Critical threshold meal size and molt initiation in Rhodnius prolixus

The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus.     

基于InVEST模型的疏勒河流域碳储量时空变化研究

研究区域土地利用方式与生态系统服务碳储量的关系，对于区域生态系统保护及经济社会可持续发展具有重要意义。利用InVEST模型碳储量模块和CA-Markov模型，探究并预测疏勒河流域1990-2015及2015-2040年流域生态系统碳储量时空变化特征及其与土地利用方式之间的关系。结果表明：疏勒河流域1990、1995、2000、2005、2010、2015年碳储量分别为7.994×10⁸、7.996×10⁸、7.998×10⁸、8.038×10⁸、8.064×10⁸、8.071×10⁸t，呈逐年增加趋势，累计增加7.7×10⁶t。土地利用类型变化是导致生态系统碳储量变化的主要因素，未利用地向耕地和草地转化有利于碳储量增加，而草地向耕地和未利用地的转化则导致碳储量减少。疏勒河流域碳储量存在显著的空间格局，碳储量较高区域呈现"北部点状-中部带状-南部点状片状"特征，这种分布格局与流域土地利用类型紧密联系。预测表明至2040年疏勒河流域碳储量为9.128×10⁸t，较2015年增加13.1%，主要原因是草地、耕地和林地面积较大幅度增长，提高了流域内的碳储量。     

Evidence of a genetically distinct population of Vrljika softmouth trout Salmo obtusirostris Heckel evolved by vicariance

Mitochondrial DNA haplotypes (control region, partial cytochrome b and ATPase6 genes) indicate a sister relationship between Vrljika and Neretva softmouth (Adriatic) trout Salmo obtusirostris . This relationship was supported by a tree of individuals based on microsatellite results [allele sharing distances ( D _AS)], which revealed three distinctive clusters, corresponding to Jadro softmouth, Neretva brown trout Salmo trutta and Neretva softmouth trout. Within the latter taxon, Vrljika trout are clearly separated from other trout. The genetic results contradict the synonymy of Jadro with Vrljika softmouth trout, as recently proposed in the Red Book of Freshwater Fish in Croatia. Vrljika softmouth trout appear to have originated from a vicariance that split a common ancestor into large (Neretva) and small (Vrljika) fragmented populations 135 000–270 000 years ago. Vrljika softmouth trout can be distinguished by an array of derived phenotypic and molecular character states. For conservation, this population should be recognized formally at the same taxonomic level as the other geographically separated populations of softmouth trout.     

The method matters: A guide for indicator aggregation in ecological assessments

Ecological assessment requires the integration of many physical, chemical, and/or biological quality elements. The choice of the aggregation method of such partial assessments into an overall assessment can considerably affect the assessment outcome – an issue that has been controversially discussed within the scientific community for the last decade. Current practice often considers only two different aggregation methods, the weighted arithmetic mean (additive aggregation) and the one-out, all-out method (minimum aggregation). However, both have important drawbacks. Additive aggregation compensates a bad status of one quality element by a number of elements featuring good status. Minimum aggregation can lead to overly pessimistic assessment results, since only the quality element in the worst status is considered. Here, we introduce a toolbox containing current and new aggregation methods, demonstrate and discuss their properties with simple, didactical examples, and suggest in which situations best to use them. Then, we illustrate the consequences of selected aggregation schemes for ecological river assessment with the case study of the Swiss Modular Concept of stream assessment (SMC), which we apply to ten river reaches in the Mönchaltdorfer Aa catchment in Switzerland. To be able to do so, we used multi-criteria decision analysis, i.e., multi-attribute value theory, to arrange the SMC quality elements into an objectives hierarchy, and to translate their individual assessments into value functions. Our case study revealed that choosing the most appropriate aggregation method particularly matters, if objectives with significantly different qualities are aggregated. We argue that redundant objectives (i.e., quality elements), often found at the lower levels of the objectives hierarchy, should best be aggregated additively allowing for compensation to increase the statistical significance of the results. Further, we suggest that complementary sub-objectives that often occur at higher levels may be optimally aggregated with a mixture of additive and minimum aggregation. Such a mixed method will allow some compensation, but nevertheless penalize for very bad states. Since here we compare commonly used aggregation methods with some which we believe have never been discussed in an assessment context before, our study concurrently informs ecological assessment in theory and in practice.     

