Genetic structuring and recent demographic history of red pandas (Ailurus fulgens) inferred from microsatellite and mitochondrial DNA

Clarification of the genetic structure and population history of a species can shed light on the impacts of landscapes, historical climate change and contemporary human activities and thus enables evidence‐based conservation decisions for endangered organisms. The red panda (Ailurus fulgens) is an endangered species distributing at the edge of the Qinghai‐Tibetan Plateau and is currently subject to habitat loss, fragmentation and population decline, thus representing a good model to test the influences of the above‐mentioned factors on a plateau edge species. We combined nine microsatellite loci and 551 bp of mitochondrial control region (mtDNA CR) to explore the genetic structure and demographic history of this species. A total of 123 individuals were sampled from 23 locations across five populations. High levels of genetic variation were identified for both mtDNA and microsatellites. Phylogeographic analyses indicated little geographic structure, suggesting historically wide gene flow. However, microsatellite‐based Bayesian clustering clearly identified three groups (Qionglai‐Liangshan, Xiaoxiangling and Gaoligong‐Tibet). A significant isolation‐by‐distance pattern was detected only after removing Xiaoxiangling. For mtDNA data, there was no statistical support for a historical population expansion or contraction for the whole sample or any population except Xiaoxiangling where a signal of contraction was detected. However, Bayesian simulations of population history using microsatellite data did pinpoint population declines for Qionglai, Xiaoxiangling and Gaoligong, demonstrating significant influences of human activity on demography. The unique history of the Xiaoxiangling population plays a critical role in shaping the genetic structure of this species, and large‐scale habitat loss and fragmentation is hampering gene flow among populations. The implications of our findings for the biogeography of the Qinghai‐Tibetan Plateau, subspecies classification and conservation of red pandas are discussed.     

Alpine headwater streams as reservoirs of remnant populations of the Danubian clade of brown trout

1. The watercourses of Austria are mainly part of the Danube drainage system. Nonetheless, only few brown trout (Salmo trutta) populations of the Danubian phylogenetic lineage have been found in this region, not being introgressed by hatchery‐reared fish of the allochthonous Atlantic lineage. The present study was aimed at identifying further waterbodies that might harbour the non‐admixed gene pool of the Danubian clade trout. 2. In a first step, the complete mitochondrial DNA control region of 447 specimens from 20 sampling sites was sequenced to screen for the presence of specific haplotypes. In a second step, 332 individuals from 15 populations were analysed at 10 microsatellite DNA loci. 3. Although sampling concentrated on remote Alpine headwater streams, introgression of hatchery strains was more common than expected from existing stocking records. For seven populations, however, no evidence of recent hatchery trout introgression was found and it is suggested that they might represent the indigenous gene pool. 4. Populations showing no evidence of hatchery introgression displayed lower levels of intrapopulation variability and higher degrees of differentiation compared to purported admixed populations. 5. Our study demonstrates the necessity of combining different molecular markers to reveal the impact of introgression into wild populations, since at some sampling sites admixture would have remained undetected if only a single molecular technique was applied. 6. The identification and characterisation of non‐introgressed populations provides important information for setting conservation priorities and preventing further loss of genetic integrity of a unique element of the native fish fauna.     

林跳鼠亚科的系统学研究述评

林跳鼠亚科分布在亚洲和北美洲,虽然种类及数量都不多,但对该亚科的分类和系统发育关系一直存在争议,近几年对林跳鼠哑科分子系统学的研究,产生了一些与形态学、生物地理学等研究不同的结果.本文对林跳鼠亚科系统学研究的一些工作加以述评,归纳出林跳鼠亚科在系统学方面还存在的问题,并对林跳鼠亚科系统学的进一步研究提出了一些建议.     

