Genetic variation in two widespread species of salamanders,Taricha granulosa and Taricha torosa

Two species of the genus Taricha are widely distributed. T. granulosa ranges from southern Alaska to central California. T. torosa is comprised of two described subspecies, T. t. torosa, which occupies much of the coast ranges of California, and T. t. sierrae, which inhabits the western slopes of the Sierra Nevada Mountains. A starch gel electrophoretic survey for genetic variation at 34 loci in four population samples of T. granulosa and at 40 loci in five population samples of T. torosa reveals differences among these taxa both in amounts of intrapopulational variability and in patterns of geographic variation. Average observed heterozygosity is 9.6%±0.3% in T. granulosa, 3.3%±0.5% in T. t. torosa, and 7.2%±1.2% in T. t. sierrae. Average numbers of alleles per locus and proportions of polymorphic loci are also highest in T. granulosa, intermediate in T. t. sierrae, and lowest in T. t. torosa. Oregon and California granulosa are genetically nearly as different as the subspecies of torosa, but geographic variation is continuous in the former. T. torosa on the other hand is comprised of three distinct gene pools—T. t. sierrae and northern and southern races of T. t. torosa. Strikingly different amounts of intrapopulational genetic variation and patterns of geographic variation may be explained by steadystate species differences, but historical causes may also exist.This work was supported by AEC Research Contract AT(04-3)34 and NSF Grant GB-42246 to F. J. Ayala and by an NIH predoctoral traineeship administered by the Department of Genetics, U.C. Davis.     

Distribution of Cyprideis torosa (Ostracoda) in Quaternary Athalassic Sediments in Germany and its Application for Palaeoecological Reconstructions

Cyprideis torosa (Jones , 1850) is a very common brackish water ostracod of the German coasts, but, despite empty valves are found occasionally in surface sediments of some modern inland waters, C. torosa could not be found living in modern athalassic waters of Germany so far. During interglacial periods, including the Holocene, however, fossils of this species are quite common in Central Germany, at a distance of more than 300 km away from the coasts of the Baltic and North Seas. All 31 Quaternary localities with C. torosa known so far from Germany are documented. C. torosa is an indicator for brackish waters and widely used as index‐fossil in palaeosalinity reconstructions relying on water chemistry bound morphological changes (nodes, sieve‐pores). The comparisons imply a general underestimation of palaeosalinity in oligo‐ to mesohaline athalassic waters if using nodes and sieve‐pores of C. torosa as proxy. A water chemistry (ionic composition) driven morphological response is assumed instead one by salinity only. Palaeosalinity estimations for athalassic waters, relying on morphological variability alone, should therefore be used with caution. Palaeosalinity trends, however, can be detected. Distinguishing thalassic and athalassic sediments with C. torosa is possible by using the associated ostracod fauna as a discriminator. Regarding the ecology and distribution of C. torosa, permanent, brackish, and shallow water bodies under relatively warm conditions are required for its settlement. The source of the salt are brines originating from Zechsteinian or Triassic underground evaporites. Warm and relatively dry climates could enhance the process for such water bodies of becoming salty, a situation present in Holocene Central Germany. The occurrence of C. torosa can therefore be used for palaeoclimatological studies. The most probable migration path of this ostracod species to athalassic waters is by avian transport. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Plant population and community responses to removal of dominant species in the shortgrass steppe

