Is local selection so widespread in river organisms? Fractal geometry of river networks leads to high bias in outlier detection

Identifying local adaptation is crucial in conservation biology to define ecotypes and establish management guidelines. Local adaptation is often inferred from the detection of loci showing a high differentiation between populations, the so‐called F_ST outliers. Methods of detection of loci under selection are reputed to be robust in most spatial population models. However, using simulations we showed that F_ST outlier tests provided a high rate of false‐positives (up to 60%) in fractal environments such as river networks. Surprisingly, the number of sampled demes was correlated with parameters of population genetic structure, such as the variance of F_STs, and hence strongly influenced the rate of outliers. This unappreciated property of river networks therefore needs to be accounted for in genetic studies on adaptation and conservation of river organisms.     

秦岭山地松栎混交林主要木本植物组成及更新特征

采用样方法对秦岭南坡中段松栎混交林主要木本植物组成及天然更新特征进行了研究.结果表明:(1)松栎混交林乔木层物种共计40种,油松、锐齿槲栎和华山松为优势种,重要值分别为35.19％、31.99％和8.12％,漆树、栓皮栎和楝木为亚优势种.(2)更新层木本植物共计87种,其中乔木幼苗34种,占总数的39.08％,灌木物种也有一定优势地位,优势种有锐齿槲栎、悬钩子和菝葜等,高度级较小的更新苗在群落内占有较大比例.(3)优势乔木更新特征不同,锐齿槲栎幼苗和幼树密度显著高于油松和华山松,且锐齿槲栎幼苗密度显著高于其幼树,但油松幼苗与幼树、华山松幼苗与幼树间无明显差异.(4)混交林内锐齿槲栎径级结构呈近似倒“J”形分布,种群稳定;油松和华山松种群均呈近似正态分布,大径级个体群相对稳定,但林下幼树不足.该研究结果提示,松栎混交林下油松和华山松更新不良,这将不利于其长期存留于群落中,虽然锐齿槲栎从幼苗到幼树的发育过程中存在更新障碍,但并未影响其种群整体更新,若无大规模干扰,锐齿槲栎将维持逆“J”型的更新方式并成为松栎混交林群落中的第一优势种.     

秦岭南坡油松-锐齿槲栎混交林群落不同层次多样性特征及环境解释

在秦岭山脉南坡陕西省境内设置11个样地进行实地调查,从植物物种组成、多样性指数差异以及多样性指数沿环境梯度排序等方面对该区域油松-锐齿槲栎天然混交林的群落总体以及乔木层、灌木层、草本层的各自4个α多样性指数（Patrick丰富度指数、Simpson优势度指数、Shannon-Wiener多样性指数、Pielou均匀度指数）特征进行分析,以揭示该群落多样性特征及其与环境因素的关系。结果显示：（1）11个样地共记录维管束植物112种,隶属于45科77属,分布较广的物种有蔷薇科、菊科、百合科、松科、禾本科和忍冬科。（2）研究区群落中建群种锐齿槲栎和油松的优势地位突出,乔木层伴生种稀少,平均仅为4.8种,多样性水平较低;灌木层物种组成丰富,平均11.4种;草本层次之,平均9种。（3）单因素方差分析表明,该群落不同层次的多样性指数之间均存在极显著差异（P<0.01）;LSD多重比较及多样性指数变化趋势分析表明,群落多样性水平表现为总体>灌木层>草本层>乔木层。（4）CCA法将群落不同层次多样性指数沿地形因子和土壤养分等12项环境指标梯度的分布划分为界线明显的3个区域,即Ⅰ区（中等浓度土壤磷素和有机质制约区）、Ⅱ区（非环境因子制约区）和Ⅲ区（高浓度土壤磷素制约区）;群落总体多样性主要受灌木层影响,同时也受乔木层均匀度影响,但环境因子对乔木层多样性基本无限制性作用。（5）土壤速效磷、全磷和有机质是造成研究区群落不同层次多样性差异的主要因素,海拔、坡向等地形因子对群落多样性影响不大,可能是由于土壤养分的直接影响削弱了地形因子的间接性生态作用。研究表明：保持中等水平的土壤速效磷（3.775±1.529 mg·kg^-1）和有机质含量［（4.079±1.001）%］,并通过合理补植松栎幼树和伐除枯死木等抚育手段提高乔木层均匀度是维持秦岭南坡油松-锐齿槲栎混交林群落生物多样性的有效措施。     

Comparative analysis of the eye anatomy in fossorial and surface-living skink species (Reptilia: Scincidae), with special reference to the structure of the retina

We compared the eye anatomy of the scotopic fossorial Acontias orientalis, Acontias rieppeli and Typhlosaurus vermis with that of the photopic surface-living Trachylepis punctatissima, with particular reference to the retina. The findings were compared with published data on gecko species (Röll, 2001), to determine whether similar trends existed. The vestigial eye of T. vermis was not comparable with that of the other three skink species. The findings in A. orientalis, A. rieppeli and T. punctatissima were as follows: (a) A. rieppeli lacked a conus papillaris, (b) A. orientalis, A. rieppeli and T. punctatissima were pure-cone species but lacked a fovea, (c) estimated cone density in A. orientalis and A. rieppeli was lower than that in T. punctatissima, (d) the ellipsoid cone segment was smaller and the paraboloid segment larger in A. orientalis and A. rieppeli with the reverse in T. punctatissima, (e) VCL%, ONL%, OPL% and GCL% in A. orientalis and A. rieppeli were significantly greater than that of T. punctatissima, (f) INL% and IPL% in T. punctatissima was significantly greater, and (g) T. punctatissima had abundant Müller cells and fibres. Findings in the gecko species were congruent with those of the three skink species of the present study.     

