中国中西部五大山系间社鼠头骨形态的地理分化

种群分化是物种形成过程中的关键一步,通过形态特征进行种内变异的探讨对揭示微进化过程具有积极
意义。本文以社鼠头骨为材料,通过SPSS 统计分析软件对采集自我国中西部5 大山系的250 号标本头骨形态变
量进行了判别函数分析,结果表明秦岭与四川各山系之间社鼠头骨已发生完全分化,而在四川各山系之间,除
邛崃和相岭山系外,其余各山系社鼠头骨形态已分化明显。腭长、上颌齿隙长等变量是各山系社鼠头骨样本发
生分化的主要变量,暗示上述山系之间社鼠头骨形态的分化可能主要来自于局部种群在食物资源及觅食习性等
方面的差异。除此之外,本文研究结果尚揭示了在对具有广泛分布的小型兽类进行种下阶元(如亚种) 的划分
时,需充分考虑形态特征可能存在的地理差异。     

不同森林类型中社鼠食性和消化道形态变化

能量的获取能力、分配速率和效率对动物的生存繁衍起着至关重要的作用(王德华和王祖望,2000;刘艳华等,2004),消化道作为储藏和处理食物及吸收能量的场所,其形态学和生理学决定着动物对营养物质和能量的吸收(汪晓琳等,2007;朱万龙等,2009).在面对外界环境变化带来的各种压力和胁迫下,小型哺乳动物的消化道各器官常常会产生不同程度的响应(Derting and Noakes,1995;张志强和王德华,2009).     

蜂桶寨自然保护区中华姬鼠和社鼠肥满度的研究

我们于2008年4~11月对四川蜂桶寨自然保护区内中华姬鼠(Apodemus draco)和社鼠(Niviventer confucianus)肥满度在各年龄组及不同季节中的变化进行了研究,并初步分析了影响因素。结果显示：中华姬鼠肥满度在各年龄组中的性别差异不明显;在各年龄组间的差异显著,其变化趋势为老年组＞成年组＞亚成年组＞幼年组,亚成年组及老年组肥满度在各季节间无显著差异,而成年组则差异明显。社鼠肥满度在各年龄组间无显著性差异,亚成年组肥满度在各季节间差异显著,同时成年组及老年组肥满度在季节间无显著差异;二物种,亚成年组、成年组及老年组肥满度与海拔无明显的线性关系。分析认为,繁殖期能量的消耗的增加可能导致中华姬鼠肥满度在繁殖期下降,而社鼠成年及老年个体面对食物资源、能量需求等方面的季节变化,能够通过相应的调节,维持肥满度的稳定。     

不同生境和季节社鼠与大林姬鼠的微生境选择比较

微生境选择分化是生境相似的物种间共存的重要原因。社鼠和大林姬鼠为北京东灵山地区常见鼠种,生境需求、活动节律及食物组成等相似,但二者共存的原因尚不清楚。2016—2017年,我们对北京东灵山地区社鼠和大林姬鼠的微生境选择进行了研究。不同季节和生境类型中,社鼠和大林姬鼠微生境选择存在明显分化。灌丛生境中,春季社鼠偏好于乔木密度、草本盖度更高和落叶盖度相对偏低的微生境,而大林姬鼠选择郁闭度、落叶盖度较高而草本盖度较低的微生境;主成分分析表明,地表覆盖物是影响二者微生境选择的主要因素;秋季社鼠喜好乔木种类多、灌木密度和草本盖度更高的微生境,而大林姬鼠选择乔木胸径、灌木距离、落叶盖度和空地比例更高的微生境,食物丰富度是影响社鼠和大林姬鼠微生境选择的主要因素。弃耕地生境中,春季社鼠倾向于灌木密度和草本盖度较高的微生境,而大林姬鼠首选郁闭度、乔木胸径、落叶盖度较大而草本盖度较低的微生境,地表覆盖物是影响二者微生境选择的主要因素;秋季社鼠偏好郁闭度和落叶盖度都相对较低的微生境,大林姬鼠则相反,食物多度是影响二者微生境选择的主要因素。次生林生境中,春季因样本量太少,未作分析;秋季社鼠优先选择灌木密度、灌木基径和草本盖度更高的微生境,大林姬鼠更倾向乔木胸径、落叶盖度较高,而灌木密度、草本盖度较低的微生境,地表覆盖物是影响二者微生境选择的主要因素。结果表明,不同生境和季节,两种鼠的微生境选择具有明显分化,这可能是二者共存的重要原因之一。     