Question: What are the plant population‐ and community‐level effects of removal of dominant plant species in the shortgrass steppe? Location: The Shortgrass Steppe Long‐Term Ecological Research site in northern Colorado, USA. Methods: We annually measured plant cover and density by species for 10 years after a one‐time aboveground removal of the dominant perennial grass, Bouteloua gracilis. Removal and control plots (3 m × 3 m) were within grazed and ungrazed locations to assess the influence of grazing on recovery dynamics. Our analyses examined plant species, functional type, and community responses to removal, paying special attention to the dynamics of subdominant and rare species. Results: Basal cover of B. gracilis increased by an average of 1% per year, but there was significantly less plant cover in treatment compared to control plots for 5 years following removal. In contrast to the lower cover in treatment plots, the plant density (number of plants m^?2) of certain subdominant perennial grasses, herbaceous perennial and annual forbs, a dwarf shrub, and cactus increased after removal of the dominant species, with no major change in species richness (number of species per 1 m × 1 m) or diversity. Subdominant species were more similar between years than rare species, but dominant removal resulted in significantly lower similarity of the subdominant species in the short term and increased the similarity of rare species in the long term. Conclusions: Removal of B. gracilis, the dominant perennial grass in the shortgrass steppe, increased the absolute density of subdominant plants, but caused little compensation of plant cover by other plants in the community and changes in species diversity.     

The life-cycle of Cyprideis torosa (Crustacea,Ostracoda)

Summary The life-cycle of the dominant brackish water ostracod Cyprideis torosa (Jones, 1850) has been studied during 4 years. The species has only one generation anually. Reproduction is fairly similar throughout the years and appears to be tuned in to temperature. The number of adults has one peak every year and can be described by two exponential functions, one for the increase and one for the decrease. Mortality is very similar every year and approximately constant for months. Cyprideis torosa is on top of the food chain: regulation of numbers is probably not external and may be a function of the past of the habitat. A model is described which permits the evaluation of the duration of development from field data only. Predicted values are in good agreement with observed values.This paper was given as a lecture on the Second International Conference on Meiofauna, York, September 1973     

扎龙湿地藻类优势种生态位及其种间联结性动态分析

为了解扎龙湿地藻类群落结构的季节特征和演替规律,对扎龙湿地藻类群落进行了分析,主要涉及藻类优势度、生态位、MFG功能群划分、生态位重叠值及联结系数分析。结果表明：(1)在检出的8门311种藻类中,夏季种类丰富度最高,全年优势种为狭形纤维藻和啮蚀隐藻。(2)优势种种类和密度季节性差异较大,春季以金藻-绿藻种类为主,夏季以绿藻-隐藻种类为主,秋季以隐藻-绿藻种类为主。(3)生态位宽度值与MFG功能群划分结合分析表明,优势种可分为3个大类别,不同种类对资源利用情况的差异较大,各季节广生态位种能较好的反映扎龙湿地水体环境的季节变化趋势。(4)生态位重叠值在不同季节上有较大差异,O_ik>0.6的占比分别为42.86%(春)、28.57%(夏)和25.00%(秋),表明春季优势种种间资源的竞争最为突出,种间竞争强于夏、秋两季。(5)种间联结性检验结果显示,扎龙湿地藻类优势种间总体联结上呈正关联关系,但是种间联结较为松散,种与种之间相对独立。研究表明,扎龙湿地藻类群落结构生态位测度均存在明显的季节波动,较好反映出水环境季节变化特征,可用来指示湿地水体环境的变化。     

Impact of anthropogenic disturbances on a diverse riverine fish assemblage in Fiji predicted by functional traits

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Life history of peracarid species in South‐western Atlantic: Comparison of population traits between native and exotic species

Life‐history traits of exotic species are important to understand the process involved in their settlement and their potential impact on native biodiversity. In this context, the seasonal density, the population structure and the reproductive patterns of exotic and native peracarid species of two natural marine environments of Southwestern Atlantic were studied in order to determine the traits that favour the invasion success of exotic species. Five samples, consisted of algal patches (0.20 × 0.20 m quadrants), were collected seasonally from 2016 to 2017 in two intertidal environments (La Estafeta and Cerro Avanzado). Both environments presented high richness of cryptogenic and exotic species (Tanais dulongii, Monocorophium insidiosum, Ampithoe valida, Melita palmata and Jassa marmorata), and only two native species were recorded (Apohyale grandicornis and Exosphaeroma lanceolatum). The comparison of life‐history traits suggested that the distribution, dominance and the highest densities of some exotic species are closely related to their continuous reproductive and recruitment periods, their capability to adapt their life‐history strategies to different environmental conditions and to a more efficient distribution of resources during reproduction; however, in native species, only A. grandicornis registered similar life‐history traits than exotic populations, suggesting that their distribution could be limited by a latitudinal gradient. We expect that these results provide essential information to understand the invasion pattern of exotic species and their potential impact on native biodiversity in Southwestern Atlantic.     

