Early thalamocortical tract guidance and topographic sorting of thalamic projections requires LIM-homeodomain gene Lhx2

The thalamocortical tract is the primary source of sensory information to the cerebral cortex, but the mechanisms regulating its pathfinding are not completely understood. LIM-homeodomain (LIM-HD) gene Lhx2 has been proposed to participate in a combinatorial "code" to regulate dorsal thalamic patterning and also the topography of thalamocortical projections. Here, we report that Lhx2-/- embryos exhibit a gross disruption in the early development of the thalamocortical tract, such that thalamic axons are unable to enter the ventral telencephalon. A possible cause for this deficit is a severe reduction of "pioneer" cells in the mutant ventral telencephalon that constitutes a putative mechanism for guiding the entry of the thalamocortical tract into this structure in vivo. However, in vitro, the thalamocortical tract is able to enter the ventral telencephalon, and this permitted an examination of whether thalamocortical topography is normal in the Lhx2 mutant. Contrary to hypotheses that proposed a cell-autonomous role for Lhx2 in the thalamus, Lhx2-/- thalamic explants generate a normal topography of projections in control ventral telencephalic preparations. This is consistent with our findings of normal patterning of the Lhx2 mutant dorsal thalamus using a wide array of markers. In the reverse experiment, however, control thalamic explants display aberrant topography in Lhx2-/- telencephalic preparations. This perturbation is restricted to projections from caudal thalamic explants, while rostral and middle explants project normally. Thus Lhx2 is required for multiple steps in thalamocortical tract pathfinding, but these functions appear localized in the ventral telencephalon rather than in the dorsal thalamic neurons. Furthermore, the absence of Lhx2 in the ventral telencephalon selectively disrupts a subset of thalamic axon topography, indicating a specific rather than a general perturbation of cues in this structure.     

委内瑞拉东南加勒比海岸七种海洋鲸类的潜在地理分布

本研究阐述了委内瑞拉沿海最常见的海洋鲸类的潜在地理分布情况。通过GIS分析,鲸类分布与地形和深度是相反的,以此可以获得鲸类潜在的分布图。已报告确认了16个物种(有402个目击报告),其中小布氏鲸(Balaenoptera edeni)、座头鲸(Megaptera novaeangliae)、海豚(Delphinus spp.)、圭亚那侏型豚(Sotalia guianensis)、花斑原海豚(Stenella frontalis)、长吻原海豚(Stenella longirostris)和宽吻海海豚(Tursiops truncatus)是最常见的。小布氏鲸和宽吻海海豚有可能分布于整个海岸,包括江河区域。座头鲸则可能季节性地集中分布在大陆架上的海岛沿岸和浅水区域。海豚(Delphinus spp.)有可能分布于高边坡区或沿海上升流区。花斑原海豚可能分布在东北区的西部,中部沿海以及与委内瑞拉海岸平行的岛屿周围。长吻原海豚则分布于浅海和远海区域。在一些高产的生态系统内新的物种可能正在形成,而这些潜在可能的分布图可以作为在高产生态系统内确立关键栖息地的标准,由此我们可以在委内瑞拉水域为鲸类建立新的保护区。     

Assessing regional scale habitat area with a three dimensional measure

A method of measuring the three-dimensional (3D) area of habitats across a regionally complex cultural landscape is described. It is based on overlaying field mapped habitats from sample grid squares onto a digital terrain model of topography constructed using triangulated irregular networks to calculate a terrain corrected area (3D area). The method is suitable for regional-scale ecological studies and has the potential to be used to determine habitat metrics other than area that are sensitive to dimensionality. It is pragmatic with currently available software. The extent to which the area of habitats is underestimated by a two-dimensional (2D) area measure, compared with a 3D measure, is assessed. There was a significantly greater 3D area of all habitat types. The 2D to 3D area increase was especially large in specific seminatural habitats associated with topographic complexity and agricultural land use constraints. They included European Priority Habitats of high conservation value such as dry heath and calcareous grassland. This is of direct relevance for assessing area-based biodiversity evaluation criteria. The economic consequences of 3D area adjustments to production subsidies for agricultural habitats and agri-environment scheme payments were large if applied at a regional scale, especially in marginal upland and upland farms.     