光周期对社鼠能量摄入的影响

Digested energy, metabolizable energy, digestibility and assimilation rate were quantified at different photoperi-ods in Niviventer confucianus using the food balance method. Three photoperiods were applied: a short photoperiod (8L:16D), normal photoperiod (12L: 12D) and a long photoperiod (16L: 8D). The results show that digestibility and as-similation rate were highest in the short photoperiod with values of 83.97% 1.16% and 80.46% 1.34%, and lowest in the normal photoperiod with values of 81.74% _ 1.76% and 78.45% 1.41%. Moreover, the energy intake, di-gestibility and assimilated energy of N. confucianus decreased with the amount of daylight. The statistical significance of the results obtained by a one-factor analysis of variance were all less than 0.01 or 0.05 except for digested energy. This indicates that photoperiod is an important environmental factor to affect the energy metabolism of Niviventer confucianus。     

蜂桶寨自然保护区中华姬鼠和社鼠食性的季节变化及与肠道长度的关系

为揭示啮齿动物食性及其对消化道肠道长度的影响,我们于2008 年在四川省宝兴县蜂桶寨国家级自然保护区内以中华姬鼠和社鼠为对象展开了研究。结果发现社鼠和中华姬鼠均以摄食种子为主,食谱中各食物成分在性别之间无显著差异,但季节变化明显。在各食物成分中,摄入种子百分比与中华姬鼠及社鼠小肠长之间呈显著正相关,而昆虫成分则相反。分析认为,中华姬鼠和社鼠取食食物成分的季节变化,可能与不同季节中食物资源可获得性的不同有关,消化道长度的变化可能体现了对季节性食物资源和能量需求的适应.     

Autosomal polymorphism due to pericentric inversions in the deer mouse (peromyscus maniculatus), and some evidence of somatic segregation

The existence of extensive autosomal polymorphism due to pericentric inversions in a colony of deer mice, Peromyscus maniculatus, has been reported (Arakaki and Sparkes, personal communication). A background of intersubspecific hybridization was suspected to have contributed to the observed polymorphism. The present study describes findings on two separate subspecies, P. m. hollisteri and P. m. bairdii. Autosomal polymorphism existed within each subspecies. In P. m. bairdii, the two polymorphic autosomal pairs were identified. In one pair, a large subterminal element was homologous to an acrocentric of comparable size, while in the other pair, a small mediocentric and an acrocentric were homologous. Among splenic cells of animals made heteromorphic for the larger of the two autosomal pairs, the tendency toward reconstitution of homomorphic cell types was observed. This was taken as evidence of somatic segregation among immunologically competent cells.Dedicated to Professor J. Seiler on the occasion of his 80th birthday.This work was supported in part by grant CA-05138 from the National Cancer Institute, U. S. Public Health Service. Contribution Number 53-65, Department of Biology, City of Hope Medical Center.     

Sequential meiotic prophase development in the pubertal Indian pygmy field mouse: synaptic progression of the XY chromosomes, autosomal heterochromatin, and pericentric inversions.

Sequential meiotic prophase development has been followed in the pubertal male pygmy mouse Mus terricolor, with the objective to identify early meiotic prophase stages. The pygmy mouse differs from the common mouse by having large heterochromatic blocks in the X and Y chromosomes. These mice also show various chromosomal mutations; for example, fixed variations of autosomal short arms heterochromatin among different chromosomal species and pericentric inversion polymorphism. Identification of prophase stages was crucial to analyzing effects of heterozygosity for these chromosomal changes on the process of homologous synapsis. Here we describe identification of the prophase stages in M. terricolor, especially the pachytene substages, on the basis of morphology of the XY bivalent. Based on this substaging, we show delayed pairing of the heterochromatic short arms, which may be the reason for their lack of chiasmata. The identification of precise pachytene substages also reveals an early occurrence of "synaptic adjustment" in the pericentric inversion heterobivalents, a mechanism that would prevent chiasma formation in the inverted segment and thereby would abate adverse effects of such heterozygosity. The identification of pachytene substages would serve as the basis to analyze the nature of synaptic anomalies met in M. terricolor hybrids (which will be the basis of a subsequent paper).     

