Factors Affecting Seed Germination and Seedling Establishment of Fen-Meadow Species

Availability of seeds and provision of “safe sites” for seedling recruitment are essential for successful restoration of seminatural grassland communities. Inability to provide species‐specific conditions for seedling recruitment appears to be a major factor limiting establishment of fen‐meadow species on restoration sites. This contention was tested in the field for both germination and establishment conditions for a selection of fen‐meadow species. A Cirsio‐Molinietum fen meadow and an agriculturally semi‐improved species‐poor grass dominated rush pasture were used. Seeds of Carex ovalis, Cirsium dissectum, Molinia caerulea, Succisa pratensis, and Holcus lanatus were sown onto treatments comprising either irrigation or no irrigation, presence or absence of existing vegetation canopy, and presence or absence of soil disturbance. Germination of all except H. lanatus was higher in the fen meadow than in the rush pasture. The fen‐meadow site was less susceptible to drought, provided more light to the seed environment, and showed a stronger day–night variation in relative humidity compared with the rush pasture. All the fen‐meadow species responded strongly to the experimental treatments, whereas H. lanatus showed only a small response. Soil disturbance was the major factor that increased germination. Removal of the vegetation canopy improved germination only in S. pratensis. Conditions affecting survival of seedlings were different from those affecting seed germination. Seedling survival was greater on the fen‐meadow site than on the rush pasture. Canopy presence was the major factor that reduced seedling survival. Few seedlings survived in the presence of the rush pasture canopy. Irrigation and soil disturbance were of minor importance for seedling survival on both sites. Safe sites for seed germination and seedling establishment of fen‐meadow species existed on the fen meadow even without soil disturbance and gap creation. Safe sites for seedling recruitment were not present in the rush pasture. The need for species‐specific definition of safe site characteristics at the two stages of seedling recruitment (i.e., for seed germination and for seedling survival) was demonstrated. The implications of these findings for restoration of seminatural grasslands are discussed.     

Automated Quantification of Hematopoietic Cell – Stromal Cell Interactions in Histological Images of Undecalcified Bone

Confocal microscopy is the method of choice for the analysis of localization of multiple cell types within complex tissues such as the bone marrow. However, the analysis and quantification of cellular localization is difficult, as in many cases it relies on manual counting, thus bearing the risk of introducing a rater-dependent bias and reducing interrater reliability. Moreover, it is often difficult to judge whether the co-localization between two cells results from random positioning, especially when cell types differ strongly in the frequency of their occurrence. Here, a method for unbiased quantification of cellular co-localization in the bone marrow is introduced. The protocol describes the sample preparation used to obtain histological sections of whole murine long bones including the bone marrow, as well as the staining protocol and the acquisition of high-resolution images. An analysis workflow spanning from the recognition of hematopoietic and non-hematopoietic cell types in 2-dimensional (2D) bone marrow images to the quantification of the direct contacts between those cells is presented. This also includes a neighborhood analysis, to obtain information about the cellular microenvironment surrounding a certain cell type. In order to evaluate whether co-localization of two cell types is the mere result of random cell positioning or reflects preferential associations between the cells, a simulation tool which is suitable for testing this hypothesis in the case of hematopoietic as well as stromal cells, is used. This approach is not limited to the bone marrow, and can be extended to other tissues to permit reproducible, quantitative analysis of histological data.     

Weak phylogenetic effects on ecological niches of Sylvia warblers

To understand the evolution of ecological niches it is important to know whether niche evolution is constrained by phylogeny. We approached this question for Sylvia warblers by testing if closely related species are more similar in 20 ecologically relevant morphological traits than distantly related species. Phylogenetic relatedness was quantified using a molecular phylogeny based on the mitochondrial cytochrome b gene. By Principal Component Analysis (PCA) two major niche axes were extracted. We tested the individual ecomorphological traits and the positions of the species on the PCA axes for phylogenetic effects using Mantel tests. The results demonstrated small but significant phylogenetic effects only for the length of the middle toe, a trait probably correlated with locomotion. In general, however, phylogenetic effects were very weak. This suggests that ecological niches in passerine birds have the potential to evolve rapidly and are not subject to major phylogenetic constraints.     

黔中喀斯特地区马尾松群落主要物种种间联结、生态位及群落稳定性特征

研究群落内主要物种的种间联结、生态位宽度与重叠及群落稳定性,能够了解群落结构及优势物种的资源利用习性,对森林经营管理和植被恢复与重建具有重要的意义。基于黔中喀斯特山地贵阳市乌当区2021年7月的马尾松群落调查数据,采用方差比率法(VR)、χ²检验、Spearman秩相关检验、Levins生态位宽度指数、Pianka生态位重叠指数和M.Godron稳定性等方法,对该群落主要物种的种间联结、生态位及群落稳定性进行分析。结果表明:该群落乔木层、灌木层和草本层主要物种间的总体关联性均呈不显著正关联,66.67%-80.95%的种对均无显著关联,种间关联较松散且相关性较弱,各物种间呈独立分布格局;马尾松的重要值和生态位宽度最大(为20.78),与伴生物种间均存在生态位重叠;群落整体及各垂直层次的稳定性均远离20/80,处于不稳定状态。因此,在喀斯特山地生态恢复和保护工作中,应优先选择生态习性和生物学特性相近的物种,合理调整植被组成以维持种间平衡,提高群落稳定性。     

