Molecular phylogenetics and biogeography of Lepus in Eastern Asia based on mitochondrial DNA sequences

In spite of several classification attempts among taxa of the genus Lepus, phylogenetic relationships still remain poorly understood. Here, we present molecular genetic evidence that may resolve some of the current incongruities in the phylogeny of the leporids. The complete mitochondrial cytb, 12S genes, and parts of ND4 and control region fragments were sequenced to examine phylogenetic relationships among Chinese hare taxa and other leporids throughout the World using maximum parsimony, maximum likelihood, and Bayesian phylogenetic reconstruction approaches. Using reconstructed phylogenies, we observed that the Chinese hare is not a single monophyletic group as originally thought. Instead, the data infers that the genus Lepus is monophyletic with three unique species groups: North American, Eurasian, and African. Ancestral area analysis indicated that ancestral Lepus arose in North America and then dispersed into Eurasia via the Bering Land Bridge eventually extending to Africa. Brooks Parsimony analysis showed that dispersal events followed by subsequent speciation have occurred in other geographic areas as well and resulted in the rapid radiation and speciation of Lepus. A Bayesian relaxed molecular clock approach based on the continuous autocorrelation of evolutionary rates along branches estimated the divergence time between the three major groups within Lepus. The genus appears to have arisen approximately 10.76 MYA (+/- 0.86 MYA), with most speciation events occurring during the Pliocene epoch (5.65 +/- 1.15 MYA similar to 1.12 +/- 10.47 MYA). (c) 2005 Elsevier Inc. All rights reserved.

Threatened fishes of the world: Tanichthys albonubes Lin 1932 (Cyprinidae)

The white cloud mountain minnow Tanichthys albonubes Lin is an endemic species to southern China and the genus has two species, Tanichthys albonubes Lin and Tanichthys micagemmae Freyhof et Herder. The distribution range of T. albonubes Lin and T. micagemmae is very narrow and only found in the mountain brooks of Baiyunshan Mountain (White Cloud Mountain), Huaxian Country and the vicinity of Guangzhou in Guangdong Province and Halong, Quang Ninh Province, Vietnam respectively. The wild populations of this fish had already been on the verge of extinction when Shu-Yan Lin first discovered it in 1932 at the Baiyunshan Mountain. It was believed to be extinct in the wild because there were no reports of this fish in the wild since 1980. In September 2003, a small and isolated population of the fish was discovered in a mountain puddle in the north vicinity of Guangzhou. Additional studies are needed to determine the survival and propagation of the released fish. The protection of their natural habitat should be implemented.

Band-tail shape and transport near the metal-insulator transition in Si-doped

In the present work, an infrared light-emitting diode is used to photodope molecular-beam-epitaxy-grown Si: Al0.3Ga0.7As, a well-known persistent photoconductor, to vary the effective electron concentration of samples in situ. Using this technique, we examine the transport properties of two samples containing different nominal doping concentrations of Si [1 x 10(19) cm(-3) for sample 1 (S1) and 9 x 10(17) cm(-3) for sample 2 (S2)] and vary the effective electron density between 10(14) and 10(18) cm(-3). The metal-insulator transition for S1 is found to occur at a critical carrier concentration of 5.7 x 10(16) cm(-3) at 350 mK. The mobilities in both samples are found to be limited by ionized impurity scattering in the temperature range probed, and are adequately described by the Brooks-Herring screening theory for higher carrier densities. The shape of the band tail of the density of states in Al0.3Ga0.7As is found electrically through transport measurements. It is determined to have a power-law dependence, with an exponent of -1.25 for S1 and -1.38 for S2.

