东太平洋中部中上层鲨鱼群落营养生态位分化

鲨鱼在大洋生态系统中占据着重要的生态地位,其作为顶级捕食者,通过下行效应直接影响生态系统的稳定.稳定同位素技术是目前研究摄食生态学强有力的手段之一,可利用碳氮稳定同位素在食物网中的特性分别指示鲨鱼的食物来源和营养级.本研究选取8种130尾采集自东太平洋中部的中上层鲨鱼,应用稳定同位素绘制其种群生态位图谱,比较不同种群间的生态地位及资源分配方式上的差异.结果表明:不同鲨鱼种群碳、氮稳定同位素比值存在显著差异;8种鲨鱼在东太平洋生态系统中的营养级为4.3~5.4,大青鲨、尖吻鲭鲨与其他6种鲨鱼存在摄食隔离,表现出独特的营养生态地位.这些结果充分证明大洋性中上层鲨鱼并非生态系统的冗余种,其营养生态位的独特性不会被其他捕食者简单地替代和弥补.     

同域分布中华鬣羚与中华斑羚时空生态位特征

为了解同域分布有蹄类在环境复杂的山地森林生境中以何种方式维持种间关系以实现稳定共存,基于物种分布模型与日活动模式分析了四川省岷山、邛崃、大相岭、小相岭和凉山五大山系同域分布中华鬣羚(Capricornis milneedwardsii)与中华斑羚(Naemorhedus griseus)的时空生态位特征。结果显示:(1)在四川省五大山系,中华鬣羚的适宜栖息地面积为28006.07 km²,占研究区总面积的26.18%,其中高适宜栖息地面积为10015.90 km²,中华斑羚的适宜栖息地面积为21073.32 km²,占研究区总面积的19.71%,其中高适宜栖息地面积为8396.22 km²;(2)中华鬣羚与中华斑羚在生境因子选择上相似性高、栖息地重叠面积大,其空间生态位重叠度指数D=0.776,I=0.949,其适宜栖息地的主要重叠区域位于岷山和邛崃山系;(3)中华鬣羚与中华斑羚的日活动节律重叠指数为0.812;(4)中华鬣羚与中华斑羚属于同域分布的资源利用型竞争物种,中华鬣羚的存在会显著影响中华斑羚的日活动节律(P=0.016);二者同域分布时都会增加其昼间活动强度,并增加活动高峰期的强度及持续时间。本研究初步分析了中华鬣羚与中华斑羚的时空生态位特征,揭示了二者在空间、时间生态位上种群共存及种间竞争的耦合关系。研究有利于深入理解同域分布动物时空生态位特征、近缘物种的共存机制及种间竞争关系,为有蹄类等珍稀野生动物种群及栖息地的保护提供科学参考。     

基于多组织稳定同位素比值的热带大西洋4种鲨鱼营养生态位分化

不同代谢速率组织间的碳、氮稳定同位素比值(δ13C和δ15N)可以反映生物不同时间尺度的摄食信息,对探讨物种间摄食、栖息地利用和营养生态位的变化具有重要的指示作用.本研究以在大西洋热带海域兼捕的大青鲨、长鳍鲭鲨、拟锥齿鲨和尖吻鲭鲨为对象,通过测定其肌肉、肝脏和血液的δ13C和δ15N值,探讨4种鲨鱼营养生态位分化.结果...     