马缨杜鹃根系微生物群落结构及其变化

【目的】为了解野生马缨杜鹃根系微生物的群落结构特征,比较百里杜鹃内马缨杜鹃根际土壤、根表及根内3个生态位微生物群落组成差异,探究杜鹃根系生态位之间、变化菌属间的相互关系,以期为今后杜鹃根系微生物研究提供具有参考价值的数据。【方法】对百里杜鹃内野生马缨杜鹃根系微生物16S rRNA V4区和ITS1区进行高通量测序,比较分析根际土壤、根表及根内微生物群落多样性及组成差异;并基于共变化网络分析进一步探究差异菌属间的相互关系。【结果】马缨杜鹃根系不同的生态位之间,微生物群落结构存在差异,其中以根际土壤与根表、根内差异更为显著,且细菌群落差异小于真菌群落。且从根际-根表-根内,马缨杜鹃根系细菌α-多样性显著下降。马缨杜鹃根系微生物分布于41细菌门和6个真菌门。优势细菌门为变形菌门(Proteobacteria,39.64%±0.08,69.47%±0.12,77.34%±0.07)、酸杆菌门(Acidobacteria,34.10%±0.11,11.03%±0.04,9.18%±0.04)以及放线菌门(Actinobacteria,10.19%±0.03,8.70%±0.02,7.08%±0.01),它们占整体细菌群落总丰度的80%以上。同时8个细菌菌门的相对丰度在根际土壤、根表和根内间显著变化,且它们的相对丰度占细菌群落总丰度的75%以上。真菌主要分布于接合菌门(Zygomycota)、担子菌门(Basidiomycota)和子囊菌门(Ascomycota),它们占整体菌群的99%以上。马缨杜鹃根系存在589个属的细菌,390个属的真菌,从根际-根表-根内,其中25个细菌属和10个真菌属的相对丰度发生显著变化。马缨杜鹃根系微生物群落共变化网络分析表明:在马缨杜鹃根系不同生态位间,除Waitea外,包括枝孢菌属(Cladosporium)、拟盘多毛孢属(Pestalotiopsis)等在内的8个差异真菌菌属均与细菌菌属显著相关,它们相互作用调控微生物群落结构的变化。Bryobacter、Nocardia、Rhizomicrobium和Telmatobacter等核心菌属对马缨杜鹃根系微生物群落共变化网络的变化具有十分重要的调控作用。【结论】百里杜鹃地区马缨杜鹃根际土壤、根表以及根内3个生态位间,微生物群落组成存在差异;而造成微生物组成存在差异这一结果,可能与马缨杜鹃根系密切相关。同时,共变化网络分析揭示出马缨杜鹃根系生态位之间,细菌和真菌彼此间互作。     

烟台近海浮游动物优势种空间生态位研究

根据2018年春、夏季烟台近海海域的调查资料,以浮游动物优势种(类)为研究对象,运用Levins公式和Pianka指数分析了浮游动物优势种(类)的生态位宽度和生态位重叠程度,采用冗余分析(RDA)研究了影响浮游动物优势种(类)空间生态位分化的主要因素。研究结果表明,浮游幼虫和桡足类是烟台近海浮游动物群落结构的主要组成群体,春、夏季浮游动物优势种(类)更替率为73.33%。依据烟台近海浮游动物优势种(类)的生态位宽度值,可将其划分为广生态位、中生态位和窄生态位三大类群,广生态位种类为浮游动物优势种(类)的主要构成群体,春季代表种类有短角长腹剑水蚤(Oithona brevicornis)、拟长腹剑水蚤(Oithona similis)等,夏季代表种类有小拟哲水蚤(Paracalanus parvus)、克式纺锤水蚤(Acartia clausi)等。生态位重叠指数与物种分布的环境位点的重合情况密切相关,广生态位种类之间的生态位重叠程度要高于窄生态位种类与其他种类之间的生态位重叠程度。RDA分析表明,春季影响浮游动物优势种(类)空间生态位分化的主要因素为海水温度、盐度和无机氮(DIN),夏...     

Climatic factors influencing triatomine occurrence in Central-West Brazil

We estimated the geographic distributions of triatomine species in Central-West Region of Brazil (CW) and analysed the climatic factors influencing their occurrence. A total of 3,396 records of 27 triatomine species were analysed. Using the maximum entropy method, ecological niche models were produced for eight species occurring in at least 20 municipalities based on 13 climatic variables and elevation. Triatoma sordida and Rhodnius neglectus were the species with the broadest geographic distributions in CW Brazil. The Cerrado areas in the state of Goiás were found to be more suitable for the occurrence of synanthropic triatomines than the Amazon forest areas in the northern part of the state of Mato Grosso. The variable that best explains the evaluated models is temperature seasonality. The results indicate that almost the entire region presents climatic conditions that are appropriate for at least one triatomine species. Therefore, it is recommended that entomological surveillance be reinforced in CW Brazil.