Predicting the distribution of a rare species of moss: The case of Buxbaumia viridis (Bryopsida,Buxbaumiaceae)

Buxbaumia viridis is a rare policy species restricted to decaying woods in forests. Although Member States of EU are required to monitor its conservation status, specific models able to predict species distribution are still lacking. However, the availability of such models would strongly improve the efficiency in collection additional data and consequently lead to a better knowledge of its ecology. Aims of this work were (i) to provide a model for species distribution assessing the importance of different environmental variables thought to be important in setting the occurrence of Buxbaumia viridis and (ii) to test the effect of imperfect detection in defining the environmental space where the species occur. With this work, records of B. viridis increased twofold in the Alpine region of Italy, passing from 13 records to 26. We showed that on the Alps, occurrence of Buxbaumia viridis was best predicted by northness, rainfall, canopy closure and necromass. Necromass was the single most important variable. A volume of 48–61 m³/ha of necromass was identified as the threshold value determining the high probability of species occurrence. The imperfect detection probability of the species (p = 0.25), biased towards zero the importance of the environmental variables.     

Detecting host–parasitoid interactions in an invasive Lepidopteran using nested tagging DNA metabarcoding

Determining the host–parasitoid interactions and parasitism rates for invasive species entering novel environments is an important first step in assessing potential routes for biocontrol and integrated pest management. Conventional insect rearing techniques followed by taxonomic identification are widely used to obtain such data, but this can be time‐consuming and prone to biases. Here, we present a next‐generation sequencing approach for use in ecological studies which allows for individual‐level metadata tracking of large numbers of invertebrate samples through the use of hierarchically organised molecular identification tags. We demonstrate its utility using a sample data set examining both species identity and levels of parasitism in late larval stages of the oak processionary moth (Thaumetopoea processionea—Linn. 1758), an invasive species recently established in the United Kingdom. Overall, we find that there are two main species exploiting the late larval stages of oak processionary moth in the United Kingdom with the main parasitoid (Carcelia iliaca—Ratzeburg, 1840) parasitising 45.7% of caterpillars, while a rare secondary parasitoid (Compsilura concinnata—Meigen, 1824) was also detected in 0.4% of caterpillars. Using this approach on all life stages of the oak processionary moth may demonstrate additional parasitoid diversity. We discuss the wider potential of nested tagging DNA metabarcoding for constructing large, highly resolved species interaction networks.     

Implications of reef ecosystem change for the stability and maintenance of coral reef islands

Coral reef islands are among the most vulnerable environments on Earth to climate change because they are low lying and largely constructed from unconsolidated sediments that can be readily reworked by waves and currents. These sediments derive entirely from surrounding coral reef and reef flat environments and are thus highly sensitive to ecological transitions that may modify reef community composition and productivity. How such modifications – driven by anthropogenic disturbances and on‐going and projected climatic and environmental change – will impact reef island sediment supply and geomorphic stability remains a critical but poorly resolved question. Here, we review the unique ecological–geomorphological linkages that underpin this question and, using different scenarios of environmental change for which reef sediment production responses can be projected, explore the likely resilience of different island types. In general, sand‐dominated islands are likely to be less resilient than those dominated by rubble grade material. However, because different islands typically have different dominant sediment constituents (usually either coral, benthic foraminifera or Halimeda) and because these respond differently to individual ecological disturbances, island resilience is likely to be highly variable. Islands composed of coral sands are likely to undergo major morphological change under most near‐future ecological change scenarios, while those dominated by Halimeda may be more resilient. Islands composed predominantly of benthic foraminifera (a common state through the Pacific region) are likely to exhibit varying degrees of resilience depending upon the precise combination of ecological disturbances faced. The study demonstrates the critical need for further research bridging the ecological–geomorphological divide to understand: (1) sediment production responses to different ecological and environmental change scenarios; and (2) dependant landform vulnerability.     