Phylogeny of the neotropical moth tribe Josiini (Notodontidae: Dioptinae): comparing and combining evidence from DNA sequences and morphology

DNA sequences were gathered from mitochondrial COII and nuclear ribosomal 18S and 28S genes for 21 moth species in the tribe Josiini (Notodontidae: Dioptinae) and two outgroup genera. These data complement a previously published morphological character set for the same taxa. We examine whether relationships in the Josiini are best reflected by a single phylogenetic analysis of all the data, or by a consensus of separate trees generated from DNA and morphology. Even in cases where analyses of partitioned data produce incongruent cladograms, the underlying disagreement between partitions is relatively small. While both molecular and morphological data provide useful character information by themselves, we conclude that the best supported phylogenetic hypothesis is the one derived from combined analysis.     

Polymorphic population genetic markers for the Australian wood cockroach Panesthia australis

Primers for five polymorphic nuclear DNA (nDNA) markers and one mitochondrial DNA (mtDNA) gene (COI) were developed for the Australian wood cockroach Panesthia australis using a range of techniques. Eight mitochondrial haplotypes and four to 36 alleles per nuclear locus were detected in 744 cockroaches. Observed heterozygosity ranged from 0.117 to 0.816 in a sample of 30 animals from one population. The markers will be useful for population biology and for the measurement of the effects of habitat fragmentation on this ecologically important forest‐dependent species.     

Variation in repeat length and heteroplasmy of the mitochondrial DNA control region along a core-edge gradient in the eastern spadefoot toad (Pelobates syriacus)

Peripheral populations are those situated at the distribution margins of a species and are often subjected to more extreme abiotic and biotic conditions than those at the core. Here, we hypothesized that shorter repeat length and fewer heteroplasmic mitochondrial DNA (mtDNA) copies, which are associated with more efficient mitochondrial function, may be related to improved survival under extreme environmental conditions. We sampled eastern spadefoot toads (mostly as tadpoles) from 43 rain pools distributed along a 300-km gradient from core to edge of the species' distribution. We show that mean pool tandem repeat length and heteroplasmy increase from edge to core, even after controlling for body size. We evaluate several alternative hypotheses and propose the Fisher hypothesis as the most likely explanation. However, additional sequential sampling and experimental studies are required to determine whether selection under extreme conditions, or alternative mechanisms, could account for the gradient in heteroplasmy and repeat length in the mtDNA control region.     

克隆绵羊——多莉(DOLLY)的研究进展

多莉,第一例大型克隆哺乳动物,由一只称为FinnDorset的6岁母羊乳腺体细胞的基础生命物质经细胞核转移等操作而产生。成果公布后,持怀疑观点的学者提出,提供体细胞的母羊是否本身处在妊娠状态?推测多莉是由胚胎细胞产生,并非体细胞本身克隆所致。由于6岁的母羊死于1995年,只能用其冷冻保存的乳腺组织在Hannah研究中心进行细胞群体的分析。首先,用微卫星扩增技术,以三套引物进行测定;其次,进行DNA指纹分析来断定供体体细胞起源,以确定多莉的真实性。最后证实多莉来自成年母羊乳腺的体细胞。     

Searching for DNA in museum specimens: a comparison of sources in a mammal species

The number of genetic studies that use preserved specimens as sources of DNA has been steadily increasing during the last few years. Therefore, selecting the sources that are more likely to provide a suitable amount of DNA of enough quality to be amplified and at the minimum cost to the original specimen is an important step for future research. We have compared different types of tissue (hides vs. bones) from museum specimens of Iberian lynx and multiple alternative sources within each type (skin, footpad, footpad powder, claw, diaphysis, maxilloturbinal bone, mastoid process and canine) for DNA yield and probability of amplification of both mitochondrial and nuclear targets. Our results show that bone samples yield more and better DNA than hides, particularly from sources from skull, such as mastoid process and canines. However, claws offer an amplification success as high as bone sources, which makes them the preferred DNA source when no skeletal pieces have been preserved. Most importantly, these recommended sources can be sampled incurring minimal damage to the specimens while amplifying at a high success rate for both mitochondrial and microsatellite markers.