Phylogenetic diversity and community assembly in a naturally fragmented system

We sought to assess effects of fragmentation and quantify the contribution of ecological processes to community assembly by measuring species richness, phylogenetic, and phenotypic diversity of species found in local and regional plant communities. Specifically, our fragmented system is Craters of the Moon National Monument and Preserve, Idaho, USA. CRMO is characterized by vegetated islands, kipukas, that are isolated in a matrix of lava. We used floristic surveys of vascular plants in 19 kipukas to create a local species list to compare traditional dispersion metrics, mean pairwise distance, and mean nearest taxon distance (MPD and MNTD), to a regional species list with phenotypic and phylogenetic data. We combined phylogenetic and functional trait data in a novel machine‐learning model selection approach, Community Assembly Model Inference (CAMI), to infer probability associated with different models of community assembly given the data. Finally, we used linear regression to explore whether the geography of kipukas explained estimated support for community assembly models. Using traditional metrics of MPD and MNTD neutral processes received the most support when comparing kipuka species to regional species. Individually no kipukas showed significant support for overdispersion. Rather, five kipukas showed significant support for phylogenetic clustering using MPD and two kipukas using MNTD. Using CAMI, we inferred neutral and filtering models structured the kipuka plant community for our trait of interest. Finally, we found as species richness in kipukas increases, model support for competition decreases and lower elevation kipukas show more support for habitat filtering models. While traditional phylogenetic community approaches suggest neutral assembly dynamics, recently developed approaches utilizing machine learning and model choice revealed joint influences of assembly processes to form the kipuka plant communities. Understanding ecological processes at play in naturally fragmented systems will aid in guiding our understanding of how fragmentation impacts future changes in landscapes.     

高黎贡山南段种子植物区系的特有现象

高黎贡山南段是全球生物多样性研究热点地区之一,迄今计有野生种子植物192科878属2 807种.这一区域不仅植物的种类丰富,而且特有现象较为显著.其中东亚特有科8个、中国特有属17个、中国特有种1 085个、云南特有种305个、高黎贡山南段特有种82个.特殊地质历史和生态环境,使得高黎贡山南段既保留了许多古老特有成分,又孕育了许多新生特有成分.     

北京地区手参内生真菌的区系组成分析

手参Gymnadenia conopsea是一种地生兰科植物,也是中国传统中药材之一。研究以ITS1为目标序列,应用 Illumina MiSeq高通量测序技术对北京地区松山和百花山的手参内生真菌区系组成进行测定分析。结果表明,从手参的根中获得有效序列50 420条,209个可操作分类单元（OTUs）,分属于3门9纲28目54科,包括盘菌纲Pezizomycetes（3个OTU）、伞菌纲Agaricomycetes（21个OTU）、锤舌菌纲Leotiomycetes（18个OTU）、粪壳菌纲Sordariomycetes（51个OTU）、接合菌纲Zygomycetes（18个OTU）、银耳纲Tremellomycetes（19个OTU）、散囊菌纲Eurotiomycetes（22个OTU）、酵母纲Saccharomycetes（8个OTU）、座囊菌纲Dothideomycetes（14个OTU）。其中,百花山手参根中内生真菌优势类群是鸡油菌目Cantharellales（38.62%）和柔膜菌目Helotiales（24.64%）真菌;松山手参的优势内生菌类群是盘菌目Pezizales（66.19%）和鸡油菌目Cantharellales（29.75%）真菌。这些结果利于系统了解手参根部内生真菌区系组成以及优势内生真菌类群,为今后开展相关内生真菌在手参人工繁育中的应用奠定了基础。     

构树: 一种新型木本模式植物

构树(Broussonetia papyrifera)属于桑科(Moraceae)构属(Broussonetia)多年生乔木, 是一种具有重要价值的多功能树种。构树叶可做蛋白饲料, 树皮是造纸的优质原料, 根、茎、叶、果实及种子均可入药。构树具有分布广和适应性强的特性, 其有性繁殖和无性繁殖迅速, 雌雄异株, 严格异交, 世代周期短, 后代种子数量大, 株型多样, 基因组紧凑, 易转化, 表型性状和遗传多样性丰富, 可以作为研究木质素和纤维素合成、黄酮类和氮代谢、异形叶形成、植物性别分化机制以及植物抗性和环境适应性进化等植物学领域重大关键问题的模式材料。该文重点阐述构树作为模式植物的主要依据, 简要介绍构树的研究进展, 并对今后构树的研究框架进行初步设计。     

The effect of light and seed mass on seed germination of common herbaceous species from the eastern Qinghai‐Tibet Plateau

