内蒙古锡林河流域不同生境中蝗虫种类组成的分析

本文对内蒙古锡林河流域不同生境中蝗虫种类发生的情况进行了分析。经过系统取样和大面积扫网调查,共采集到蝗虫21种,这些种类在各生境中出现的情况,与生境的复杂程度存在很大的关系。在复杂的生境中,蝗虫种类最丰富。根据锡林河流域不同生境中蝗虫种类发生的情况,经过比较分析,我们认为在该区域存在的沙带生境是典型草原的“蝗虫库”。“蝗虫库”的存在,对牧业生产构成一定的潜在威胁。经存在度分析表明,一些常见的种类,生态分布幅度宽,同时,它们又是当地的优势种害虫,为害大,是重点防治对象。     

Reconsidering the Role of Absentee Herd Owners: A View from Mongolia

Since the privatization of livestock in 1992, rates of absentee ownership of livestock have increased sharply in Mongolia. Unlike other documented instances of absentee herding in pastoral societies, absentee herd ownership has few detrimental ecological or social impacts in Mongolia. Rather, the relationship between absentee herd owners and herders may be viewed as a revitalized institution, with links to customary patterns of urban-rural exchange, emerging to meet the needs of both herders and town-dwellers during the transition from a socialist planned economy to a free market economy. Absentee herding in Mongolia differs from absentee and contract herding accounts from Africa and the Middle East in its continuing emphasis on subsistence rather than speculative investment and accumulation. Other important distinctions include: (1) absentee owners and herders are usually kin or friends; (2) herders tend their own private herds in addition to absenteeowned animals;(3)few ethnic, caste, or class differences existbetween herders and absentee herd owners; and (4) herders from all wealth strata tend absentee-owned animals. Policies to restrict or regulate absentee livestock ownership must be carefully considered in the Mongolian context, making clear distinctions between informal, mutually beneficial subsistence-driven arrangements among kin and friends, and more formal investment-driven contracts between businesses or investors and herders.     

内蒙古高原四种针茅种群年龄与株丛结构的研究

用样带法调查了内蒙古高原4种针茅(StipaL.)的年龄结构,并将其年龄划分为5个阶段:幼苗、幼龄、成年、老龄前期和老龄期。结果表明:幼苗对种群年龄结构和动态有较大的影响,针茅幼苗的存活率通常很低,而成年株丛的存活率较高,株丛的实际寿命很长,老龄株丛在种群中占有较大的比例。4种针茅中大针茅(S.grandisP.Smirn.)和克氏针茅(S.kryloviiRoshev.)的幼苗比例较高,从贝加尔针茅(S.baicalensisRoshev.)群落到小针茅(S.klemenziiRoshev.)群落种群中幼龄和成年株丛比例呈下降的趋势,而老龄株丛比例呈增加的趋势;针茅属植物在株丛水平上的动态主要表现为株丛的破碎与枝条自疏过程,以及株丛生殖枝数量和营养枝生物量的波动,幂函数模型Y=aXb可以对株丛的枝条自疏过程进行定量描述     

内蒙古科尔沁草原黑玉蚂蚁巢窝中华二索线虫及黑玉蚂蚁索幼虫的观察

内蒙科尔沁草原是牛羊胰脏阔盘吸虫病及肝脏双腔吸虫病严重的流行区。作者从双腔吸虫的昆虫宿主（第二中间宿主） 黑玉蚂蚁（Ｆｏｒｍｉｃａ ｇａｇａｔｅｓ） 腹中查获索线虫幼虫, 检到从黑玉蚂蚁腹部自动弹出的后感染期的索幼虫。与此后感染期索幼虫同形态的索幼虫在黑玉蚂蚁巢窝土壤中也找到。黑玉蚂蚁巢窝土壤中有数种索科线虫, 仅中华二索线虫（ Ａｍｐｈｉｍｅｒｍｉｓｃｈｉｎｅｎｓｉｓ） 的雌雄成虫在长细大小以及形态结构上与黑玉蚂蚁索幼虫相像, 它们是否同一种类尚待实验证实。     

