澜沧江流域水生昆虫群落分类多样性和功能多样性海拔格局的空间尺度依赖性

群落分类多样性和功能多样性的海拔格局研究, 是了解生物多样性空间分布现状、揭示多样性维持和变化机制的重要途径。当前对水生昆虫分类多样性和功能多样性沿海拔梯度分布格局, 及其尺度依赖性依旧缺乏深入研究。本文基于2013-2018年在云南澜沧江流域500-3,900 m海拔梯度共149个溪流点位的水生昆虫群落调查数据, 利用线性或二次回归模型探索并比较了局部尺度(点位尺度)和不同区域尺度(100 m、150 m、200 m、250 m海拔段)的分类多样性指数(物种丰富度指数、Simpson多样性指数和物种均匀度指数)和功能多样性指数(树状图功能多样性指数(dbFD)、Rao二次熵指数(RaoQ)和功能均匀度指数(FEve))的海拔格局。结果表明, 在局部尺度, 物种丰富度指数和dbFD指数沿海拔梯度均无显著分布特征, Simpson多样性指数、RaoQ指数、物种均匀度指数和FEve指数沿海拔梯度呈现U型或者单调递减趋势。在区域尺度, 随着区域海拔带宽度的增加, 物种丰富度指数沿海拔呈不显著的单调递减格局, 但dbFD指数沿海拔分布由U型转变为单调递减趋势; Simpson多样性指数和RaoQ指数沿海拔梯度由显著U型趋势转变为无显著分布特征; 物种均匀度指数沿海拔梯度无显著分布特征, 但FEve指数呈显著增加的海拔格局。综上, 群落分类多样性指数和功能多样性指数沿海拔梯度分布存在局部和区域尺度的空间差异, 但区域尺度下二者海拔格局随海拔带宽度的增加存在一定程度的一致性。     

Telomere shortening correlates with harsh weather conditions in the bat species Myotis myotis

The relationship of telomere shortening and cellular ageing in cultured cells such as fibroblasts is straightforward: telomeres shorten with an increasing number of cell divisions until they trigger replicative senescence which prevents further mitotic cycles. But studies investigating the relationship between telomere shortening and ageing in whole organisms show contrasting results: while there is a clear decline in telomere length (TL) with chronological age in some species such as humans, no such decline is observed in others. In this issue of Molecular Ecology, Foley et al. (2020) show that experiencing harsh weather conditions correlates with longitudinal telomere shortening in the bat species Myotis myotis, whereas chronological age does not (Foley et al., 2020). Further, the authors investigated whether genetics influence TL and find a low heritability (h² = 0.01–0.06) again suggesting that environmental effects are the dominant drivers of variation in TL in this species. These are important findings as there is disagreement in the literature about the relative magnitude of genetic and environmental effects contributing to TL variation in different species. This paper investigating the impact of environmental effects makes a novel and important contribution to the literature on TL in free‐living mammals.     

Energy–water and seasonal variations in climate underlie the spatial distribution patterns of gymnosperm species richness in China

Studying the pattern of species richness is crucial in understanding the diversity and distribution of organisms in the earth. Climate and human influences are the major driving factors that directly influence the large‐scale distributions of plant species, including gymnosperms. Understanding how gymnosperms respond to climate, topography, and human‐induced changes is useful in predicting the impacts of global change. Here, we attempt to evaluate how climatic and human‐induced processes could affect the spatial richness patterns of gymnosperms in China. Initially, we divided a map of the country into grid cells of 50 × 50 km² spatial resolution and plotted the geographical coordinate distribution occurrence of 236 native gymnosperm taxa. The gymnosperm taxa were separated into three response variables: (a) all species, (b) endemic species, and (c) nonendemic species, based on their distribution. The species richness patterns of these response variables to four predictor sets were also evaluated: (a) energy–water, (b) climatic seasonality, (c) habitat heterogeneity, and (d) human influences. We performed generalized linear models (GLMs) and variation partitioning analyses to determine the effect of predictors on spatial richness patterns. The results showed that the distribution pattern of species richness was highest in the southwestern mountainous area and Taiwan in China. We found a significant relationship between the predictor variable set and species richness pattern. Further, our findings provide evidence that climatic seasonality is the most important factor in explaining distinct fractions of variations in the species richness patterns of all studied response variables. Moreover, it was found that energy–water was the best predictor set to determine the richness pattern of all species and endemic species, while habitat heterogeneity has a better influence on nonendemic species. Therefore, we conclude that with the current climate fluctuations as a result of climate change and increasing human activities, gymnosperms might face a high risk of extinction.     

Repeated measures random forests (RMRF): Identifying factors associated with nocturnal hypoglycemia

Nocturnal hypoglycemia is a common phenomenon among patients with diabetes and can lead to a broad range of adverse events and complications. Identifying factors associated with hypoglycemia can improve glucose control and patient care. We propose a repeated measures random forest (RMRF) algorithm that can handle nonlinear relationships and interactions and the correlated responses from patients evaluated over several nights. Simulation results show that our proposed algorithm captures the informative variable more often than naïvely assuming independence. RMRF also outperforms standard random forest and extremely randomized trees algorithms. We demonstrate scenarios where RMRF attains greater prediction accuracy than generalized linear models. We apply the RMRF algorithm to analyze a diabetes study with 2524 nights from 127 patients with type 1 diabetes. We find that nocturnal hypoglycemia is associated with HbA1c, bedtime blood glucose (BG), insulin on board, time system activated, exercise intensity, and daytime hypoglycemia. The RMRF can accurately classify nights at high risk of nocturnal hypoglycemia.     

