Rodents and palaeogenetics: New perspectives

Rodents are the most diversified mammalian order (484 extant genera including 2277 species), and they have a worldwide distribution. Palaeontological, morphological and molecular data have greatly helped to resolve their systematics and evolutionary history. However, some discrepancies remain between palaeontologists and molecular biologists. New techniques in molecular biology, and especially in palaeogenetics, allow us to have direct access to the hereditary material of extinct organisms, and they can compensate for some morphological limits. Unfortunately, few studies are dealing with rodent palaeogenetics, despite the amount of museum and fossil material available. Here, we review the major research activities in rodent palaeogenetics (phylogeny, genetic diversity, migration), and we present the promising research perspectives in this field (phylochronology, palaeoparasitology).     

Authenticated DNA from ancient wood remains

BACKGROUND: The reconstruction of biological processes and human activities during the last glacial cycle relies mainly on data from biological remains. Highly abundant tissues, such as wood, are candidates for a genetic analysis of past populations. While well-authenticated DNA has now been recovered from various fossil remains, the final 'proof' is still missing for wood, despite some promising studies. SCOPE: The goal of this study was to determine if ancient wood can be analysed routinely in studies of archaeology and palaeogenetics. An experiment was designed which included blind testing, independent replicates, extensive contamination controls and rigorous statistical tests. Ten samples of ancient wood from major European forest tree genera were analysed with plastid DNA markers. CONCLUSIONS: Authentic DNA was retrieved from wood samples up to 1,000 years of age. A new tool for real-time vegetation history and archaeology is ready to use.     

DNA条形码与动植物分类学的研究

DNA条形码在动植物分类学中的研究最近几年非常火热。这项技术在国外研究的比较多,国内的许多方面的研究还没达到国际水平。我国的动植物种类比较繁多,地区差异也较大,怎样能将这些物种准确,快速的进行分类,是众多动植物学家一直在研究的难题。针对DNA条形码研究的现状和他在动植物学中应用以及它存在的争议来进一步认识DNA条形码。     

方兴未艾的古代DNA的研究

保留在古代生物遗骸中的遗传物质DNA是一种重要的遗传资源。古代DNA的研究对于了解包括人类在内的各种生物的起源、进化和迁徙有重要意义。古代DNA的研究有其自身的特点,并且已经取得一系列重要成就。本文综述古代DNA研究的历史、方法和进展。 Abstract：DNA present in ancient samples can be recovered,amplified and analysed.It opens a new window for genetic analysis in many different disciplines,such as anthropology,archaeology,human population genetics,animal and plant evolutionary taxonomy and forensic science.In general,ancient DNA is rare in quantity,damaged in quality.To ensure the reproducibility and reliability of the results,great cares should be taken,such as various measurements against contamination and phylogenetic analysis of ancient DNA sequences.In this paper we review recovery,amplification and analysis of ancient DNA,also discuss the guidelines to ensure the authenticity of ancient DNA and the recent advances in ancient DNA study.     

Ancient DNA

In the past two decades, ancient DNA research has progressed from the retrieval of small fragments of mitochondrial DNA from a few late Holocene specimens, to large-scale studies of ancient populations, phenotypically important nuclear loci, and even whole mitochondrial genome sequences of extinct species. However, the field is still regularly marred by erroneous reports, which underestimate the extent of contamination within laboratories and samples themselves. An improved understanding of these processes and the effects of damage on ancient DNA templates has started to provide a more robust basis for research. Recent methodological advances have included the characterization of Pleistocene mammal populations and discoveries of DNA preserved in ancient sediments. Increasingly, ancient genetic information is providing a unique means to test assumptions used in evolutionary and population genetics studies to reconstruct the past. Initial results have revealed surprisingly complex population histories, and indicate that modern phylogeographic studies may give misleading impressions about even the recent evolutionary past. With the advent and uptake of appropriate methodologies, ancient DNA is now positioned to become a powerful tool in biological research and is also evolving new and unexpected uses, such as in the search for extinct or extant life in the deep biosphere and on other planets.     