Seasonal variation in the distribution and abundance of Oithona and Oncaea species (Copepoda,Crustacea) in the southeastern Weddell Sea,Antarctica

The coupling between the seasonal distribution of dominant Oithonidae and Oncaeidae and the prevailing environmental conditions in the eastern Weddell Sea was investigated. In samples from February, a community on the shelf and in the oceanic surface layer, consisting mainly of Oithona similis and Oncaea curvata and juveniles of both genera, could be differentiated from a community found in deeper oceanic waters, consisting of Oithona frigida, Oncaea parila, Oncaea antarctica and Oncaea englishi. In November the differences in the species distribution between the two regions were less pronounced and the abundances of all species were much lower than earlier in the year. The dominant species were Oithona similis, which reached abundances of up to 182/m³ in February, and Oncaea curvata with up to 215/m³. Deeper living species were comparatively rare. Oithona similis occurred mainly in the top 200 m during both seasons. The other species, by contrast, were generally deeper and more dispersed through the water column in late winter than in summer.     

长白山高山苔原带蛾类物种组成及其时间动态

长白山高山苔原带环境条件恶劣,通过对高山苔原带蛾类研究,揭示蛾类物种组成以及时间变化,可为研究蛾类对苔原极端生境的适应能力,以及蛾类在维持苔原带生态平衡中的作用提供依据。2005-2007年和2019年,每年的6、7、8月,在长白山高山苔原带利用灯诱采集蛾类标本,分析蛾类的物种组成以及时间动态。共采集蛾类1585头,隶属于13科126种,夜蛾科（Noctuidae）为优势类群,绿组夜蛾（Anaplectoides prasina）和一色兜夜蛾（Cosmia unicolor）为优势种,稀有种较多。蛾类的种-多度分布接近生态位优先假说。7月份蛾类的物种数、个体数最多,丰富度指数、多样性指数都最高,但均匀度指数却最低。不同种类对时间的反应表现出一定的差异,黄绿组夜蛾（Anaplectoides virens）对8月,厉切夜蛾（Euxoa lidia）对6月的适应力相对较强。各物种的顺序日期存在一定的差异性,只有10种蛾类在3个月份都被采集到。研究表明,长白山高山苔原带蛾类的多样性较低,成虫活跃期较短;不同类群的蛾类在苔原环境中显示出差异化的适应性,夜蛾科的适应能力超过其它类群,尺蛾科（Geometridae）的适应性相对较低,蛾类对时间的变化反应比较敏感。     

The genetic dimension of pest pressure in the tropical rainforest

Wet tropical forests are among the most diverse ecosystems on Earth and can host several hundreds of tree species per hectare. To maintain such diversity, the community must contain large numbers of relatively rare species rather than be dominated by a few very common trees, as is often the case in temperate forests. Explaining the mechanisms preventing dominance by common species has been a major task of tropical forest ecology. One of the most promising mechanisms is negative density dependence (NDD) of tree abundance driven by pests, including fungal diseases (‘pest pressure’). NDD entails that the chance of survival of a sapling increases with the distance from a mature tree of the same species, thus preventing species from becoming locally dominant. Curiously, the strength of NDD is negatively correlated with abundance, meaning that tree species that are more common generally show weaker NDD (Comita et al. 2010 ). Interactions between plants and soil pathogens have been shown to play an important role in NDD (Klironomos 2002 ), and rare species are apparently more strongly affected (Mangan et al. 2010 ). However, the genetic mechanisms underlying this phenomenon have remained obscure. In this issue of Molecular Ecology, Marden et al. ( 2017 ) suggest that reduced diversity of the genes involved in pathogen recognition (Resistance genes or R genes) could explain why NDD is stronger in locally rare species.     