Evaluating the DNA barcodes for identification of butterflies from Western Himalayas,Uttarakhand, India

DNA barcodes in species tagging have become a popular tool for taking inventories of species from different groups worldwide. The present study aimed to generate DNA barcodes of butterfly species from the Western Himalayas in Uttarakhand, India. The Indian Western Himalayan region (IWHR) has been explored to a limited extent about butterfly species’ diversity. However, the IWHR is prone to environmental change, and slight variations in climatic conditions can influence species diversity and change butterflies' range. The mitochondrial cytochrome c oxidase I (COI) gene was first used to generate the DNA barcode for butterflies from this region on a broad scale. 28 morphologically identified species, consisting of 102 sequences, were finally grouped into 26 species, with only two species showing ambiguity in species identification. These species had < 3% sequence variations from their neighboring relatives, suggesting cryptic species diversity. Generated sequences were also compared with the GenBank data of conspecific geographical locations, which showed intraspecies variation ranging from 1.3% to 7.3%. It was also noted that butterfly species have both intra and interspecies sequence divergence. In the phylogenetic-based species identification, a total of 28 species belonging to 4 families of butterflies were successfully discriminated, and two species at the genus level, which had high intra-specific divergence (0.025), were considered. However, the high intra-species sequence divergence observed may represent the presence of hidden species.     

Numerical Models for the Simulation of Flexible Artificial Heart Valves: Part I - Computational Methods

Abstract

A numerical model of the coupled motion of a flexing surface in a high Reynolds number flow is presented for the simulation of flexible polyurethane heart valves in the aortic position. This is achieved by matching a Lagrangian dynamic leaflet model with a panel method based flow solver. The two models are coupled via the time-dependent pressure field using the unsteady Bernoulli equation.

Incorporation of sub-cycling in the dynamic model equations and fast pre conditioning techniques in the panel method solver yields efficient convergence and near real-time simulations of valve motion. The generality of dynamic model allows different material properties and/or geometries to be studied easily and interactively. This interactivity is realized by embedding the models within a design environment created using the software IRIS Explorer ^TM.

Two flow domains are developed, an infinite domain and an internal domain using conformal mapping theory. In addition bending stress on the valve is computed using a simple stress model based on spline and circle equation techniques.     

Cell division systems that account for the various arrangements and types of differentiated cells within the secondary phloem of conifers

There are two main types of arrangement of differentiated cells within the radial cell files of secondary phloem in conifer trees. In the C-type arrangement, characteristic of the Cupressaceae, fibre (F), parenchyma (P) and sieve (S) cells are arranged in recurrent groups, such as the “standard” cellular quartet (FSPS). In the P-type arrangement, characteristic of the Pinaceae, there are no fibres and one of the characteristic recurrent arrangements is the cellular sextet (PSSSSS). In addition, in both C-type and P-type arrangements, similar cell types are often organised into tangential bands. A simulation model, based on the theory of L-systems, was devised to account for the determination of these two types of regular and recurrent patterns of differentiated phloem cells. It was based on the supposition that, in the meristematic portion of the phloem domain, there are specific spatio-temporal patterns of periclinal cell division. When new cells are produced, those already present are displaced along the cell file, occupying a predictable number of cellular positions as a result of each round of cell division. Each cellular position is assumed to be associated with a specific value of a morphogen, such as the auxin, indole acetic acid, relevant for vascular differentiation. Using published quantitative data on the distribution auxin across the phloem, and assuming specific threshold values of auxin necessary for the determination of each cell type, it was found that sequences of F, S or P cells developed in accordance with the specific pattern of cell division and the related positional values of auxin experienced by the cells during their displacement through the immediately post-mitotic zone of cell determination. The model accounts not only for the typical C-type and P-type cellular arrangements, but also for certain variant arrangements. It provides a working example of the concepts of positional information and positional value for patterned differentiation within a developing plant tissue. There are similarities between the way groups of phloem cells develop and the differentiation of somites in the embryos of vertebrates.     

Do microbes have macroecology? Large‐scale patterns in the diversity and distribution of marine benthic ciliates

Aim The biogeography and global distribution of protists has long been disputed, with two primary, opposing views. To test these two sets of views in greater detail, we have compiled the available data for marine benthic ciliates and assessed the general patterns of their diversity and distribution compared with Metazoa. Location World‐wide. Methods A comprehensive database (1342 species, over 350 sources) was used to analyse the diversity, distribution, species occurrences and range size distribution of free‐living ciliates that inhabit marine sediments in 17 geographical regions. Results Twenty‐five per cent of the species have been found in a single region only, whereas 18% are widespread (they occur in more than half the regions covering both hemispheres). Only 5–7% of regional faunas are endemic, which is much lower than for macroorganisms. Regional diversity depends neither on total area nor on coastline length and does not show any obvious latitudinal trends, but correlates highly with the investigation effort expended in a region and (negatively) with the average salinity. A comparison of species composition reveals distinctions between the Arctic Area (the White, Barents and Kara seas), Laurasian Area (north Atlantic, north Pacific and European seas), Gondwanian Area (Southern Ocean) and the Antarctic. No clear geographical correlations are found for faunistic composition at the genus or family levels. There is the tendency to narrow the latitudinal ranges for species found at high latitudes (reversal of Rapoport's rule). Main conclusions Undersampling and data insufficiency are the key factors affecting the observed diversity and distribution of microorganisms. Nevertheless, marine benthic ciliates demonstrate certain patterns that generally agree with the ‘moderate endemicity’ model ( Foissner, 2004, 2008 ), but consistently contradict the regularities commonly observed for multicellular taxa. Thus, ciliates do have a biogeography, but their macroecological patterns may be different in some respects from that of macroorganisms.