Plant and soil effects on bacterial communities associated with Miscanthus × giganteus rhizosphere and rhizomes

Bacterial assemblages, especially diazotroph assemblages residing in the rhizomes and the rhizosphere soil of Miscanthus × giganteus, contribute to plant growth and nitrogen use efficiency. However, the composition of these microbial communities has not been adequately explored nor have the potential ecological drivers for these communities been sufficiently studied. This knowledge is needed for understanding and potentially improving M. × giganteus – microbe interactions, and further enhancing sustainability of M. × giganteus production. In this study, cultivated M. × giganteus from four sites in Illinois, Kentucky, Nebraska, and New Jersey were collected to examine the relative influences of soil conditions and plant compartments on assembly of the M. × giganteus‐associated microbiome. Automated ribosomal intergenic spacer (ARISA) and terminal restriction fragment length polymorphism (T‐RFLP) targeting the nifH gene were applied to examine the total bacterial communities and diazotroph assemblages that reside in the rhizomes and the rhizosphere. Distinct microbial assemblages were detected in the endophytic and rhizosphere compartments. Site soil conditions had strong correlation with both total bacterial and diazotroph assemblages, but in different ways. Nitrogen treatments showed no significant effect on the composition of diazotroph assemblages in most sites. Endophytic compartments of different M. × giganteus plants tended to harbor similar microbial communities across all sites, whereas the rhizosphere soil of different plant tended to harbor diverse microbial assemblages that were distinct among sites. These observations offer insight into better understanding of the associative interactions between M. × giganteus and diazotrophs, and how this relationship is influenced by agronomic and edaphic factors.     

FeS2‐Imbedded Mixed Conducting Matrix as a Solid Battery Cathode

A new concept of pairing an active material and a mixed conductor is explored as a solid‐state battery electrode. By imbedding nano‐FeS₂ domains into an amorphous LiTiS₂ matrix, a hybrid power‐energy system is achieved while additionally improving upon many common solid electrode design flaws. High‐resolution transmission electron microscopy is used to probe the active material/mixed conductor interface over the course of cycling. Arguably the most beneficial development is enhancement of charge transfer, manifesting in a significantly increased exchange current as captured in a Tafel analysis. By developing a solution to active material isolation and creating a more homogenous electrode design, cycling at a high rate of C/2 for 500 cycles is obtained. Additionally, the electrode can recover full capacity simply by reducing system rate. Capacity recovery implicates a lack of active material isolation, a common problem in solid‐state batteries.     

Agricultural intensification alters bat assemblage composition and abundance in a dynamic Neotropical landscape

The recent trend of agricultural intensification in tropical landscapes poses a new threat to biodiversity conservation. Conversion of previously heterogeneous agricultural landscapes to intensive plantation agriculture simplifies and homogenizes the landscape, reducing availability, and connectivity of natural habitat for native species. To assess the impact of agricultural intensification on bats, we characterized the bat assemblage in the Sarapiquí region of Costa Rica, where heterogeneous land uses are being converted to intensive, large‐scale pineapple plantations. In 2012 and 2013, we sampled bats in 20 remnant forest patches surrounded by varying proportions of pasture, mature forest, and pineapple and captured 1821 individual bats representing 39 species. We used ordination analyses to evaluate changes in species composition, where pineapple is the main component of the agricultural matrix. We identified landscape metrics specifically correlated with pineapple and used multiple linear regression to test their effects on bat species richness, diversity, and guild‐specific relative abundance. Results suggest pineapple expansion is driving changes in assemblage composition in remnant forest patches, resulting in new assemblages with higher proportions of frugivorous bats and lower proportions of insectivorous bats than in continuous mature forests. In addition, while pineapple does not diminish total bat species richness and diversity, the reduced forest cover and increased distance between forest patches in pineapple plantations has a significant negative impact on the relative abundance of insectivores. We also identify a potential threshold effect whereby patches surrounded by more than 50 percent forest can retain assemblage composition similar to that found in continuous mature forest.     

Thyme travels: 15N isoscapes of Thymus vulgaris L. invasion in lightly grazed pastoral communities

Alterations to ecosystem nitrogen (N) cycling by introduced plant species may increase the invasibility of habitat providing a positive feedback for the introduced species to become invasive. Spatial patterns of foliar and soil δ¹⁵N ratios reflect variation in rates and process of N‐cycling across invaded landscapes and provide insight into N‐source uptake and utilization strategies of invasive plant species. To evaluate invasion‐associated changes in soil and foliar δ¹⁵N at different scales: regional (among different sites), local (between north‐ and south‐facing aspect at the same site), and microsite (within populations in the same community), we measured foliar and soil δ¹⁵ N, animal faeces cover (as a proxy for grazing intensity) and N₂‐fixing species cover from inside to outside Thymus vulgaris L. (thyme)‐invaded lightly grazed pastoral communities in Central Otago, southern South Island, New Zealand. Mean thyme foliar δ¹⁵N were near‐zero across the invaded landscape, and did not change across the advancing edge of invasion or with aspect. There was no evidence that associations with N₂‐fixing species provide a potential N source. Soil δ¹⁵N was lower inside of thyme compared to at the edge or outside of thyme and was varied between aspects at some sites. Animal faeces cover as a proxy for grazing intensity explained only 23% of this observed variation of soil δ¹⁵N. Thyme invasion may result in lowered soil δ¹⁵N reflecting alterations to N dynamics. Associated invasion‐related impacts of animal grazing may also impact soil δ¹⁵N. Further studies are required to distinguish the underlying mechanism responsible for the observed patterns of foliar and soil δ¹⁵N values across thyme‐invaded Central Otago landscapes.