BRCA1 foci in normal S-phase nuclei are linked to interphase centromeres and replication of pericentric heterochromatin

Breast cancer-associated protein 1 (BRCA1) forms foci at sites of induced DNA damage, but any significance of these normal S-phase foci is unknown. BRCA1 distribution does not simply mirror or overlap that of replicating DNA; however, BRCA1 foci frequently abut sites of BrdU incorporation, mostly at mid-to-late S phase. Although BRCA1 does not overlap XIST RNA across the inactive X chromosome, BRCA1 foci position overwhelmingly in heterochromatic regions, particularly the nucleolar periphery where many centromeres reside. In humans and mice, including early embryonic cells, BRCA1 commonly associates with interphase centromere-kinetochore complexes, including pericentric heterochromatin. Proliferating cell nuclear antigen or BrdU labeling demonstrates that BRCA1 localizes adjacent to, or "paints," major satellite blocks as chromocenters replicate, where topoisomerase is also enriched. BRCA1 loss is often associated with proliferative defects, including postmitotic bridges enriched with satellite DNA. These findings implicate BRCA1 in replication-linked maintenance of centric/pericentric heterochromatin and suggest a novel means whereby BRCA1 loss may contribute to genomic instability and cancer.     

Polymorphism and polytypy for pericentric inversions in 38-chromosome Mastomys (Rodentia, Murinae) and possible taxonomic implications.

Chromosome banding analysis (R- and C-bands) of two 38-chromosome Mastomys specimens originating from the Ivory Coast and Uganda revealed different numbers of autosome arms (NFa), equal to 51 and 60, respectively. Comparison of their chromosome banding patterns with those of Mastomys specimens from the Sudan (NFa = 41) and Senegal (NFa = 51-54), studied previously, showed that variation of the NFa from 40 to 60 throughout the species distribution is the result of a pericentric inversion polymorphism involving 3-12 chromosome pairs. At the population level, this variation is much narrower and never results from more than two chromosome pairs involved in inversion polymorphism. Taking into account that the NFa values recorded to date form a well-defined discontinuous row, we presume that introgressive hybridization between populations differing from each other by 3-5 to 11-12 pericentric inversions is interrupted. From there, the hypothesis of the existence of at least three cryptic species (designated provisionally as MER-1, MER-2, and MER-3) within 38-chromosome Mastomys populations previously assigned to M. erythroleucus can be made. It looks likely that one of them, possessing a karyotype with an NFa = 50-56, is widely distributed throughout sub-Saharan Africa and includes karyotyped populations from Senegal, the Ivory Coast, Mali, Benin, Cameroon, Zaire, and the Sudan. The second species (MER-2) includes the specimens karyotyped (NFa = 40-41) from Chad and the Sudan. Finally, a third tentative species (MER-3) corresponds to specimens with NFa = 59-60 found in East Zaire and Uganda, as well as possibly Mali and Chad.     

Chromosomal inversions and ecotypic differentiation in Anopheles gambiae: the perspective from whole‐genome sequencing

The molecular mechanisms and genetic architecture that facilitate adaptive radiation of lineages remain elusive. Polymorphic chromosomal inversions, due to their recombination‐reducing effect, are proposed instruments of ecotypic differentiation. Here, we study an ecologically diversifying lineage of Anopheles gambiae, known as the Bamako chromosomal form based on its unique complement of three chromosomal inversions, to explore the impact of these inversions on ecotypic differentiation. We used pooled and individual genome sequencing of Bamako, typical (non‐Bamako) An. gambiae and the sister species Anopheles coluzzii to investigate evolutionary relationships and genomewide patterns of nucleotide diversity and differentiation among lineages. Despite extensive shared polymorphism and limited differentiation from the other taxa, Bamako clusters apart from the other taxa, and forms a maximally supported clade in neighbour‐joining trees based on whole‐genome data (including inversions) or solely on collinear regions. Nevertheless, F_ST outlier analysis reveals that the majority of differentiated regions between Bamako and typical An. gambiae are located inside chromosomal inversions, consistent with their role in the ecological isolation of Bamako. Exceptionally differentiated genomic regions were enriched for genes implicated in nervous system development and signalling. Candidate genes associated with a selective sweep unique to Bamako contain substitutions not observed in sympatric samples of the other taxa, and several insecticide resistance gene alleles shared between Bamako and other taxa segregate at sharply different frequencies in these samples. Bamako represents a useful window into the initial stages of ecological and genomic differentiation from sympatric populations in this important group of malaria vectors.     