一种作物种植的气候适应性模糊综合评价方法的探讨

提出了一种作物种植的气候适应性的模糊综合评价方法．作物种植的气候适应性可定义为一定地理环境下,其自然气候条件能满足作物生长所需适宜气候条件的能力．在相同的地理环境下,作物种植的气候适应性因作物种类不同而表现不一,并可表示为该地理环境提供的自然气候条件对不同作物生长所需适宜气候条件的满足程度．作物种植的气候适应性的模糊综合评价包括以下主要步骤：确定影响作物种植的主要气候因子,确定各因子的权重,建立评价因子集并确定气候因子评价标准、建立评价矩阵和计算作物生长气候适应性等.采用该方法对武夷山北坡不同海拔高度柑桔和茶树种植的气候适应性进行了综合评价．     

Using topographic networks to build a representation of consciousness

The subject of consciousness has intrigued both psychologists and neuroscientists for many years. Recently, following many recent advances in the emerging field of cognitive neuroscience, there is the possibility that this fundamental process may soon be explained. In particular, there have been dramatic insights gained into the mechanisms of attention, cognition and perception in recent decades. Here, simple network models are proposed which are used to create a representation of consciousness. The models are inspired by the structure of the thalamus and all incorporate topographic layers in their structure. Operation of the models allows filtering of the information reaching the representation according to (1) modality and/or (2) sub-modality, in addition several of the models allowing filtering at the topographic level. The models presented have different structures and employ different integrative mechanisms to produce gating or amplification at different levels; the resultant representations of consciousness are discussed.     

Expansion of bamboo forests caused by reduced bamboo-shoot harvest under different natural and artificial conditions

To elucidate the expansion of bamboo (Phyllostachys pubescens Mazel ex Houzeau de Lehaie) forests, we used multiple linear regression analysis and determined whether there were site differences for data obtained in Hirasawa, Otaki-machi, Chiba Prefecture, and Kofuki, Takehara City, Hiroshima Prefecture, Japan. Vegetation maps from 1984 and 2001 for Hirasawa, and from 1986, 1996, 2000, and 2006 for Kofuki, were compared, and the annual expansion rate of each P. pubescens forest was calculated. We evaluated nine indices, including original bamboo forest area, neighbouring vegetation, slope inclination and aspect, distance from roads, and shipment of bamboo shoots. Shipment of bamboo shoots was a positive factor for P. pubescens forest expansion, whereas the proportion of adjacent short vegetation, northness (the cosine of slope aspect), and area negatively affected the expansion in Hirasawa (R ² = 0.683). On the other hand, distance from roads and eastness (the sine of slope aspect) positively affected expansion, while slope inclination was a negative factor in Kofuki (R ² = 0.942). We calculated that P. pubescens forests expanded at about 2% per year in regions of reduced shipments of bamboo-shoot harvest. We showed that not only natural conditions but also management factors affect P. pubescens forest expansion. Regional differences in natural and anthropogenic effects on expansion were also found.     

Influence of topography on the location and density of armadillo burrows (Dasypodidae: Xenarthra) in the central Amazon, Brazil

Armadillos (Dasypodidae: Xenarthra) are the principal group of burrow-excavating mammals in Amazonian forest. Little is known about how the landscape's physical characteristics influence where these organisms choose to construct their burrows. We measured topographic characteristics of armadillo burrow placement and evaluated whether these variables affect overall burrow density. Our study took place on the study sites of the Biological Dynamics of Forest Fragments Project in the central Amazon, Brazil. To determine if armadillos exhibit habitat use preferences in constructing their burrows, we quantified the declination and elevation of available terrain along transect lines on our study sites and compared this with the characteristics of areas containing burrows. We also tested whether topographic variables were related to burrow density. Armadillos preferentially build burrows on low elevation, inclined terrain, and declination was positively related to burrow density. Low, inclined areas correspond to slopes next to stream basins. It may require less effort for armadillos to excavate these areas, while also providing proximity to water. The results of this study indicate that topographic information is important to consider when using burrows to estimate habitat use and density of armadillos in terra-firme forests of the central Amazon.     

Patterns of plant species richness in Alpine hay meadows: Local vs. landscape controls

Habitat type and quality are recognised as important local determinants of species richness, but other processes operating at the landscape scale can also affect diversity patterns. The evidence regarding the relative importance of landscape context on vascular plants is diverse, and little is known about the effects of this complex factor in Alpine environments. Hence, the primary purpose of the study was to elucidate the relative effects of the determinants of plant species richness by decomposing the variation into local and landscape components. We sampled 99 hay meadows in the Italian Alps, and recorded 14 explanatory variables ascribed to three sets: two sets of local variables, meadow management and abiotic environment, and a set of landscape variables. Plant diversity was affected primarily by local determinants. Species richness tended to increase in less fertilised meadows, confirming the detrimental effect of intensive meadow management on plant diversity. Site conditions such as steep slopes also enhanced plant species richness, showing a most pronounced positive effect in meadows that were cut less frequently. As to the landscape determinants, a high proportion of urban elements affected species richness negatively probably due to further eutrophication. In contrast, an increased length of meadow edges had a positive effect, particularly in meadows located on shallow soils. Partitioning analyses revealed that the three sets of variables showed relatively large shared effects with each other (over half of the total variation explained). In conclusion, the composition of the surrounding landscape had a lower impact on vascular plant species richness than did meadow management and local abiotic environment.