Mitochondrial DNA phylogeography of the Labeobarbus intermedius complex (Pisces,Cyprinidae) from Ethiopia

Mitochondrial DNA phylogeography of populations of the Labeobarbus intermedius complex (hexaploid barb) was investigated using 88 complete and 71 partial cytochrome b (cytb) sequences originating from 21 localities in five major drainages in Ethiopia and two localities in northern Kenya. The samples included 14 of the 15 Labeobarbus species described from Lake Tana. Discrete phylogeographic analyses of 159 cytb sequences employing Bayesian Markov Chain Monte Carlo (MCMC) simulations using Bayesian evolutionary analysis by sampling trees (BEAST) supported the monophyly of the L. intermedius complex, including the Lake Tana species. This analysis, in combination with statistical parsimony analysis, identified two mitochondrial DNA lineages within the complex. Divergence dating employing coalescent simulations suggested that the geographic split in the L. intermedius complex that led to the formation of these lineages occurred during the Pleistocene (c. 0·5 M b.p. ), consistent with the timing of volcano‐tectonic events postulated to have shaped the current landscape of East Africa.     

伊犁特克斯河河岸带镰叶锦鸡儿灌丛分株结荚特征

以伊犁特克斯河河岸带阶地和河漫滩两种生境镰叶锦鸡儿(Caragana aurantiaca)灌丛为对象,研究了结荚数量、重量、荚果大小与灌丛分株高度、分枝数量、丛径等指标的关系,探讨了荚果生产过程在种群更新中的作用.结果 表明,阶地中的镰叶锦鸡儿荚果数量、荚果长度和荚果生物量显著高于河漫滩,而有性繁殖分配和单个荚果重显...     

两种生境对四川黄龙沟少花鹤顶兰有性繁殖成功的影响

四川黄龙沟森林和钙化滩流地两种生境中分布着大量的少花鹤顶兰,而且生长在这两种生境中的少花鹤顶兰有性繁殖成功存在着差异,目前尚不清楚这种差异是否是由生境差异所致,及其影响有性繁殖成功的机制。通过对黄龙沟少花鹤顶兰两种生境主要环境因子的调查和两种生境中的花部特征和传粉情况的测量,结果表明森林生境中林木盖度、土壤厚度、土壤含水量、土壤有机质、土壤全氮以及空气相对湿度比钙化滩流地中的高,而灌木盖度、草本盖度、苔藓盖度、空气温度、相对光照强度、土壤温度、全钙以及pH则是钙化滩流地中更高。而两种生境中少花鹤顶兰的形态特征和有性繁殖成功之间也存在明显的差异。在森林生境中的个体与钙化滩流地中的个体相比,最大叶长和最大叶宽更大,花朵数更多,距长也更长,单花和花序寿命更长。但花粉移走率和结实率却是钙化滩流地中的更高。两种生境中温度和光照的差异可能是导致两种生境中少花鹤顶兰花粉移走率和结实率差异的重要原因。     

Abundance Patterns of Landbirds in Restored and Remnant Riparian Forests on the Sacramento River, California, U.S.A.

Riparian vegetation along the Sacramento River—California's largest river—has been almost entirely lost, and several wildlife species have been extirpated or have declined as a result. Large-scale restoration efforts are focusing on revegetating the land with native plants. To evaluate restoration success, we conducted surveys of landbirds on revegetated and remnant riparian plots from 1993 to 2003. Our objectives were to estimate population trends of landbirds, compare abundance patterns over time between revegetated and remnant riparian forests, and evaluate abundance in relation to restoration age. Of the 20 species examined, 11 were increasing, 1 was decreasing (Lazuli Bunting [ Passerina amoena ]), and 8 showed no trend. The negative trend for Lazuli Bunting is consistent with information on poor reproductive success and with Breeding Bird Survey results. There was no apparent guild association common to species with increasing trends. Nine species were increasing on revegetated and remnant plots, four were increasing on revegetated plots only, three were increasing on remnant plots only, the Lazuli Bunting was decreasing on both, and three species were stable on both. Although many species were increasing at a faster rate on revegetated plots, their abundance did not reach that of the remnant plots. For revegetated plots, "year since planting" was a strong predictor of abundance trends for 13 species: positive for 12, negative for 1. Our study shows that restoration activities along the Sacramento River are successfully providing habitat for a diverse community of landbirds and that results from bird monitoring provide a meaningful way to evaluate restoration success.     

Structure of the Murray Valley encephalitis virus RNA helicase at 1.9 Angstrom resolution

Murray Valley encephalitis virus (MVEV), a mosquito-borne flavivirus endemic to Australia, is closely related to Japanese encephalitis virus and West Nile virus. Nonstructural protein 3 (NS3) is a multifunctional enzyme with serine protease and DEXH/D-box helicase domains, whose activity is central to flavivirus replication and is therefore a possible target for anti-flaviviral compounds. Cloning, purification, and crystal structure determination to 1.9 Angstrom resolution of the NS3 helicase of MVEV and characterization of its enzymatic activity is reported. Comparison with the structures of helicases from related viruses supports a possible mechanism of ATP hydrolysis-driven strand separation.     