同域分布的绿孔雀与白鹇时空生态位分化

生态位分化是同域分布的潜在竞争物种长期稳定共存的基础。研究对比一个物种与其同域分布的潜在竞争者的生态位分化,可用于指导多物种保护工作的实践。2018年6月—2019年5月利用红外相机技术对云南省玉溪市新平和峨山交界处同域分布的绿孔雀Pavo muticus和白鹇Lophura nycthemera进行野外调查,使用Wilcoxon秩和检验和非参数核密度分析旱季和雨季对植被、海拔的利用情况和日活动节律进行比较。结果表明,该地区同域分布6种雉类中,绿孔雀和白鹇的RAI指数最高(分别为0.73和0.56),为优势物种。绿孔雀活动的平均海拔高于白鹇(1 486 m±75.2 m vs. 1 390 m±71.9 m; w=8 122.5,P 0.001),且海拔生态位宽度更宽。绿孔雀对4种植被类型利用较为平均,而白鹇则倾向于利用半湿润常绿阔叶林(旱季利用率93.00%,雨季利用率77.27%)。绿孔雀的日活动节律为正常的晨昏双峰模式,白鹇却呈现出与其他研究结果不同的单峰模式,且与绿孔雀差异明显。二者在不同生态位维度上的分化可能是种间竞争的结果。建议将该地区划为以绿孔雀为主的重点雉类保护区域,未来开展更多关于野生绿孔雀的基础生态学研究。     

同域分布3种啄木鸟冬季取食的生态位差异

为了掌握黑啄木鸟、三趾啄木鸟和大斑啄木鸟的冬季取食行为特征,特别是三者之间取食生态位的差异,于2016年1月5-13日,在黑龙江省凉水国家级自然保护区以样线法结合样方法对3种啄木鸟的取食生境和取食行为进行了系统调查,收集了15个生境和行为特征变量数据。共布设45条样线,484个对照样方,收集312组啄木鸟取食数据,其中黑啄木鸟73组,三趾啄木鸟97组,大斑啄木鸟142组。多变量回归树和多分类逻辑斯谛分析结果显示,3种啄木鸟在所调查的15项特征上存在显著分异。采用基于利用-可利用方法的Bailey''s方法和双因子方差分析,分别对3种啄木鸟的生境选择和行为特征进行分析,结果显示：黑啄木鸟和三趾啄木鸟偏好在郁闭度较高的原始云、冷杉林中取食,而大斑啄木鸟则随机地在各种林型、生境中取食。黑啄木鸟、三趾啄木鸟多在树干取食,黑啄木鸟更常在倒木上取食,而大斑啄木鸟则多在树冠层取食。黑啄木鸟基本只在主干上凿洞,其他两种特别是大斑啄木鸟则可以在侧枝上取食。与黑啄木鸟和大斑啄木鸟凿洞取食昆虫不同,三趾啄木鸟多通过扒去树皮获得食物。黑啄木鸟的取食树基本为死树,单树取食时间最长,大斑啄木鸟多在活树上取食,单树取食时间最短,经常更换取食树,而三趾啄木鸟的取食树则死活参半,单树取食时间也较长。黑啄木鸟的冬季取食行为节律表现为双峰形,日出后和日落前各有一个活动高峰,其他两种则于白天持续取食。3种啄木鸟取食生境和行为生态位的差异,使它们能够更有效地利用有限的食物资源,共存于同一森林。     

大熊猫与同域动物在海拔分布上的生态位分化

大熊猫（Ailuropoda melanoleuca）是中国的特有物种,其成功放归可能受放归地气候、栖息地、同域动物等多种因素的影响。本研究在野外调查的基础上,基于生态位理论等方法,探讨了栗子坪国家级自然保护区大熊猫与其大中型同域动物的空间关系。调查结果表明,该保护区内大熊猫同域动物共20种,分别属于2纲5目,其中东洋型分布物种占优势（30%）。大熊猫同域动物分布海拔显著低于大熊猫的分布海拔（P＜0.05）,大熊猫分别与灵长目等5个目的动物在海拔分布上均存在显著的生态位分化（P＜0.001）。灵长目动物在空间分布上与大熊猫分布相异,而其他目的动物与大熊猫空间分布类似。偶蹄目动物痕迹数量占比最高（54.14 %）,而食肉目的小熊猫与大熊猫样线共同遇见率达到了43.75%。本研究结果表明,该地大熊猫同域动物较为丰富,在海拔分布上与大熊猫存在生态位分化。该研究可为圈养大熊猫的放归提供参考依据。     