DNA recovery from ancient tissues: problems and perspectives

The recovery, amplification and sequencing of nucleic acids from ancient smaples opens new possibilities in many different fields, such as anthropology, archeaology, population genetics, animal and plant evolutionary studies, and forensic medicine. The sample processing for DNA extraction and PCR amplification represents the most delicate phase of ancient DNA analysis, with a major impact on the reproducibility and reliability of the results. In this paper some extraction protocols are reviewed and discussed, with particular reference to the removal of the inhibitory substances usually present in extract from ancient tissues. The effect of contamination from extraneous DNA, a possible source of misleading results, is discussed and guidelines to detect and circumvent the problem are given.     

An integrated approach to the characterization of two autochthonous lentil (Lens culinaris) landraces of Molise (south-central Italy)

Plant biodiversity must be safeguarded because it constitutes a resource of genes that may be used, for instance, in breeding programs. Lentil (Lens culinaris Medik.) is one of the most ancient crops of the Mediterranean region. Extensive differentiation of L. culinaris over millennia has resulted in a myriad of different landraces. However, in more recent times many landraces have disappeared consequent to environmental and socioeconomic changes. To promote the survival of endangered lentil landraces, we have investigated the genetic relationship between two ancient landrace cultivated in Capracotta and Conca Casale (Molise, south-central Italy) and widely spread commercial varieties using an integrated approach consisting of studies at morphological, DNA and protein level. Seeds of these two landraces were collected from local farmers and conserved in the Molise germoplasm bank. The two local landraces were well differentiated from each other, and the Conca Casale landrace was separated from the commercial varieties at morphological, protein and DNA level. The Capracotta landrace, was well separated from the commercial varieties, except Castelluccio di Norcia, at DNA level showing a more complex and heterogeneous segregation at morphological and biochemical level. The correlation between morphological, DNA and protein data, illustrates that proteomics is a powerful tool with which to complement the analysis of biodiversity in ecotypes of a single plant species and to identify physiological and/or environmental markers.     

Legacies of the past in the present-day forest biodiversity: a review of past land-use effects on forest plant species composition and diversity

Particularly in the temperate climate zone many forests have, at some moment in their history, been used as agriculture land. Forest cover is therefore often not as stable as it might look. How forest plant communities recovered after agriculture was abandoned allows us to explore some universal questions on how dispersal and environment limit plant species abundance and distribution. All studies looking at the effects of historical land use rely on adequate land use reconstruction. A variety of tools from maps, archival studies, and interviews to field evidence and soil analyses contribute to that. They allow us to distinguish ancient from recent forests and many studies found pronounced differences in forest plant species composition between them. A considerable percentage of our forest flora is associated with ancient forests. These ancient forest plant species (AFS) all have a low colonization capacity, suggesting that dispersal in space (distance related) and time (seed bank related) limit their distribution and abundance. However recent forests generally are suitable for the recruitment of AFS. There is clear evidence that dispersal limitation is more important than recruitment limitation in the distribution of AFS. Dispersal in time, through persistent seed banks, does not play a significant role. Ancient forests are not necessary more species-rich than recent forest, but if diversity is limited to typical forest plant species then ancient forests do have the highest number of plant species, making them highly important for nature conservation. The use of molecular markers, integrated approaches and modelling are all part of the way forward in this field of historical ecology.     

Ancient genomics

The past decade has witnessed a revolution in ancient DNA (aDNA) research. Although the field''s focus was previously limited to mitochondrial DNA and a few nuclear markers, whole genome sequences from the deep past can now be retrieved. This breakthrough is tightly connected to the massive sequence throughput of next generation sequencing platforms and the ability to target short and degraded DNA molecules. Many ancient specimens previously unsuitable for DNA analyses because of extensive degradation can now successfully be used as source materials. Additionally, the analytical power obtained by increasing the number of sequence reads to billions effectively means that contamination issues that have haunted aDNA research for decades, particularly in human studies, can now be efficiently and confidently quantified. At present, whole genomes have been sequenced from ancient anatomically modern humans, archaic hominins, ancient pathogens and megafaunal species. Those have revealed important functional and phenotypic information, as well as unexpected adaptation, migration and admixture patterns. As such, the field of aDNA has entered the new era of genomics and has provided valuable information when testing specific hypotheses related to the past.     