Influence factors on wear resistance of two alumina matrix composites

We measured the wear resistances of alumina, alumina/silicon carbide composite and alumina/mullite composite by abrasive wear. And we studied the influence of fracture mode and worn surface pullout on wear resistance. The results are as follows: the main wear mechanisms of alumina and alumina/silicon carbide were fracture wear and plastic wear respectively, and for alumina/mullite composite, fracture wear and plastic wear mechanisms worked together. The wear resistance of the alumina/silicon carbide composite and the alumina/mullite composite was better by a factor of 1 similar to 3 than that of the monolithic alumina. There were two main reasons for the better wear resistance, i.e., the improved mechanical properties and the more smooth worn surfaces. However, The primary reason was the reduction of area fraction of pullout on the worn surfaces induced by fracture mode transition. (C) 2007 Published by Elsevier B.V.

兔属和盘羊属的分子进化研究

兔属物种的形态特征差异甚微，其分类地位长期存在争议。本研究论文来用线粒体DNA标记从分子水平对兔属物种的系统发育，分类地位以及历史生物地理学进行探讨。我们应用四个线粒体DNA标记：细胞色素b和125基因全序列，ND4和控制区部分序列构建中国野兔和世界范围内的其它兔属物种间的系统发育关系。系统发育关系的构建以鼠兔为外群，采用三种方法：最大简约法（淤），最大似然法（ML）和贝叶斯方法（Bl）。分析结果显示：中国野兔并不是一个单系群。世界范围内的兔属动物形成一个单系，并以地理分布可分为相应的三个种组：北美种组（NortoAmericanspeciesgroup），欧亚种组①urasionspeciesgroP）和非洲种组（S。uthAfricanspeciesgroup）。兔属动物鉴定的29个种可能多于该属的有效种。历史生物地理学的祖先地分析表明：兔属动物起源于北美大陆，通过白令大陆桥扩散到欧亚大陆，最后到达非洲大陆。Brooks简约分析（BPA）揭示兔属物种形成是在扩散事件之后，在不同的地理区域适应当时的生态环境导致种的发生。兔属动物经历了一个快速扩散和种发生的过程。贝叶斯放松分子钟方法估计种组内的分化时间显示：兔属物种的形成是在上新世早期（Plioceneepoch：4.29-5.39MyA）。云南兔（L.comusGAllen1927）是仅分布于云贵高原上的唯一一种兔属物种。我们应用线粒体DNA控制区第一高变区检测云南兔的群体遗传结构和系统地理结构模式，评价地理隔离，如高山、河流等对该物种的群体结构和系统地理模式的影响。分子变异分析显示（AMOVA）不同的地理区域间遗传差异明显，而且成对遗传差异与相应的地理距离成线性关系。错配核普酸分析（Mismatchanalysis）表明云南兔群体近期没有群体扩张。系统地理学的嵌套分析法揭示云南兔现有的群体遗传结构和遗传分化与云南高原复杂的地形地貌相关。高山、河流等地理隔离导致群体间有限的基因流形成了现有云南兔群体的分布。云南兔不同地理区域单倍型的分子系统分析以及明显的群体分化建议云南兔两个亚种的划分（L．c．comusandL．c．peni）。雪兔种组（thetimidusspeciescomplex）是生活于北半球高纬度区域的兔属物种。我们以该种组为模型，采用快速进化的mtDNA控制区序列对它们的系统地理结构进行比较研究。结果表明：雪兔种组以白令海峡为地理隔离存在显著的系变异为7．7％，变异范围从2．4％一11．5％。分子系统分析的最大简约树显示：来自乌孜别克斯坦的两个亚种（seertzoviandnikr枷ontana）首先发生遗传上的分化。之后盘羊祖先群体的扩散导致在中国某些地理区域可能有三个进化谱系的分化。盘羊祖先群体的扩散可能起始于亚洲大陆的西部通过中亚高原向南扩散。分布于中国的盘羊亚种中，阿尔金亚种（O.a.dalai-lamae）与西藏亚种（O.a.hodsoni）有着比蒙古亚种（aa．da附ino较近的系统进化关系。而来自乌孜别克斯坦的两个亚种（servertzoviandnigrimontana）与中国的盘羊亚种有着显著的遗传差异。