Chromosomal polymorphisms in African vlei rats, Otomys irroratus (Muridae: Otomyini), detected by banding techniques and chromosome painting: inversions, centromeric shifts and diploid number variation

Pericentric inversions are important for evolutionary biology because of their potential role in speciation. They may result in reproductive isolation due to illegitimate pairing of homologues at meiosis which leads to the production of aneuploid gametes (containing deletions or duplications of chromosomal segments), and consequently mediate chromosomal divergence. In this study, we describe the prevalence of pericentric inversions in the African vlei rat, Otomys irroratus (OIR). The species is characterized by intraspecific chromosomal variation (2n = 23-32) across its distribution in southern Africa. Here, we analyzed 55 individuals collected from 7 localities in South Africa by G- and C-banding and chromosome painting with flow sorts of Myotomys unisulcatus. Of the 55 specimens that were analyzed, 47% contained inversions or centromeric shifts on 4 autosomes (OIR1, 4, 6 and 10) which were present singly in specimens (i.e. none of the specimens contained all 4 inversions concurrently). These inversions were found in both homozygous and heterozygous state over a wide geographic range suggesting that they are floating polymorphisms. Given the potential role of inversions in post-mating isolation (through production of aneuploid gametes), the prevalence of inversions as floating polymorphisms in the vlei rats suggests that they are probably retained in the population through suppression of recombination in the inverted regions of the chromosomes.     

Karyotypes of three rat species (Mammalia: Rodentia: Muridae) from Hainan Island, China, and the valid specific status of Niviventer lotipes

The karyotypes of three rat species from Hainan Island, China, were examined. Niviventer fulvescens (Gray, 1847) had 2n=46 and FN=64, similar to the karyotypes reported for N. fulvescens from Southeast Asia, while Niviventer lotipes () had 2n=52 and FN=66, which is distinct from the known karyotypes of other Niviventer species. Niviventer lotipes was recently considered conspecific with N. tenaster (), but the two were found to have extremely different karyotypes (2n=52 and FN=66 in N. lotipes; 2n=46 and FN=54 in N. tenaster). Therefore, in this paper N. lotipes is considered a valid species for the first time; it is distinct from N. tenaster and endemic to Hainan Island, where N. lotipes is differentiated from N. fulvescens by larger body and skull sizes, a shorter tail, and darker coloration. Rattus nitidus (Hodgson, 1845) from Hainan Island had 2n=42 and FN=62, which is similar to the reported karyotypes of conspecific populations in Southeast Asia.     

Characterization and comparative analysis of DNA from the pericentric heterochromatin of chromosome 2 of Anopheles atroparvus V. Tiel (Culicidae, Diptera)

The minilibrary containing DNA sequences from the diffuse pericentric heterochromatin from the right arm of Anopheles atroparvus V. Tiel (Culicidae, Diptera) chromosome 2 (2R) was generated by use of chromosome microdissection technique. Southern-blot hybridization of the minilibrary fragments with the labeled genomic DNA of A. atroparvus and analysis of their primary structure showed that this heterochromatin region contained repeated DNA sequences differed by their primary structure and the number of copies. These were mostly AT-rich sequences harboring the features characteristic of the S/MAR regions. Based on the clones homology to the sequences from the An. gambiae and Drosophila melanogaster genomes, it was demonstrated that the pericentric heterochromatin from the right arm of An. atroparvus chromosome 2 contained gypsy-like transposable elements, as well as the sequences homologous to the structural genes. In situ hybridization with the chromosomes of A. atroparvus and of the two representatives of the Anopheles maculipennis species complex, A. messeae and A. beklemishevi, showed that pericentric regions of all these chromosomes contained DNA sequences homologous to the sequences from the region-specific minilibrary. Cloned fragments of conserved repetitive DNA revealed upon interspecific Southern-blot hybridization of the clones with the labeled genomic DNA of A. messeae can be utilized in further investigations of evolutionary rearrangements of the pericentric heterochromatin within the Anopheles maculipennis species complex.     