Forensic DNA analysis for animal protection and biodiversity conservation: A review

The use of DNA analysis in forensic investigations into animal persecution and biodiversity conservation is now commonplace and crimes such as illegal collection/smuggling, poaching, and illegal trade of protected species are increasingly being investigated using DNA based evidence in many countries. Using DNA analysis, it is possible to identify the species and geographical origin (i.e. population) of a forensic sample, and to also individualise the sample with high levels of probability. Despite extensive literature in animal species, there is unfortunately a serious lack of information on plant species, with only a handful of recent studies. In this review, I detail the applications and diverse forensic investigations that have been carried out to date whilst also highlighting recent developmental studies which offer forensic potential for many species in the future.     

Ancient DNA

The review is devoted to molecular genetic studies of ancient DNA. The problems of DNA preservation and modification after cell death, as well as techniques of working with ancient DNA, including its retrieval, removal of inhibitors, PCR amplification, and phylogenetic analysis, are discussed in detail. The possibilities are considered of using ancient DNA in resolving issues of systematics and evolution of various animal taxa, population genetics of humans and rare species, taxonomic identification and paleontological reconstructions, geographic origin of populations, microbiological analysis of paleontological and archeological finds, as well as some humanitarian aspects of its use.     

Beyond ancient microbial DNA: nonnucleotidic biomolecules for paleomicrobiology

Identifying the causes of past epidemics depends on the specific detection of pathogens in buried individuals; this field of research is known as paleomicrobiology, an emerging field that has benefited from technological advances in microbiology. For almost 15 years, the detection, identification, and characterization of microbes in ancient environmental and human specimens emerged on the basis of ancient DNA (aDNA) analyses. aDNA limitations due to potential contamination by modern DNA and altered aDNA led to the development of alternative methods for the detection and characterization of nonnucleotidic biomolecules, including mycolic acids (of ancient mycobacteria) and proteins. Accordingly, immunohistochemistry, immunochromatography, and enzyme-linked immunosorbent assay techniques have been developed for the specific detection of microbes from ancient human and environmental specimens. Protein analysis by mass spectrometry, a standard for ancient animal identification, has also recently emerged as a technique for ancient mycobacteria detection, while immuno-PCR is yet another promising technique. As with aDNA, strict protocols must be enforced to ensure authenticity of the data. Here we review the analysis of nonnucleotidic biomolecules from ancient microbes and the ability of these analyses to complement aDNA analyses, which opens new opportunities for identification of ancient microbes as well as new avenues to potentially resolve controversies regarding the cause of some historical pandemics and study the coevolution of microbes and hosts.     

Ancient DNA

The review is devoted to molecular genetic studies of ancient DNA. The problems of DNA preservation and modification after cell death, as well as techniques of working with ancient DNA, including its retrieval, removal of inhibitors, PCR amplification, and phylogenetic analysis, are discussed in detail. The possibilities are considered of using ancient DNA in resolving issues of systematics and evolution of various animal taxa, population genetics of humans and rare species, taxonomic identification and paleontological reconstructions, geographic origin of populations, microbiological analysis of paleontological and archeological finds, as well as some humanitarian aspects of its use.     

环境DNA技术在地下生态学中的应用

地下生态过程是生态系统结构、功能和过程研究中最不确定的因素。由于技术和方法的限制,作为"黑箱"的地下生态系统已经成为限制生态学发展的瓶颈,也是未来生态学发展的主要方向。环境DNA技术,是指从土壤等环境样品中直接提取DNA片段,然后通过DNA测序技术来定性或定量化目标生物,以确定目标生物在生态系统中的分布及功能特征。环境DNA技术已成功用于地下生态过程的研究。目前,环境DNA技术在土壤微生物多样性及其功能方面的研究相对成熟,克服了土壤微生物研究中不能培养的问题,可以有效地分析土壤微生物的群落组成、多样性及空间分布,尤其是宏基因组学技术的发展,使得微生物生态功能方面的研究成为可能;而且,环境DNA技术已经在土壤动物生态学的研究中得到了初步应用,可快速分析土壤动物的多样性及其分布特征,更有效地鉴定出未知的或稀少的物种,鉴定土壤动物类群的幅度较宽;部分研究者通过提取分析土壤中DNA片段信息对生态系统植物多样性及植物分类进行了研究,其结果比传统的植物分类及物种多样性测定更精确,改变了以往对植物群落物种多样性模式的理解。同时,环境DNA技术克服传统根系研究方法中需要洗根、分根、只能测定单物种根系的局限,降低根系研究中细根区分的误差,并探索性地用于细根生物量的研究。主要综述了基于环境DNA技术的分子生物学方法在土壤微生物多样性及功能、土壤动物多样性、地下植物多样性及根系生态等地下生态过程研究中的应用进展。环境DNA技术对于以土壤微生物、土壤动物及地下植物根系为主体的地下生态学过程的研究具有革命性意义,并展现出良好的应用前景。可以预期,分子生物学技术与传统的生态学研究相结合将成为未来地下生态学研究的一个发展趋势。     

