Vejříková Ivana, Eloranta Antti P, Vejřík Lukáš, Šmejkal Marek, Čech Martin, Sajdlová Zuzana, Frouzová Jaroslava, Kiljunen Mikko, Peterka Jiří
Biology Centre of the Czech Academy of Sciences, Institute of Hydrobiology, Na Sádkách 7, České Budějovice, Czech Republic.
Faculty of Science, University of South Bohemia in České Budějovice, Branišovská 31, České Budějovice, Czech Republic.
PLoS One. 2017 May 9;12(5):e0177114. doi: 10.1371/journal.pone.0177114. eCollection 2017.
Generalist species commonly have a fundamental role in ecosystems as they can integrate spatially distinct habitats and food-web compartments, as well as control the composition, abundance and behavior of organisms at different trophic levels. Generalist populations typically consist of specialized individuals, but the potential for and hence degree of individual niche variation can be largely determined by habitat complexity. We compared individual niche variation within three generalist fishes between two comparable lakes in the Czech Republic differing in macrophyte cover, i.e. macrophyte-rich Milada and macrophyte-poor Most. We tested the hypothesis that large individual niche variation among generalist fishes is facilitated by the presence of macrophytes, which provides niches and predation shelter for fish and their prey items. Based on results from stable nitrogen (δ15N) and carbon (δ13C) isotopic mixing models, perch (Perca fluviatilis L.) and rudd (Scardinius erythrophthalmus (L.)) showed larger individual variation (i.e., variance) in trophic position in Milada as compared to Most, whereas no significant between-lake differences were observed for roach (Rutilus rutilus (L.)). Contrary to our hypothesis, all the three species showed significantly lower individual variation in the relative reliance on littoral food resources in Milada than in Most. Rudd relied significantly more whereas perch and roach relied less on littoral food resources in Milada than in Most, likely due to prevalent herbivory by rudd and prevalent zooplanktivory by perch and roach in the macrophyte-rich Milada as compared to macrophyte-poor Most. Our study demonstrates how the succession of macrophyte vegetation, via its effects on the physical and biological complexity of the littoral zone and on the availability of small prey fish and zooplankton, can strongly influence individual niche variation among generalist fishes with different ontogenetic trajectories, and hence the overall food-web structures in lake ecosystems.
广适性物种在生态系统中通常具有重要的基础作用，因为它们能够整合空间上不同的栖息地和食物网组成部分，还能控制不同营养级生物的组成、丰度和行为。广适性种群通常由具有特定习性的个体组成，但个体生态位变化的潜力以及程度在很大程度上可能由栖息地复杂性决定。我们比较了捷克共和国两个具有可比性的湖泊中三种广适性鱼类的个体生态位变化，这两个湖泊的大型植物覆盖情况不同，即大型植物丰富的米拉达湖和大型植物贫乏的莫斯特湖。我们检验了这样一个假设：大型植物的存在促进了广适性鱼类个体生态位的巨大变化，大型植物为鱼类及其猎物提供了生态位和捕食庇护所。基于稳定氮（δ15N）和碳（δ13C）同位素混合模型的结果，与莫斯特湖相比，鲈鱼（Perca fluviatilis L.）和赤睛鱼（Scardinius erythrophthalmus (L.)）在米拉达湖的营养级上表现出更大的个体差异（即方差），而对于拟鲤（Rutilus rutilus (L.)），未观察到显著的湖间差异。与我们的假设相反，这三个物种在米拉达湖对沿岸食物资源的相对依赖程度上的个体差异均显著低于莫斯特湖。与大型植物贫乏 的莫斯特湖相比，在大型植物丰富的米拉达湖，赤睛鱼对沿岸食物资源的依赖程度显著更高，而鲈鱼和拟鲤对沿岸食物资源的依赖程度更低，这可能是因为在米拉达湖赤睛鱼以草食为主，而鲈鱼和拟鲤以浮游动物为食。我们的研究表明，大型植物植被的演替如何通过其对沿岸带物理和生物复杂性以及小型猎物鱼和浮游动物可利用性的影响，强烈影响具有不同个体发育轨迹的广适性鱼类之间的个体生态位变化，进而影响湖泊生态系统中的整体食物网结构。