基于DNA宏条形码研究四川老君山国家级自然保护区6种同域共存小型哺乳动物的食性

揭示物种共存的发生和维持机制对于群落生态学理论的发展具有重要意义,同时也是生物多样性和保护生物学研究的热点之一。生态位分化是同域分布物种实现共存的重要原因之一。为了解同域分布的多种小型哺乳动物的共存机制,本研究采用DNA宏条形码技术对四川老君山国家级自然保护区内的6种小型哺乳动物胃内容物进行分子食性分析,解析其夏季食物组成特征,并计算和比较种间食物的多样性、生态位宽度和重叠指数。结果表明:(1)鳞翅目(相对丰度:3.76%–42.33%)和双翅目(2.59%–62.63%)是6种小型哺乳动物的主要动物性食物,禾本目(0.02%–45.33%)和豆目(0.19%–38.95%)为其主要植物性食物。6种小型哺乳动物取食主要动植物性食物的相对丰度存在种间差异。(2)黄胸鼠(Rattus tanezumi)和淡灰黑齿鼩鼱(Blarinella griselda)的属水平动物性食物显著重叠(O_jk=0.63);其余物种间的营养生态位存在一定程度重叠,但在主要食物的构成和组成比例上存在明显差异;(3) 6种小型哺乳动物的动物性食物α多样性存在明显种间差异,而植物性食物α多样性...     

四川卧龙国家级自然保护区三种高山同域鸡形目鸟类的时空生态位比较

高海拔山区气候条件恶劣, 资源匮乏, 探究同域分布的近缘物种如何利用有限的资源以实现稳定共存, 对于了解高山生态系统生物多样性格局的形成和维持机制具有重要意义。鸡形目鸟类飞行能力弱, 属于典型的地栖物种, 生态位空间相对狭窄, 可能面临更高的种间竞争压力。本研究旨在比较几种同域分布的鸡形目鸟类的时空生态位, 为了解高山生态系统同域物种的共存机制提供新的研究案例。2020年4-9月, 研究人员在四川卧龙国家级自然保护区海拔3,300-4,200 m的高山区域进行了野外调查, 通过样线法和样方法对鸡形目鸟类群落优势物种绿尾虹雉(Lophophorus lhuysii)、雉鹑(Tetraophasis obscurus)和雪鹑(Lerwa lerwa)繁殖期的微生境进行调查, 使用红外相机对其活动节律进行监测, 并运用核密度估计法从微生境利用和日活动节律两个生态维度进行了种间生态位比较。结果显示, 雪鹑在微生境利用和日活动节律上均与其他两个物种存在显著差异。绿尾虹雉与雉鹑在微生境的利用上具有相似偏好; 但绿尾虹雉的早活动高峰晚于雉鹑, 晚活动高峰早于雉鹑, 表现出显著的种间日活动节律差异; 然而, 整合两个维度后, 绿尾虹雉和雉鹑的整体生态位仍然高度重叠, 没有显著分化。本研究表明高山鸡形目物种间的生态位分化体现于多个不同的生态维度, 并且不同物种之间的分化方式有所差异。在空间和时间生态位上的显著分化使雪鹑与同域物种间的竞争压力相对较小, 有利于其实现稳定共存。而绿尾虹雉与雉鹑的整体生态位高度重叠, 建议进一步对其食性开展研究, 探讨营养生态位上的潜在种间分化。     

Fatty acids differentiate consumers despite variation within prey fatty acid profiles

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Trophic niche overlap between round sardinella (Sardinella aurita) and sympatric pelagic fish species in the Western Mediterranean

The northward expansion of round sardinella (Sardinella aurita) in the Mediterranean Sea, together with declines and fluctuations in biomass and landings of European sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) observed in recent decades, may suggest potential inter‐specific competition in the pelagic domain. The coexistence of sympatric zooplanktivorous fish species might therefore be exposed in part to trophic niche overlap and competition for food. Combining visual diet characterization under the microscope with DNA metabarcoding from stomach contents of fish collected in spring results show that predation on relatively large krill is equally important for sardinella than for the other two niche overlapping species. Furthermore, an important overlap is found in their isotopic niche, especially with anchovy, using nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotopes in muscle tissue. In fact, the three fish species are able to feed effectively in the whole prey size spectrum available during the sampled season, from the smallest diatoms and copepods to the larger prey (i.e., decapods and euphausiids), including fish larvae. Moreover, effective predation upon other large prey like siphonophores, which is observed only when multi‐proxy analyses in stomach contents are applied, might also be relevant in the diet of sardinella. The overlapping diet composition in spring, together with the effective use of food resource by sardinella, can be of special interest in potential future scenarios with warmer water temperature leading to lower zooplankton and/or higher jellyfish availability, where sardinella may take advantage over other species due to its feeding plasticity.     