湖泊沉积植物古DNA的现代过程

对植被历史变化过程的研究是理解现代植被组成、分布及其对全球变化响应的基础。近年来, 随着分子古生态学的发展, 分析沉积介质中的陆生植物古DNA信号, 以研究植被及植物多样性演变的历史过程正在成为研究热点, 湖泊沉积植物古DNA已成为古植被和古生态学研究的成熟代用指标。然而与第四纪孢粉分析相比较, 湖泊沉积植物古DNA的现代过程依然不明确, 成为其进一步发展和应用的限制因素。基于此, 该文综述了湖泊沉积植物古DNA技术研究进展, 尝试阐明湖泊沉积植物古DNA的现代过程, 包括植物DNA的来源、沉积和保存过程及其影响因素, 以及植物DNA与现代植被的关系等。已有研究表明, 湖泊沉积植物古DNA主要来自湖泊周边或流域范围, 其丰度和组成除受到源植物生物量的影响外, 同样受到沉积物的搬运和沉积过程中DNA降解作用、土壤以及沉积物中颗粒的吸附过程和稀释作用等因素的影响。湖泊沉积物中植物DNA的保存则主要受到微生物活动、湖水的化学性质(电导率和pH值)、湖泊深度、沉积物组成等一系列生物与非生物因素的共同影响。湖泊沉积植物古DNA可以揭示其沉积时代的植物群落类型以及气候环境信息, 但目前并不能够用来定量重建古植被变化过程。鉴于湖泊沉积植物古DNA现代过程的复杂性, 对研究结果的解释要格外小心。与孢粉分析相比, 湖泊沉积植物古DNA研究仍处于起步阶段, 但随着分子生物技术的进步、实验设计的优化、物种条形码的扩充及参考数据库的完善等, 以DNA宏条形码和宏基因组学为主要技术手段的植物古DNA技术, 必将推动我国植物古生态研究的进一步发展。     

Ancient population genomics and the study of evolution

Recently, the study of ancient DNA (aDNA) has been greatly enhanced by the development of second-generation DNA sequencing technologies and targeted enrichment strategies. These developments have allowed the recovery of several complete ancient genomes, a result that would have been considered virtually impossible only a decade ago. Prior to these developments, aDNA research was largely focused on the recovery of short DNA sequences and their use in the study of phylogenetic relationships, molecular rates, species identification and population structure. However, it is now possible to sequence a large number of modern and ancient complete genomes from a single species and thereby study the genomic patterns of evolutionary change over time. Such a study would herald the beginnings of ancient population genomics and its use in the study of evolution. Species that are amenable to such large-scale studies warrant increased research effort. We report here progress on a population genomic study of the Adélie penguin (Pygoscelis adeliae). This species is ideally suited to ancient population genomic research because both modern and ancient samples are abundant in the permafrost conditions of Antarctica. This species will enable us to directly address many of the fundamental questions in ecology and evolution.     