The Bronze-Age Harappans: A re-examination of the skulls in the context of the population concept

The biometric data on 72 usable adult skulls excavated at Harappa and dated ca. 2500-1700 bc have been re-examined in the light of the genetic concept of “population.” The original study of the material considered separately and independently the various samples from locally differentiated cultural deposits, Cemetery R37, Area G, Cemetery H, etc., and used the typologic concept of racial analysis, a traditional method now sterile. One of the major findings of the study, postulating hypothetical original races, was that a varying proportions of different racial “types” constituted each sample. The present analysis is designed, first, to identify the particular population responsible for the growth of the true Harappan culture and, secondly, to define some selected physical characters of the population. Fifteen variables provided statistical evidence that the pooled remains of Cemetery R37 and Area G can be considered as a sufficiently homogeneous Harappan population. Further, in the absence of statistically significant differences in separate measurements, the entire material may be regarded as representing the Bronze-Age Harappans. Accordingly, some selected cranio-facial features of the population have been described.     

A palynological study of the Acheulian site of Gesher Benot Ya’aqov, Israel

The results are discussed of the palynological (pollen-analytical) examination of a sediment section in the Hula Valley of northern Israel, with evidence of Acheulian occupation dated to 700,000–800,000 b.p. In general there is a fair agreement between the palynological data and the wood remains identified from the site, but there are also discrepancies, some of which can be explained and others not. Although relatively well represented in the pollen record, Pinus (pine) most probably did not occur in the Hula area. Some pollen types are thought to have been carried in from hundreds of kilometres away (long-distance transport). Together the pollen and wood evidence suggests that Quercus ithaburensis–Pistacia atlantica (Tabor oak–Atlantic terebinth) woodland (open forest) was found in the Hula Valley (other than the lake and marshes) and on the lower reaches of the mountains flanking the valley on both sides. In addition to deciduous Tabor oak, evergreen Kermes oak (Quercus calliprinos) must have been an important component of this woodland. Wild olive (Olea europaea var. oleaster) may also have been quite common here. The suggestion of open forest, with fairly widely spaced trees, is based upon the high non-arboreal pollen frequencies and indicates fairly dry climatic conditions. Various stream-bank trees and shrubs are represented in the pollen and/or wood records, such as Fraxinus (ash), Ulmus (elm), Salix (willow) and Platanus (plane tree). During the period represented by the upper section of the pollen diagram, Cedrus (cedar) must have reached the Hula area, indicating increased humidity. In the steppe-like field layer (undergrowth of the woodland) grasses (Gramineae) must have played a prominent role in addition to a great number of other species. In particular Compositae and Umbelliferae include a large variety of species (many different pollen types). Two Chenopodiaceae maxima, coinciding with Gramineae minima, are thought to be indicative of periods of increased climatic dryness. The local lake and marsh vegetation is fairly well represented in the pollen record, but interpretation in terms of vegetation succession is only possible to some degree. Mention is made here of Trapa natans (water chestnut), the nuts of which were consumed by the Acheulian inhabitants. Sytze Bottema: Deceased in 2005.     

Nutrient uptake and gas exchange of Great Basin plants provide insight into drought adaptations and coexistence

植物的养分吸收和气体交换为干旱适应和物种共存带来的启示尽管气候变化很可能会导致干旱生态系统的降水量变化幅度增大,但沙漠灌木群落对降水变化的响应模式尚不清楚。因为适应干旱的植物具有多种生存机制以利于其物种的共存,所以认识沙漠灌木群落对降水变化的响应具有重要的意义。我们在美国大盆地地区(美国加利福尼亚州欧文斯谷)开展了一项同质园实验,对8种干旱适应性植物(其中包括了禾本科植物、灌木和杂类草植物)在3种不同夏季降水 量(分别为每月1.3、2.6和3.9 cm)的响应进行了测定。检测了上述植物在矿物养分吸收(碳、氮、磷、钾、 钙、镁、锰、铜、硼、锌、铁和钠)和气体交换参数(光合速率和气孔导度)方面的变化。研究结果显示, 两种禾本科植物[鼠尾粟草(Sporobolus airoides)和匍匐野麦赖草(Leymus triticoides)]与一种耐盐灌木物种 [密叶滨藜(Atriplex confertifolia)]在水分供给增加时,光合速率和/或气孔导度增加。在这8个物种中,有 5个物种表现出了水分供给与营养物质吸收之间的显著相关性。光合速率更高的三齿蒿(Artemisia tridentata)含有更多的钾、铜和硼,而光合速率更高的北极灯心草(Juncus arcticus)具有更高的镁和铁含量 以及更低的钠含量。北极灯心草以及3种适盐性物种[密叶滨藜、盐草(Distichlis spicata)和鼠尾粟草]在气孔导度和营养素浓度方面表现出了相关性。这些结果表明,干旱适应性物种之间对水分增多情形的生理响应机制的差异以及相关的营养吸收策略可能有助于它们在夏季雨水增多时的相互共存。     

Complex foraging ecology of the red harvester ant and its effect on the soil seed bank

Granivory is an important interaction in the arid and semi-arid zones of the world, since seeds form an abundant and nutritious resource in these areas. While species of the genus Pogonomyrmex have been studied in detail as seed predators, their impact on seed abundance in the soil has not yet been explored in sufficient depth. We studied the impact of the harvesting activities of the ant Pogonomyrmex barbatus on seed abundance in the soil of the Zapotitlán valley, Mexico. We found that P. barbatus activity significantly impacts the abundance of seeds in the soil, which is lower in the sites where P. barbatus forages than it is in sites with no recorded foraging. We also found that P. barbatus distributes intact seeds of three tree species, two of which are nurse plants, and could consequently be promoting the establishment of these species. Using tools derived from graph theory, we observed that the ant-seed interactions exhibit a nested pattern; where more depredated seed species seem to be the more spatially abundant in the environment. This study illustrates the complex foraging ecology of the harvester ant P. barbatus and elucidates its effect on the soil seed bank in a semi-arid environment.