Global iron connections between desert dust, ocean biogeochemistry, and climate

IEECAS SKLLQG

土壤持水特征测定中质量含水量、吸力和容重三者间定量关系I.填装土壤

在试验过程中,通常采用一个土样进行连续试验来测定土壤的持水特征。此时,土样的有机质、黏粒矿物类型和阳离子交换量等性质基本保持不变,而土壤的容重在水力学和机械压力共同作用下会发生很大的变化。因此,我们认为实测的土壤持水特征不再是土壤吸力和含水量相对应的一条曲线,而是由土壤质量含水量、吸力和容重三变量共同确定的一个曲面。本文在Brooks-Corey土壤水分特征曲线模型的基础上,提出了两种描述土壤质量含水量、吸力和容重三变量关系的曲面模型,分析了模型的优缺点和适用条件,并采用离心机石蜡控容重法实测了四种质地填装土壤的三变量特征曲面。研究结果表明:土壤持水特征是由土壤质量含水量、吸力和容重三变量共同确定的一个曲面这一假设是合理的;类似于Brooks-Corey模型的两种幂函数经验曲面模型能够合理地描述填装土壤的实测数据,决定系数均大于0.94;模型Ⅰ的拟合效果略好于模型Ⅱ,但模型Ⅱ包含两个物理意义明确的参数,具有一定的优势。这一研究将为校正容重变化对土壤水力学参数的影响提供新的途径。

Benthic foraminifera and bottom water evolution in the middle-southern Okinawa Trough during the last 18 ka

A piston sediment core E017 from the middle-southern Okinawa Trough was investigated. A preliminary study of the deep-water evolution since 18 cal. ka BP was performed based on the quantitative census data of benthic foraminiferal fauna, together with planktonic foraminiferal oxygen and carbon isotope, AMS(14)C dating, and the previous results achieved in the southern Okinawa Trough. The result shows that the benthic fauna was dominated by Bulimina aculeata (d'Orbigny), Uvigerina peregrina (Cushman), Hispid Uvigerina and Uvigerina dirupta (Todd) during the glaciation-deglaciation before 9.2 cal. ka BP, while Epistominella exigua (Brady), Pullenia bulloides (d'Orbigny), Cibicidoides hyalina (Hofker), Sphaeroidina bulloides (d'Orbigny) and Globocassidulina subglobosa (Brady) predominated the fauna in the post-glacial period after 9.2 cal. ka BP. The benthic foraminifera accumulation rate (BFAR), paleoproductivity estimates and benthic foraminiferal assemblage conformably indicate that surface water paleoproductivity and organic matter flux during the glaciation-deglaciation were higher than those of the post-glacial period in the middle-southern Okinawa Trough, and gradually enhanced from the southern to the central Okinawa Trough during the glaciation-deglaciation, which could be caused by the discrepancy of the terrigenous nutrients supply. High abundances of E exigua, an indicator of pulsed organic matter input, after 9.2 cal. ka. BP may indicate that the intensity of seasonally riverine pulsed flux during the post-glacial period was stronger than that of the glaciation-deglaciation period, and the seasonal influx in the central trough might be stronger than in the south. The temporal distributions of the typical species indicating bottom water oxygen content and ventilation condition show that the ventilation of the bottom water during the post-glacial period is more active than the glaciation-deglaciation, which reflects that the evolution of the intermediate and deep waters of the northwestern Pacific during the last glaciation has no evident influence on the deep-water of the middle-southern Okinawa Trough. Additionally, the variations in agglutinated benthic foraminiferal abundance and other carbonate dissolution proxies indicate that carbonate dissolution gradually increased since the last 18 ka in the Okinawa Trough and rapidly enhanced at 9.2 cal. ka BP. The modern shallow carbonate lysocline could form at 3 cal. ka BP.

Ocean urea fertilization for carbon credits poses high ecological risks

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. (C) 2008 Elsevier Ltd. All rights reserved.