Ancient DNA analysis reveals woolly rhino evolutionary relationships

With ancient DNA technology, DNA sequences have been added to the list of characters available to infer the phyletic position of extinct species in evolutionary trees. We have sequenced the entire 12S rRNA and partial cytochrome b (cyt b) genes of one 60-70,000-year-old sample, and partial 12S rRNA and cyt b sequences of two 40-45,000-year-old samples of the extinct woolly rhinoceros (Coelodonta antiquitatis). Based on these two mitochondrial markers, phylogenetic analyses show that C. antiquitatis is most closely related to one of the three extant Asian rhinoceros species, Dicerorhinus sumatrensis. Calculations based on a molecular clock suggest that the lineage leading to C. antiquitatis and D. sumatrensis diverged in the Oligocene, 21-26 MYA. Both results agree with morphological models deduced from palaeontological data. Nuclear inserts of mitochondrial DNA were identified in the ancient specimens. These data should encourage the use of nuclear DNA in future ancient DNA studies. It also further establishes that the degraded nature of ancient DNA does not completely protect ancient DNA studies based on mitochondrial data from the problems associated with nuclear inserts.     

动植物检疫在生物多样性保护中的作用

生物多样性保护不仅包括对野生物种的保护,也包含对栽培和驯化物种的遗传多样性的保护,动植物检疫在保护栽培和驯化物种的安全和防止野生物种资源外流两个方面发挥了重要作用。可以认为,动植物检疫系统是生物多样性保护中的一支生力军。文章强调,一要加强动植物检疫,减少国际贸易对生物多样性的影响;二要增强口岸把关,有效地保护我国濒危、珍稀物种资源。文中例举了过去我国濒危、珍稀生物资源破坏和流失情况,并介绍了在加强对濒危、珍稀物种进出口管理中,动植物检疫机关所起的把关作用。     

Salt drying: a low‐cost,simple and efficient method for storing plants in the field and preserving biological repositories for DNA diversity research

Although a variety of methods have been optimized for the collection and storage of plant specimens, most of these are not suited for field expeditions for a variety of logistic reasons. Drying specimens with silica gel in polyethylene bags is currently the standard for field‐sampling methods that are suitable for subsequent DNA extraction. However, silica‐gel repositories are not readily available in remote areas, and its use is not very cost‐effective for the long‐term storage of collections or in developing countries with limited research budgets. Salting is an ancient and traditional drying process that preserves food samples by dehydrating tissues and inhibiting water‐dependent cellular metabolism. We compared salt and silica‐gel drying methods with respect to dehydration rates overtime, DNA quality and polymerase chain reaction(PCR) success to assess whether dry salting can be used as an effective plant preservation method for DNA analysis. Specimens from eleven plant species covering a variety of leaf structures, leaf thicknesses and water contents were analysed. Experimental work indicated that (i) levels of dehydration in sodium chloride were usually comparable to those obtained when silica gel was used, (ii) no spoilage, fungal or bacterial growth was observed for any of the species with all drying treatments and (iii) good yields of quality genomic DNA suitable for PCR applications were obtained in the salt‐drying treatments. The preservation of plant tissues in commercial table salt appears to be a satisfactory, and versatile method that may be suitable in remote areas where cryogenic resources and silica repositories are not available.     

栽培茶树的驯化起源与传播

茶作为世界上最重要的饮品之一, 其栽培类型的驯化起源一直是人们关注的热点。本文总结了近年相关研究的进展, 讨论了存在的问题, 并对未来的研究方向提出建议。长江流域及以南地区分布有众多栽培茶树的野生近缘种, 特别集中于云南、贵州、广西等地; 一方面南方各族语言中“茶”发音的相似, 暗示了茶知识起源的单一性, 最可能起源于古代的巴蜀或云南, 另一方面遗传分析揭示栽培的茶存在多个起源中心, 即使Camellia sinensis (L.) O. Kuntze的几个栽培变种也可能起源于不同的地区; 文献记载, 茶的栽培中心曾经从西向东再向南迁移, 遗传多样性的变化也揭示了这一可能性, 但考古发现却提示最早的栽培茶可能出现在长江流域的最东部。我们推测在茶知识及栽培品种的传播过程中, 各地野生近缘植物的基因渗入栽培类型中, 或各地居民直接用当地野生茶培育出新的栽培茶类型, 从而导致遗传上的复杂性和语言上的一致性并存。茶树的祖先类型、起源地点、起源时间以及栽培品种的演变历程都还需要更为明确的证据, 未来应该以整个茶组植物为对象, 将茶文化、群体遗传学、谱系地理、人类学、气候变化、考古等多学科研究进行整合分析。