Stream hierarchy defines riverscape genetics of a North American desert fish

Global climate change is apparent within the Arctic and the south‐western deserts of North America, with record drought in the latter reflected within 640 000 km² of the Colorado River Basin. To discern the manner by which natural and anthropogenic drivers have compressed Basin‐wide fish biodiversity, and to establish a baseline for future climate effects, the Stream Hierarchy Model (SHM) was employed to juxtapose fluvial topography against molecular diversities of 1092 Bluehead Sucker (Catostomus discobolus). MtDNA revealed three geomorphically defined evolutionarily significant units (ESUs): Bonneville Basin, upper Little Colorado River and the remaining Colorado River Basin. Microsatellite analyses (16 loci) reinforced distinctiveness of the Bonneville Basin and upper Little Colorado River, but subdivided the Colorado River Basin into seven management units (MUs). One represents a cline of three admixed gene pools comprising the mainstem and its lower‐gradient tributaries. Six others are not only distinct genetically but also demographically (i.e. migrants/generation <9.7%). Two of these (i.e. Grand Canyon and Canyon de Chelly) are defined by geomorphology, two others (i.e. Fremont‐Muddy and San Raphael rivers) are isolated by sharp declivities as they drop precipitously from the west slope into the mainstem Colorado/Green rivers, another represents an isolated impoundment (i.e. Ringdahl Reservoir), while the last corresponds to a recognized subspecies (i.e. Zuni River, NM). Historical legacies of endemic fishes (ESUs) and their evolutionary potential (MUs) are clearly represented in our data, yet their arbiter will be the unrelenting natural and anthropogenic water depletions that will precipitate yet another conservation conflict within this unique but arid region.     

A study of natural populations of the celery leaf-miner,Philophylla heraclei L. (Diptera,Tephritidae) II. Importance of changes of mines for larval populations

The leaf-mining larvae of the celery fly, P. heraclei, have the ability to leave their primary mine to bore a secondary mine in another leaflet or leaf. This phenomenon is always numerically significant under natural conditions (depending on the plots and the years, 38 to 97% of the larvae observed made such a change), although it is not an obligatory behavior. The distribution of the secondary mines on the leaflets and on the leaves varies with the importance of the migrations, with the total unoccupied and healthy leaf area and with the relative position of different leaves on the plant. These migrations are due to the insufficiency of healthy food available for the larvae: either because the quantity of parenchyma offered by a leaflet is too small for a larva, or because there is intraspecific competition following multiple egg-layings on the same leaflet, or because there is a deterioration of the quality of the parenchyma, particularly following the development of celery leaf-spot. The possibility for the larvae of P. heraclei to bore secondary mines appears to be an extremely important factor in the population dynamics of this species. This permits the reduction of the negative effects of intraspecific competition and celery leaf-spot, and permits the colonization by the larvae of young leaves not used by the females at the time of egg-laying.     

Fluorescence characterization and microbial degradation of dissolved organic matter leached from salt marsh plants in the Yellow River Delta

盐沼植被是沿海水体中溶解有机物(Dissolved Organic Matter, DOM)的重要贡献者。然而,不同盐沼植物释放DOM的动力学特征尚缺乏系统研究和比较。黄河三角洲湿地是中国东海岸面积最大,保护最完善的沿海生态系统之一。本论文研究了2016年10月从黄河三角洲(Yellow River Delta, YRD)盐沼中采集的三种常见沼泽植物(芦苇(Phragmites australis),碱蓬(Suaeda salsa)和獐茅(Aeluropus littoralis)的DOM释放过程。通过测定溶解有机碳(Dissolved Organic Carbon, DOC)和溶解氮(Dissolved Nitrogen, DN)发现,植物叶片释放的DOM浓度远高于其根和茎。在27天的培养期内,平均有15%的生物碳和30%的生物氮以DOC和DN的形式通过植物叶片释放。从植物中释放的DOM非常不稳定,在27天的培养期内,细菌共消耗了92.4%–98.1%的DOC和88.0%–94.6%的DN。植物释放DOM的荧光特性表明,发色溶解的有机物(Chromophoric Dissolved Organic Matter, CDOM)是DOM的主要组分,而类蛋白组分是植物释放CDOM的主要组分。细菌的降解作用改变了DOM的荧光性质和化学组成。上述的室内研究结果得到了实地调查的充分支撑,表明在深秋时期黄河口湿地有大量DOM溢出。本研究结果表明,盐沼植物释放的DOM是沼泽和沿海水域DOC和DN的重要来源,而且易降解DOC和DN为黄河口湿地和邻近沿海水域中的微生物群落提供了重要的食物来源。     

长江三角洲核心区绿地系统时空演变特征及生态服务价值评估

在经济建设与环境保护矛盾突出的背景下,研究区域绿地系统时空演化特征,探讨人为因素对绿地系统生态服务的影响,对于改善绿地资源管理、促进区域永续协调发展具有重要意义。本研究基于景观生态学研究方法和生态服务价值当量因子评估法,运用ArcGIS 10.2软件的空间分析功能,对1990-2015年长江三角洲核心区绿地系统时空演化特征及生态服务价值进行了分析。结果表明:(1)长三角核心区绿地景观规模随时间的变化具有阶段性特征,呈现先扩大后缩减的态势;绿地景观与其他土地利用类型的转移存在阶段性与指向性特征;绿地景观格局总体上表现为初期集聚同质化、后期破碎异质化。(2)长三角核心区绿地系统生态服务价值随时间变化明显,不同绿地景观类型有不同的阶段性特征;长三角核心区绿地系统生态服务类型中,调节服务对于绿地系统整体生态服务价值贡献最大。(3)长三角核心区绿地系统生态服务价值在空间上呈现南北不均衡的特征,总体上呈南高北低态势,其中杭州市绿地系统生态服务价值在不同阶段均最高。区域地形地貌是影响区域生态服务价值的一个重要因素。