Evidence in hand: recent discoveries and the early evolution of human manual manipulation

For several decades, it was largely assumed that stone tool use and production were abilities limited to the genus Homo. However, growing palaeontological and archaeological evidence, comparative extant primate studies, as well as results from methodological advancements in biomechanics and morphological analyses, have been gradually accumulating and now provide strong support for more advanced manual manipulative abilities and tool-related behaviours in pre-Homo hominins than has been traditionally recognized. Here, I review the fossil evidence related to early hominin dexterity, including the recent discoveries of relatively complete early hominin hand skeletons, and new methodologies that are providing a more holistic interpretation of hand function, and insight into how our early ancestors may have balanced the functional requirements of both arboreal locomotion and tool-related behaviours.     

ECo: A new measure evaluating the degree of consistency between environmental factors and spatial arrangement of species assemblages

We introduce a measure of Environmental Consistency (ECo), which assesses the probability of reducing homogeneity in the environmental factors within a species’ distribution by randomly displacing its occurrences. ECo is computed by applying null model analysis to a species incidence matrix where each locality is associated with a set of environmental values. Environmental homogeneity is measured, for each species, as the average multiparametric distance between any pair of localities where the species occurs. ECo can account for the effect of species interactions and resource availability by using different null models that permit or forbid occurrence displacements altering species local abundance or species prevalence. ECo provides researchers with a flexible statistical framework to address a wide range of ecological and biogeographical issues. We investigated in depth the properties and the potentialities of ECo, showing how it integrates the concepts of Eltonian and Grinnelian niches. We demonstrate that a close relationship exists between niche breadth at species level and environmental consistency of species assemblages. In addition, we provide evidence that ecological consistency is closely related to species range. A software to compute ECo is freely available at http://forest.jrc.ec.europa.eu/download/software/eco.     

The search for stability on narrow supports: an experimental study in cats and dogs

Kinematic and coordination variables were studied in two carnivorans, one with known locomotor capabilities in arboreal substrates (cat), and the other a completely terrestrial species (dog). Two horizontal substrates were used: a flat trackway on the ground (overground locomotion) and an elevated and narrow runway (narrow-support locomotion). Despite their different degree of familiarity with the ‘arboreal’ situation, both species developed a strategy to adapt to narrow supports. The strategy of cats was based on using slower speeds, coupled with modifications to swing phase duration, to keep balance on narrow supports. The strategy of dogs relied on high speeds to gain in dynamic stability, and they increased cycle frequency by reducing swing phase duration. Furthermore, dogs showed a high variability in limb coordination, although a tendency to canter-like coordination was observed, and also avoided whole-body aerial phases. In different ways, both strategies suggested a reduction of peak vertical forces, and hence a reduction of the vertical oscillations of the centre of mass. Finally, lateral oscillation was reduced by the use of a crouched posture.     

Leg muscles that mediate stability: mechanics and control of two distal extensor muscles during obstacle negotiation in the guinea fowl

Here, we used an obstacle treadmill experiment to investigate the neuromuscular control of locomotion in uneven terrain. We measured in vivo function of two distal muscles of the guinea fowl, lateral gastrocnemius (LG) and digital flexor-IV (DF), during level running, and two uneven terrains, with 5 and 7 cm obstacles. Uneven terrain required one step onto an obstacle every four to five strides. We compared both perturbed and unperturbed strides in uneven terrain to level terrain. When the bird stepped onto an obstacle, the leg became crouched, both muscles acted at longer lengths and produced greater work, and body height increased. Muscle activation increased on obstacle strides in the LG, but not the DF, suggesting a greater reflex contribution to LG. In unperturbed strides in uneven terrain, swing pre-activation of DF increased by 5 per cent compared with level terrain, suggesting feed-forward tuning of leg impedance. Across conditions, the neuromechanical factors in work output differed between the two muscles, probably due to differences in muscle-tendon architecture. LG work depended primarily on fascicle length, whereas DF work depended on both length and velocity during loading. These distal muscles appear to play a critical role in stability by rapidly sensing and responding to altered leg-ground interaction.     

Silencing synaptic communication between random interneurons during Drosophila larval locomotion

Genetic manipulation of individual neurons provides a powerful approach toward understanding their contribution to stereotypic behaviors. We describe and evaluate a method for identifying candidate interneurons and associated neuropile compartments that mediate Drosophila larval locomotion. We created Drosophila larvae that express green fluorescent protein (GFP) and a shibire(ts1) (shi(ts1)) transgene (a temperature-sensitive neuronal silencer) in small numbers of randomly selected cholinergic neurons. These larvae were screened for aberrant behavior at an elevated temperature (31-32°C). Among larvae with abnormal locomotion or sensory-motor responses, some had very small numbers of GFP-labeled temperature-sensitive interneurons. Labeled ascending interneurons projecting from the abdominal ganglia to specific brain neuropile compartments emerged as candidates for mediation of larval locomotion. Random targeting of small sets of neurons for functional evaluation, together with anatomical mapping of their processes, provides a tool for identifying the regions of the central nervous system that are required for normal locomotion. We discuss the limitations and advantages of this approach to discovery of interneurons that regulate motor behavior.     