Chromosomal diversification of diploid number,heterochromatin and rDNAs in two species of Phanaeus beetles (Scarabaeidae,Scarabaeinae)

The genus Phanaeus is included in the tribe Phanaeini, one of the most diverse tribes within the subfamily Scarabaeinae in terms of chromosomal characteristics. However, so far the species of this genus were not studied with differential cytogenetic techniques, limiting any inference of the probable mechanisms responsible for this diversity. In this work, several techniques were applied with the aim of cytogenetically characterizing two Phanaeus species. The karyotype found for Phanaeus (Notiophanaeus) chalcomelas was 2n = 12, neo-XY, and that of P. (N.) splendidulus was 2n = 20, Xy_p, considered primitive for the family Scarabaeidae. The chromosomes of both species showed a high amount of constitutive heterochromatin (CH), with blocks rich in base pairs GC (CMA₃⁺). Moreover, in P. (N.) chalcomelas the marks revealed by C-banding and fluorochrome staining were different in size, showing CH variability. Sites of 18S ribosomal DNA (rDNA) were identified in one autosomal pair of P. (N.) chalcomelas and in five autosomal pairs of P. (N.) splendidulus. On the other hand, only one autosomal pair exhibited 5S rDNA sequences in these species. The results suggest that the karyotype differentiation of the Phanaeus species studied here involved pericentric inversions and centric fusions, as well as mechanisms related to amplification and dispersion of CH and rDNA sequences.     

Chromosomal aberrations in environmentally exposed population in relation to metabolic and DNA repair genes polymorphisms

The capital city of Prague is one of the most polluted localities of the Czech Republic. Therefore, the effect of exposure to carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) adsorbed onto respirable air particles (<2.5 μm) on chromosomal aberrations was studied in a group of policemen (males, aged 22–50 years) working in the downtown area of Prague and spending daily >8 h outdoors (N = 53). Age- and sex-matched healthy volunteers spending > 90% daily time indoors were chosen as controls (N = 52). Ambient air particles (PM10, PM2.5) and c-PAHs were monitored using versatile air pollution sampler (VAPS), and personal exposure was evaluated using personal samplers during working shift. Chromosomal aberrations were analyzed by conventional cytogenetic analysis and fluorescent in situ hybridization (FISH). Urinary cotinine plasma levels of vitamins A, E and C, folate, total cholesterol, HDL, LDL cholesterols and triglycerides were also analyzed as possible effect modifiers. Genotypes CYP1A1*2A, CYP1A1*2C, GSTM1, GSTP1, GSTT1, EPHX1, NAT2, hOGG1, XRCC1, XPD, p53 BstI, p53 MspI, MTHFR677, and MS2656 were determined by PCR-based RFLP assays. The following levels of air pollution were recorded during the study period (mean from HiVol sampling): PM10 62.6 μg/m³, c-PAHs 24.7 ng/m³, B[a]P 3.50 ng/m³. The conventional cytogenetic analysis did not reveal any differences between the group of policemen exposed to the ambient air pollution and the control group. The cytogenetic analysis by FISH analysis used the whole chromosome painting probes for chromosomes #1 and #4 (Cambio, UK). It detected a significant increase in all studied endpoints in the policemen compared to controls (% AB.C. = 0.33 ± 0.25 versus 0.24 ± 0.18, p < 0.05, F_G/100 = 1.72 ± 1.57 versus 1.25 ± 1.11, p < 0.05, AB/1000 (aberrations/1000 cells) = 5.58 ± 4.62 versus 3.90 ± 3.06, p < 0.05). CYP1A1*2C (Ile/Ile), XPD 23 (Lys/Lys), and XPD 6 (CC) genotypes were associated with an increase of aberrant cells by conventional method. Factors associated with an increased level of translocations by FISH included age, smoking, B[a]P-like DNA adducts (corresponding to the exposure of c-PAHs), folate, polymorphisms of CYP1A1*2C, GSTP1, EPHX1, p53 MspI and MTHFR. Ambient air exposure to c-PAHs significantly increased FISH cytogenetic parameters in nonsmoking policemen. We may conclude that FISH indicates that the city policemen in Prague represent a group of increased genotoxic risk. This is the first study that has reported a relationship between DNA adducts (biomarker of exposure) and chromosomal aberrations by FISH (biomarker of effect).