Trophic relationships in the pelagic zone of Mondsee,Austria

Data are presented on nutrient concentrations, phytoplankton biovolume development, zooplankton composition and population dynamics, and fish from a deep, stratifying, alpine lake (Mondsee, Austria) during a three-year period between 1982 and 1984. Development of the phytoplankton is closely related to structuring events of the physico-chemical environment. Dissolved silicate and phosphorus concentrations are critical for the summer situation. During summer algal abundance is largely affected by grazing of zooplankton, but no clear-water phase was observed at the end of the spring peak of phytoplankton.Temperature and food are factors responsible for the timing and growth of the zooplankton populations. Because of close overlap in the epilimnion, exploitative and mechanical interference competition and predation by invertebrate and vertebrate predators are the main structuring forces acting on the zooplankton community, and hence influence phytoplankton indirectly.     

Trophic niche similarities of sympatric Turdus thrushes determined by fecal contents,stable isotopes,and bipartite network approaches

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches.     

Trophic niche overlap between sympatric harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) at the southern limit of their European range (Eastern English Channel)

Sympatric harbour (Phoca vitulina) and grey seals (Halichoerus grypus) are increasingly considered potential competitors, especially since recent local declines in harbour seal numbers while grey seal numbers remained stable or increased at their European core distributions. A better understanding of the interactions between these species is critical for conservation efforts. This study aimed to identify the trophic niche overlap between harbour and grey seals at the southern limit of their European range, in the Baie de Somme (BDS, Eastern English Channel, France), where numbers of resident harbour seals and visiting grey seals are increasing exponentially. Dietary overlap was identified from scat contents using hierarchical clustering. Isotopic niche overlap was quantified using δ¹³C and δ¹⁵N isotopic values from whiskers of 18 individuals, by estimating isotopic standard ellipses with a novel hierarchical model developed in a Bayesian framework to consider both intraindividual variability and interindividual variability. Foraging areas of these individuals were identified from telemetry data. The three independent approaches provided converging results, revealing a high trophic niche overlap due to consumption of benthic flatfish. Two diet clusters were dominated by either small or large benthic flatfish; these comprised 85.5% [CI95%: 80.3%–90.2%] of harbour seal scats and 46.8% [35.1%–58.4%] of grey seal scats. The narrower isotopic niche of harbour seals was nested within that of grey seals (58.2% [22.7%–100%] overlap). Grey seals with isotopic values similar to harbour seals foraged in coastal waters close to the BDS alike harbour seals did, suggesting the niche overlap may be due to individual grey seal strategies. Our findings therefore provide the basis for potential competition between both species (foraging on benthic flatfish close to the BDS). We suggest that a continued increase in seal numbers and/or a decrease in flatfish supply in this area could cause/amplify competitive interactions and have deleterious effects on harbour seal colonies.     

Resource partitioning by sympatric pagophilic seals in Alaska: monitoring effects of climate variation with fatty acids

