Evolutionary and ecological consequences of interspecific hybridization in cladocerans

The evolutionary process of interspecific hybridization in cladocerans is reviewed based on ecological and population genetic data. The evolutionary consequences of hybridization, biogeographic patterns and fitness comparisons are analyzed within the conceptual framework of theories on hybridization. Among species of theD. longispina complex no interpopulational transition zones (hybrid zones) have been detected, but rather patchy distributions of hybrids and parentals have been found. Hybrids occur across broad geographic ranges and can be more abundant than parental species. Due to asexual reproduction (ameiotic parthenogenesis), hybrid breakdown can be avoided, and hybrids can even (temporarily) combine advantageous traits of both parental species. Evolutionary consequences may arise from repeated backcrossing, which in some cases results in introgression and patterns of reticulate evolution.Those forms which possess in some considerable degree the character of species, but which are so closely similar to some other forms, or are so closely linked to them by intermediate gradations, that naturalists do not like to rank them as distinct species, are in several respects the most important to us (Charles Robert Darwin 1859)     

Integrative taxonomic analysis reveals a new species of Leptobrachium (Anura: Megophryidae) from north-eastern Cambodia and central Vietnam

ABSTRACT

Species boundaries within the red-eyed Leptobrachium of southern Indochina have been uncertain. Leptobrachium pullum and L. mouhoti from upper and lower elevations, respectively, of the Langbian Plateau of southern Vietnam and eastern Cambodia differ in body size but have relatively low interspecific mitochondrial DNA divergence, leading to speculation that these might represent a single species with an elevational cline in body size. The recent discovery of an allopatric high-elevation population of red-eyed Leptobrachium on the Kon Tum Plateau (= Central Highlands) of north-eastern Cambodia and central Vietnam has been referred to both species, and to a putatively undescribed species. We examine variation in morphology of adults and tadpoles, mitochondrial DNA, 11 nuclear genes and advertisement calls, and show corroborating lines of evidence for the existence of three species of red-eyed Leptobrachium in southern Indochina. Although the three species are reciprocally monophyletic in mitochondrial DNA, their shallow mitochondrial DNA divergences are not mirrored by morphology, advertisement calls, or – in part – nuclear DNA, and probably reflect past mitochondrial introgression rather than recent speciation. The Central Highlands taxon is described herein as a new species.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:CE6650AF-D9FB-40F4-8A2E-9B4E23AAC205     

自然杂交对植物物种生存进化的影响

自然杂交是一个常见现象,人类活动正加速自然杂交的发生,人类干扰导致的非自然的杂交过程对物种的生存、进化产生许多负面影响,本文根据文献对近年来自然杂交方面的研究进行了综述。自然杂交不仅影响着物种的生存、进化,也对物种的保护问题带来许多理论上与实践上的挑战。杂交与遗传渗入有利于提高物种的遗传多样性,为物种的进化提供原材料。遗传渗入有利于增加物种的适应性变异,甚至导致新的生态型、新物种的产生。但另一方面当小种群与大种群发生杂交时,小种群很易受遗传同化的影响而灭绝。自然杂交对生物学物种概念提出了挑战,自然杂交往往模糊种间边界,形成分类学及系统发育研究中的困难类群。自然杂交能通过强化种间生殖隔离机制来促进类群间的进化趋异,也能导致种间生殖隔离机制的崩溃,引起物种的融合而降低生物多样性。文章认为在当前生物入侵、物种灭绝加速的情况下,人们需要关注在什么条件下隔离机制被打破导致杂交的发生、遗传渗入形成机制以及如何采取有效措施防止杂交及遗传渗入对物种遗传多样性的影响。     

Can transgenic rice cause ecological risks through transgene escape?

Alien transgene escape from genetically engineered rice to non-transgenic varieties or close wild relatives (including weedy rice) may lead to unpredictable ecological risks. However, for transgene escape to occur three conditions need to be met: (i) spatially, transgenic rice and its non-transgenic counterparts or wild relatives should have sympatric distributions; (ii) temporally, the flowering time of transgenic rice and the non-transgenic varieties or wild relatives should overlap; and (iii) biologically, transgenic rice and its wild relative species should have such a sufficiently close relationship that their interspecific hybrids can have normal generative reproduction. This paper presents research data on the geographic distribution, flowering habits, interspecific hybridization, and gene flow of cultivated rice (Oryza sativa) and its closely related wild relatives containing the AA genome. The objective is to estimate the possibility of transgene escape to non-transgenic rice varieties and wild relatives of rice, which may result in unpredictable ecological risks.     

基于基因组学的栎树生物学研究进展

栎树(Quercus spp.)是北半球重要的经济与生态树种。夏栎(Q. robur)、加州白栎(Q. lobata)、麻栎(Q. acutissima)等树种基因组的公布,对栎树生物学研究产生了深刻的影响。近5年来,栎树生物学出现了包括系统进化与物种鉴定、基因渐渗与适应进化、景观基因组学与生态保育、生物共存与互作机制、次生代谢与生长发育、DNA甲基化与表观遗传调控及基因与长寿机制等方面的研究热点。虽然基于基因组学的栎树生物学若干研究前沿已经形成,但尚处于起步阶段,笔者预期未来会向4个方面深入:①强调栎树基因组资源的深度应用。应用景观基因组学途径,探究栎树的杂交渐渗与适应进化;联合基因组、转录组、蛋白组等多组学技术,探究栎树生长发育与胁迫响应过程中的基因调控网络与信号通路;优化体细胞发生和遗传转化体系,攻克栎树遗传改良和基因资源开发技术瓶颈。②促进栎树研究体系的广度拓展。随着壳斗科其他树种全基因组序列的公布,基于从分子到群落的不同生物层次的模式系统,将对欧亚大陆和北美不同区域的栎树,包括白栎组、红栎组、冬青栎组、麻栎组等不同栎树类群,以及壳斗科其他属树种基因组生物学研究产生深远影响。③关注栎树资源利用的遗传与发育主题。用栎树基因组资源对其结构的、代谢的和农艺性状的差异及其优化加以解析,全基因组关联研究(GWAS)也将应用于栎树,从而为阐释木材发育和木栓形成的机制奠定基础。④聚焦栎林保育的生态与进化主题。在全球气候变化背景下,通过增加耐受胁迫的基因型,以缓解气候变化对森林生态系统的影响。同时维持和保护栎树在自然生态系统中的生态与进化过程,阐明栎树多样性、迁移与适应、趋异与趋同生态适应等方面进化成功的机制。