Inner structural organization of the distal humerus in Paranthropus and Homo

The taxonomic attribution of isolated hominin distal humeri has been a matter of uncertainty and disagreement notwithstanding their relative abundance in the fossil record. Four taxonomically-based morphotypes, respectively representing P. boisei, P. robustus, non-erectus early Homo and H. erectus, have been identified based on the cross-sectional outer shape variation of an assemblage of Plio-Pleistocene eastern and southern African specimens (Lague, 2015). However, the existence of possible differences between Paranthropus and Homo in the inner structural organisation at this skeletal site remains unexplored. We used noninvasive imaging techniques to tentatively characterize the endostructural organization of five early Pleistocene distal humeri from South Africa (TM 1517g, SK 24600, SKX 10924, SKX 34805) and Ethiopia (Gombore IB), which have been variably attributed to Paranthropus or Homo. While the investigated specimens reveal diverse degrees of inner preservation related to their taphonomic and diagenetic history, in all but SK 24600 from Swartkrans we could comparatively assess some geometric properties at the most distal cross-sectional level (%CA, I_x/I_y, I_max/I_min) and quantify cortical bone thickness topographic variation across the preserved shaft portions by means of a 2-3D Relative Cortical Thickness index. Whenever possible, we also provided details about the site-specific organization of the cancellous network and measured the same parameters in a comparative sample of twelve adult extant humans. For most features, our results indicate two main patterns: the first includes the specimens TM 1517g, SKX 10924 and SKX 34805, while the second endostructural morphotype sets apart the robust Homo aff. erectus Gombore IB specimen from Melka Kunture, which more closely resembles the condition displayed by our comparative human sample. Notably, marked differences in the amount and pattern of proximodistal cortical bone distribution have been detected between Gombore IB and SKX 34805 from Swartkrans. Given its discordant outer and inner signatures, we conclude that the taxonomic status of SKX 34805 deserves further investigations.     

Germination ecology of Central Asian Stipa spp: differences among species, seed provenances, and the importance of field studies

Stipa-species are wide-spread in Central Asia, but sexual reproduction in the dry steppes is rare. To facilitate conservation and restoration of these important rangelands, we studied germination characteristics of three common Mongolian Stipa-species under field- and lab conditions. Seeds of Stipa krylovii, Stipa gobica and Stipa glareosa were sown at the study site in Southern Mongolia over two consecutive years during which period tests were carried out to ascertain whether competition or herbivory are the main constraints of seedling establishment. In addition, we tested germination and seed viability in the laboratory under two different temperature regimes (20/10°C and 8/4°C), as well as the effect of cold-stratification. The lab experiments also included S. krylovii seeds originating from three climatically different provenances. None of the three Stipa-species seedlings emerged during the first 2 years of the field study. However, after an unusually intense rain event in the third year, 3% of S. krylovii, 0.6% of S. glareosa and 0.1% of S. gobica seeds germinated in the study plots. The factors ‘sowing-year’ and ‘vegetation’ significantly affected seedling emergence, whereas grazing had no effect at all. Under laboratory conditions a high percentage of viable seeds of S. gobica and S. glareosa germinated at both incubation temperatures, and cold-stratification had no effect on germination or viability. Germination of S. krylovii seeds required warmer temperatures and cold-stratification had a positive effect. Such evidence for dormancy was more pronounced in seeds from the moister, northern provenances. Germination of Stipa-species in the field is rare and only possible under exceptionally moist conditions. Conservation should thus concentrate on steppe conservation rather than on restoration. Where artificial reseeding is necessary, differences among species and also among different seed provenances should be taken into account.     