Four species of pagophilic phocid seals in the Western Arctic—bearded (Erignathus barbatus), ringed (Phoca hispida), ribbon (Phoca fasciata), and spotted (Phoca largha)—are particularly vulnerable to arctic warming trends. Documenting diet composition over time is one way in which the flexibility of a species, in the face of broad ecosystem changes, can be measured. Because the fatty acid (FA) composition of depot lipids has long been known to reflect diet, we analysed the FA composition of blubber samples collected from bearded (n = 30), ringed (n = 15), ribbon (n = 32) and spotted seals (n = 24). All animals were taken near Little Diomede Island in May and June 2003, providing a unique opportunity to study interspecies differences with minimal effects of spatial and temporal variation. Bearded seal FA composition was significantly different from all other seals (P < 0.001 in all cases), ringed seal FA composition was significantly different from that of both ribbon and spotted seals (P < 0.001), but ribbon and spotted seal FA compositions could not be distinguished from each other. Overall, the blubber FA compositions of ribbon, ringed and spotted seals implied diets dominated by pelagic prey. Inferences we made about current diets of bearded and ringed seals suggest that certain prey important to them in this area in the 1970s remain important today, despite notable changes in the ecosystem. We believe that blubber FA analysis will be a useful tool in assessing the response of ice-associated pinnipeds and their ecosystem to changes associated with arctic warming.     

Metabolic profiles of fish nodavirus infection in vitro: RGNNV induced and exploited cellular fatty acid synthesis for virus infection

Red‐spotted grouper nervous necrosis virus (RGNNV), the causative agent of viral nervous necrosis disease, has caused high mortality and heavy economic losses in marine aquaculture worldwide. However, changes in host cell metabolism during RGNNV infection remain largely unknown. Here, the global metabolic profiling during RGNNV infection and the roles of cellular fatty acid synthesis in RGNNV infection were investigated. As the infection progressed, 71 intracellular metabolites were significantly altered in RGNNV‐infected cells compared with mock‐infected cells. The levels of metabolites involved in amino acid biosynthesis and metabolism were significantly decreased, whereas those that correlated with fatty acid synthesis were significantly up‐regulated during RGNNV infection. Among them, tryptophan and oleic acid were assessed as the most crucial biomarkers for RGNNV infection. In addition, RGNNV infection induced the formation of lipid droplets and re‐localization of fatty acid synthase (FASN), indicating that RGNNV induced and required lipogenesis for viral infection. The exogenous addition of palmitic acid (PA) enhanced RGNNV infection, and the inhibition of FASN and acetyl‐CoA carboxylase (ACC) significantly decreased RGNNV replication. Additionally, not only inhibition of palmitoylation and phospholipid synthesis, but also destruction of fatty acid β‐oxidation significantly decreased viral replication. These data suggest that cellular fatty acid synthesis and mitochondrial β‐oxidation are essential for RGNNV to complete the viral life cycle. Thus, it has been demonstrated for the first time that RGNNV infection in vitro overtook host cell metabolism and, in that process, cellular fatty acid synthesis was an essential component for RGNNV replication.     

Discrimination of microbial diversity by fatty acid profiles of phospholipids and lipopolysaccharides in differently cultivated soils

The effects of long-term management practices on the diversity of the microbial community were examined by analyzing the composition of fatty acids (FAs) in phospholipids (PL) and lipopolysaccharides (LPS). According to the Principal Component Analysis (PCA) of total fatty acids the soils were divided in two groups: a) Black fallow soil (1) and soils cropped with potatoes (3, 4), and b) green fallow soil (2), soils cropped with wheat (5, 6), crop rotation (7) and grassland (8). The PCA for saturated FAs and for hydroxy FAs of both PL and LPS shows that the green fallow soil (2) can be distinguished from the other soils. For monounsaturated FAs the grassland soil (8) and for polyunsaturated FAs the wheat with vetch soil (6) clearly differed from the other soils. Fatty acids with biomarker quality such as 15:0 for bacteria and 18:26 for fungi were used for determining the ratio between bacteria and fungi: the black fallow soil (1) and the soil managed with crop rotation (7) contained significantly higher proportions of bacteria than the other soils. The largest proportion of the indicator fatty acid il5:0 for Gram-positive bacteria was measured in the black fallow soil (1), while the-hydroxy FAs indicative of Gram-negative bacteria most frequently occurred in manured potato cropped soil (4). Both indicator fatty acids 18:26 for fungi and cy19:0 for anaerobic bacteria had their highest concentrations in the manured potato cropped soil (4).