Low genetic diversity contrasts with high phenotypic variability in heptaploid Spartina densiflora populations invading the Pacific coast of North America

Species can respond to environmental pressures through genetic and epigenetic changes and through phenotypic plasticity, but few studies have evaluated the relationships between genetic differentiation and phenotypic plasticity of plant species along changing environmental conditions throughout wide latitudinal ranges. We studied inter‐ and intrapopulation genetic diversity (using simple sequence repeats and chloroplast DNA sequencing) and inter‐ and intrapopulation phenotypic variability of 33 plant traits (using field and common‐garden measurements) for five populations of the invasive cordgrass Spartina densiflora Brongn. along the Pacific coast of North America from San Francisco Bay to Vancouver Island. Studied populations showed very low genetic diversity, high levels of phenotypic variability when growing in contrasted environments and high intrapopulation phenotypic variability for many plant traits. This intrapopulation phenotypic variability was especially high, irrespective of environmental conditions, for those traits showing also high phenotypic plasticity. Within‐population variation represented 84% of the total genetic variation coinciding with certain individual plants keeping consistent responses for three plant traits (chlorophyll b and carotenoid contents, and dead shoot biomass) in the field and in common‐garden conditions. These populations have most likely undergone genetic bottleneck since their introduction from South America; multiple introductions are unknown but possible as the population from Vancouver Island was the most recent and one of the most genetically diverse. S. densiflora appears as a species that would not be very affected itself by climate change and sea‐level rise as it can disperse, establish, and acclimate to contrasted environments along wide latitudinal ranges.     

污损性管栖多毛类生态特点及研究展望

污损性管栖多毛类属环节动物门,主要由龙介虫科(Serpulidae)、螺旋虫科(Spirorbidae)、缨鳃虫科(Sabellidae)和蛰龙介科(Terebllidae)4科55种组成,以华美盘管虫(Hydroides elegans)、内刺盘管虫(H.ezoensis)、龙介虫(Serpula vermicularis)和克氏无襟毛虫(Pomatoleios kraussii)等种类为优势种,通常成批的附着在物体表面,严重影响人工设施的安全和性能。污损性管栖多毛类的分布具有明显的地域性和季节性,并与深度有关。今后工作应进一步开展管栖多毛类基础生物学研究,探讨外来种的入侵及影响,丰富和发展生态和分类等方面的研究内容。     

Rare, threatened and alien species in the gastropod communities in the clay pit ponds in relation to the environmental factors (The Ciechanowska Upland, Central Poland)

The objectives of the present survey were to formulate a zoocenological analysis of the gastropod communities in clay pit ponds, as well as to determine the relationships between the gastropods and their environments, and to evaluate the water habitats in terms of their ecological-conservation value. The physical and chemical parameters of water, gastropod species and macrophytes occurring in the ponds indicate mesotrophic conditions. Principal Component Analysis (PCA) reveals a correlation between gastropod density and nitrates, a correlation between gastropod density and alkalinity, and additionally shows a correlation between gastropod density and chlorides. The pond surface area, nitrates, chlorides concentrate, alkalinity, and substratum have all affected these gastropod communities. The occurrence of the first permanent population of Ferrissia clessiniana (Jickeli, 1882) was recorded in Poland. Valvata naticina Menke 1845 has become a critically rare species (CR) due to the pollution of water environments. Five other species, e.g. Anisus vorticulus (Troschel, 1834) and Planorbis carinatus O.F. Müller, 1774 are recorded on the Polish Red List of Species. The clay pit ponds of the Ciechanowska Upland, because of their distinctive environmental features, provide a refuge where a number of rare, threatened and alien gastropod species live.     