Diversity of bacteria that nodulate Prosopis juliflora in the eastern area of Morocco

A total of 274 bacterial strains were isolated from the root nodules of Prosopis juliflora, growing in two arid soils of the eastern area of Morocco. A physiological plate screening allowed the selection of 15 strains that could tolerate NaCl concentrations between 175 and 500 mM. These were compared with 15 strains chosen from among the ones which did not tolerate high salinity. The diversity of strains was first assessed by rep-PCR amplification fingerprinting using BOXA1R and ERIC primers. An analysis of the PCR-amplified 16S rDNA gene digestion profiles using five endonucleases indicated the presence of different lineages among the taxa associated with P. juliflora nodules in the soils studied. Nucleotide sequencing of the small subunit rRNA gene and BLAST analysis showed that P. juliflora could host at least six bacterial species in this region and that the identity of those associated with high salt tolerance was clearly distinct from that of the salt-sensitive ones. Among the former, the first type displayed 99% similarity with different members of the genus Sinorhizobium, the second 97% similarity with species within the genus Rhizobium, while the third ribosomal type had 100% homology to Achromobacter xylosoxidans. Within the salt-sensitive isolates the prevailing type observed showed 98% similarity with Rhizobium multihospitium and R. tropici, a second type had 98% similarity to R. giardinii, and a further case displayed 97% colinearity with the Ensifer group including E. maghrebium and E. xericitae. All of the thirty strains encompassing these types re-nodulated P. juliflora in microbiologically controlled conditions and all of them were shown to possess a copy of the nodC gene. This is the first report detecting the betaproteobacterial genus Achromobacter as nodule-forming species for legumes. The observed variability in symbiont species and the abundance of nodulation-proficient strains is in line with the observation that the plant always appears to be nodulated and efficiently fixing nitrogen in spite of a wide range of soil and environmental conditions.     

miR-17 family miRNAs are expressed during early mammalian development and regulate stem cell differentiation

MicroRNAs are small non-coding RNAs that regulate protein expression by binding 3′UTRs of target mRNAs, thereby inhibiting translation. Similar to siRNAs, miRNAs are cleaved by Dicer. Mouse and ES cell Dicer mutants demonstrate that microRNAs are necessary for embryonic development and cellular differentiation. However, technical obstacles and the relative infancy of this field have resulted in few data on the functional significance of individual microRNAs. We present evidence that miR-17 family members, miR-17-5p, miR-20a, miR-93, and miR-106a, are differentially expressed in developing mouse embryos and function to control differentiation of stem cells. Specifically, miR-93 localizes to differentiating primitive endoderm and trophectoderm of the blastocyst. We also observe high miR-93 and miR-17-5p expression within the mesoderm of gastrulating embryos. Using an ES cell model system, we demonstrate that modulation of these miRNAs delays or enhances differentiation into the germ layers. Additionally, we demonstrate that these miRNAs regulate STAT3 mRNA in vitro. We suggest that STAT3, a known ES cell regulator, is one target mRNA responsible for the effects of these miRNAs on cellular differentiation.     

Active cell movements coupled to positional induction are involved in lineage segregation in the mouse blastocyst

In the mouse blastocyst, some cells of the inner cell mass (ICM) develop into primitive endoderm (PE) at the surface, while deeper cells form the epiblast. It remained unclear whether the position of cells determines their fate, such that gene expression is adjusted to cell position, or if cells are pre-specified at random positions and then sort. We have tracked and characterised dynamics of all ICM cells from the early to late blastocyst stage. Time-lapse microscopy in H2B-EGFP embryos shows that a large proportion of ICM cells change position between the surface and deeper compartments. Most of this cell movement depends on actin and is associated with cell protrusions. We also find that while most cells are precursors for only one lineage, some give rise to both, indicating that lineage segregation is not complete in the early ICM. Finally, changing the expression levels of the PE marker Gata6 reveals that it is required in surface cells but not sufficient for the re-positioning of deeper cells. We provide evidence that Wnt9A, known to be expressed in the surface ICM, facilitates re-positioning of Gata6-expressing cells. Combining these experimental results with computer modelling suggests that PE formation involves both cell sorting movements and position-dependent induction.