Smaller seeds might encounter more severe selective pressure than larger ones because they have fewer food reserves and are more easily buried; thus, seed mass can be considered to be directly related to the effect of light on germination. To investigate the effect of light on seed germination and associated seed mass variation within a whole plant community, we compiled germination data for common herbaceous species from an alpine meadow on the eastern Qinghai‐Tibet plateau. The results showed the following. (i) Light had a general positive effect on seed germination. Under light, the proportion of species with lower germinability was decreased, mean germination percentage was increased by 20% and the speed of germination was doubled. (ii) Irrespective of light environment, species with medium‐sized seeds (seed mass ranging from 0.11 to 0.5 mg) had higher germination percentage and speed when compared with species within the largest seed mass group. (iii) The germination of smaller‐seeded species was more dependent on light stimulation than larger‐seeded ones. In darkness, the species within the smallest seed mass group had the lowest percentage and speed of germination; however, under light, the species within the largest seed mass group had the lowest percentage and speed of germination. Our results suggested that the germination characteristics and especially seeds’ response to light among species in the alpine meadow might be an adaptation to natural selective pressure.     

外马廊山岛植被特性与植物多样性

该研究对无居民海岛舟山外马廊山岛进行初步踏勘,了解该岛植被特征与植物多样性,探讨海岛植被与大陆植被的差异性,并对海岛植物的主要植物组成、生活型结构、地理成分、群落类型以及多样性和相似性进行了分析。结果表明:外马廊山岛面积小,共有33科51属55种植物,植物种类偏少,留存有普陀狗哇花,滨柃,厚叶石斑木等具有滨海特色植物,具有开发潜力。外马廊山岛热带成分较为明显,与附近地区较为相似。岛上群落优势种或建群种的科为山茶科,大戟科,松科等,与大陆的常绿阔叶林的优势种或建群种的优势科如樟科,金缕梅科,壳斗科,山茶科等不大相同。岛上植物主要以高位芽植物为主(58.18%),但较大陆常绿阔叶林的高位芽植物比例要低。外马廊山岛植物群落结构简单,植物多样性相对较低,物种丰富较低,主要原因在于生态适应性和演替过程的差异,岛上植物群落演替至稳定群落还需要相当一段时间。外来种比例占9.09%,外来种如黑松和红鸡竹能形成群落或在群落中具有较为明显的优势,并可能会造成一定的生态干扰。     

不同基质中水鳖对共存的穗花狐尾藻和金鱼藻的影响

研究设置了营养水平不同的3种基质,在有或无浮水植物水鳖共存的情况下,混合种植营养吸收方式不同的两种沉水植物（仅从水中吸收营养的金鱼藻和从水和基质都能吸收营养的穗花狐尾藻）,探讨在不同的基质中浮水植物对沉水植物的影响。结果显示:实验中水鳖的存在均未对共存的两种沉水植物的生长产生抑制作用。当水鳖覆盖水面时,与无根的金鱼藻竞争光照和水体营养,促使其增加分枝数和茎长,并增加叶生物量的分配,最终导致水鳖的共存促进了金鱼藻的生物量积累。但与金鱼藻不同,有根的穗花狐尾藻可通过基质吸收营养,与共存的水鳖之间只存在光照竞争,使穗花狐尾藻仅以改变植株形态来适应浮水植物的表层覆盖,生物量积累并未发生显著变化。与沙处理相比,水鳖在营养水平较高的泥处理和泥沙混合处理中生长更旺盛,基质没有显著影响沉水植物的生物量和分株数。因此,在退化湿地生态系统中恢复水生植物时,为了提高群落的物种多样性,可以将沉水植物与少量的浮水植物组合配置,少量的浮水植物不会对沉水植物的生长带来负面影响。     

环状RNA的生物特征及其在植物中的研究进展

环状RNA(circular RNA,circRNA)是真核细胞中广泛存在的一类由3′末端和5′末端共价结合形成的环状非编码RNA(non-coding RNA,ncRNA)。越来越多的研究表明,circRNA具有种类丰富、结构稳定、序列保守以及细胞或组织特异性表达等特点。circRNA具有很多潜在的功能,例如作为天然小RNA(microRNA,miRNA)海绵体吸附并调控miRNA的活性,与转录调控元件结合或与蛋白互作调控基因的转录等。目前关于circRNA的研究多集中在动物和人体中,在植物中的研究还较少,仅在水稻(Oryza sativa)、拟南芥(Arabidopsis thaliana)、小麦(Triticum aestivum)、猕猴桃(Actinidia chinensis)、番茄(Solanum lycopersicum)和大豆(Glycine max)等中鉴定到了circRNA的存在,并且其作用机理尚不清楚。该文主要针对circRNA的分类、形成机制、分子特征、相关研究方法以及在植物中的主要研究进展进行综述,并对目前植物circRNA研究中存在的问题进行了分析总结。     

Long‐term responses of leaf litter decomposition to temperature,litter quality and litter mixing in plateau wetlands

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