There is no trade-off between speed and force in a dynamic lever system

Lever systems within a skeleton transmit force with a capacity determined by the mechanical advantage, A. A is the distance from input force to a joint, divided by the distance from the joint to the output force. A lever with a relatively high A in static equilibrium has a great capacity to generate force but moves a load over a small distance. Therefore, the geometry of a skeletal lever presents a trade-off between force and speed under quasi-static conditions. The present study considers skeletal dynamics that do not assume static equilibrium by modelling kicking by a locust leg, which is powered by stored elastic energy. This model predicts that the output force of this lever is proportional to A, but its maximum speed is independent of A. Therefore, no trade-off between force and velocity exists in a lever system with spring-mass dynamics. This demonstrates that the motion of a skeleton depends on the major forces that govern its dynamics and cannot be inferred from skeletal geometry alone.     

Positional behavior and canopy use of black snub-nosed monkeys Rhinopithecus strykeri in the Gaoligong Mountains,Yunnan, China

Studies on positional behavior and canopy use are essential for understanding how arboreal animals adapt their morphological characteristics and behaviors to the challenges of their environment. This study explores canopy and substrate use along with positional behavior in adult black snub-nosed monkeys Rhinopithecus strykeri, an endemic, critically endangered primate species in Gaoligong Mountains, southwest China. Using continuous focal animal sampling, we collected data over a 52-month period and found that R. strykeri is highly arboreal primarily using the high layers of the forest canopy (15–30 m), along with the terminal zone of tree crowns (52.9%), medium substrates (41.5%), and oblique substrates (56.8%). We also found sex differences in canopy and substrate use. Females use the terminal zones (56.7% versus 40.4%), small/medium (77.7% versus 60.1%), and oblique (59.9% versus 46.5%) substrates significantly more than males. On the other hand, males spend more time on large/very large (39.9% versus 22.3%) and horizontal (49.7% versus 35.2%) substrates. Whereas both sexes mainly sit (84.7%), and stand quadrupedally (9.1%), males stand quadrupedally (11.5% versus 8.3%), and bipedally (2.9% versus 0.8%) more often than females. Clamber, quadrupedalism, and leap/drop are the main locomotor modes for both sexes. Rhinopithecus strykeri populations never enter canopies of degenerated secondary forest and mainly use terminal branches in the middle and upper layers of canopies in intact mid-montane moist evergreen broadleaf forest and hemlock coniferous broadleaf mixed forests across their habitat.     

Climate–ecosystem modelling made easy: The Land Sites Platform

Dynamic Global Vegetation Models (DGVMs) provide a state-of-the-art process-based approach to study the complex interplay between vegetation and its physical environment. For example, they help to predict how terrestrial plants interact with climate, soils, disturbance and competition for resources. We argue that there is untapped potential for the use of DGVMs in ecological and ecophysiological research. One fundamental barrier to realize this potential is that many researchers with relevant expertize (ecology, plant physiology, soil science, etc.) lack access to the technical resources or awareness of the research potential of DGVMs. Here we present the Land Sites Platform (LSP): new software that facilitates single-site simulations with the Functionally Assembled Terrestrial Ecosystem Simulator, an advanced DGVM coupled with the Community Land Model. The LSP includes a Graphical User Interface and an Application Programming Interface, which improve the user experience and lower the technical thresholds for installing these model architectures and setting up model experiments. The software is distributed via version-controlled containers; researchers and students can run simulations directly on their personal computers or servers, with relatively low hardware requirements, and on different operating systems. Version 1.0 of the LSP supports site-level simulations. We provide input data for 20 established geo-ecological observation sites in Norway and workflows to add generic sites from public global datasets. The LSP makes standard model experiments with default data easily achievable (e.g., for educational or introductory purposes) while retaining flexibility for more advanced scientific uses. We further provide tools to visualize the model input and output, including simple examples to relate predictions to local observations. The LSP improves access to land surface and DGVM modelling as a building block of community cyberinfrastructure that may inspire new avenues for mechanistic ecosystem research across disciplines.     

生态-经济发展情景下内蒙古宏观生态系统模拟与分析

内蒙古自治区是我国北方面积最大、种类最全的生态功能区,是我国北方的重要生态屏障,其宏观生态系统状况不仅关系民众生存和生计,而且关系华北、东北、西北乃至全国的生态安全。构建了1990、2000及2015年3期宏观生态系统格局与影响因子数据集;融合区域生态系统发展规划,设置了基准、生态-经济协同发展和生态-经济权衡发展三种情景;应用土地利用均衡分析模型,模拟了3种情景下2025年及2035年内蒙古六大类生态系统结构与空间格局变化。结果表明：在延续历史发展趋势的基准情景和注重经济发展的生态-经济权衡发展情景下,草地和农田生态系统在2035年均无法恢复至2000年的水平,宏观生态系统结构难以达到规划目标;在注重生态保育的生态-经济协同发展情景下,草地、森林与湿地生态系统面积增长较大,符合内蒙古构建中国北方生态屏障的战略定位。从空间上看,农田生态系统面积的减少主要集中在农牧交错带地区,该区域的退耕还草构成了草地生态系统增加的主要来源;草地生态系统面积扩张还分布在近十年来发生草地退化的区域,这与近年来通过实施"京津风沙源治理"、"草原奖补政策"等生态工程建设后内蒙古自治区原有退化的草地生态系统在逐渐恢复的趋势相吻合;森林生态系统面积增加主要集中分布在大兴安岭等几个植被恢复地;城市生态系统主要以原有城镇居民点为中心,在其周边区域呈扩散式增长,特别是在采矿场、工业用地、交通沿线附近城镇面积增加较为显著;荒漠生态系统的缩减主要发生在与其它生态系统的交界处,这与开发利用的便利性、原有生态系统的可开发潜力等密切相关。研究表明,生态-经济发展情景下的宏观生态系统的空间显性模拟是区域国土空间规划和可持续发展的重要科学依据。