证明，雨林白蚁的巢穴化学呈现出变化，并有微生物过程导致其改变的证据，但尽管如此，它主要反映了建造者的营养生态位。