Ecological differentiation and habitat unsuitability maintaining a ground beetle hybrid zone

Exogenous selection via interactions between organisms and environments may influence the dynamics of hybrid zones between species in multiple ways. Two major models of a hybrid zone allowed us to hypothesize that environmental conditions influence hybrid zone dynamics in two ways. In the first model, an environmental gradient determines the mosaic distribution at the boundary between ecologically differentiated species (mosaic hybrid zone model). In the second model, a patch of unsuitable habitat traps a hybrid zone between species whose hybrids are unfit (tension zone model). To test these, we examined the environmental factors influencing the spatial structure of a hybrid zone between the ground beetles Carabus maiyasanus and C. iwawakianus using GIS‐based quantification of environmental factors and a statistical comparison of species distribution models (SDMs). We determined that both of the hypothetical processes can be important in the hybrid zone. We detected interspecific differences in the environmental factors in presence localities and their relative contribution in SDMs. SDMs were not identical between species even within contact areas, but tended to be similar within the range of each species. These results suggest an association between environments and species, and provide evidence that ecological differentiation between species plays a role in the maintenance of the hybrid zone. Contact areas were characterized by a relatively high temperature, low precipitation, and high topological wetness. Thus, the contact areas were regarded as being located in an unsuitable habitat with a drier climate, where those populations are likely to occur in patches with limited precipitation concentrated. A comparison of spatial scales suggests that exogenous selection via environmental factors may be weaker than endogenous selection via genitalic incompatibility.     

Geometric morphometrics and leaf phenotypic plasticity: assessing fluctuating asymmetry and allometry in European white oaks (Quercus)

Because plants are unable to move away from unfavourable habitats and environmental perturbations, leaf phenotypic plasticity facilitates light absorption and gas exchange. Oaks (Quercus spp.) are particularly known for their adaptability and plastic phenotypes, and leaf allometry and developmental instability may represent important mechanisms for their adaptation to environments and evolution. Because of its important role in the adaptation of plant populations to different environments, allometry can be involved in diversifying selection. Developmental instability is related to environmental perturbations and stresses by producing random deviations in structures characterized by bilateral symmetry, such as oak leaves. In addition, developmental instability can also arise from genetic bottlenecks or as a result of hybridization. The splitting of symmetric and asymmetric components of variation and their separate analysis allows the variability in leaf shape traits to be summarized, reducing the variation produced by developmental instability. The geometric morphometric approach is a useful method for the study of leaf asymmetry and allometric patterns. This method provides an important tool for the visualization of shape attributes that characterize species with highly variable leaf phenotypic patterns. In this study, leaf shape and size variability of three white oak species was investigated by means of a two‐dimensional landmark‐based method providing improved knowledge of variance partitioning, species discrimination, fluctuating asymmetry and allometric patterns of variation resulting from the different analyses. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 335–348.     

福建敖江口表层沉积硅藻空间分布特征

为探讨福建敖江口表层沉积硅藻空间分布特征,2019年7月对敖江口进行表层沉积硅藻的采样调查,并研究了硅藻与环境因子的关系。结果表明,从13个站点共检出硅藻114种,隶属于39属。硅藻丰度具有从河口向外海先减少后增加的变化特征。聚类分析表明,主要硅藻属种可划分为淡水种组合带和半咸水-咸水种组合带。典型对应分析（CCA）表明,表层海水温度和盐度是影响硅藻分布的主要环境变量。河口区盐度相对较低,主要分布淡水种双面曲壳藻、优美曲壳藻和颗粒沟链藻;外海区北部盐度相对较高,主要分布咸水种流水双菱藻;外海区南部盐度相对较低,主要分布淡水种优美曲壳藻和颗粒沟链藻;滩涂的沉积物较粗,主要分布优美曲壳藻。此外,河口区和外海区南部可能存在一定的水体污染。     

Elevated native terrestrial snail abundance and diversity in association with an invasive understory shrub,Berberis thunbergii,in a North American deciduous forest

Invasive terrestrial plants often substantially reshape environments, yet how such invasions affect terrestrial snail assemblages remains understudied. We investigated how snail assemblages in deciduous forest soils with dense Berberis thunbergii (Japanese barberry), an invasive shrub in eastern North America, differ from forest areas lacking the shrub. Leaf litter and soil samples were collected from forest patches with dense B. thunbergii understories and adjacent control areas within two exurban forest tracts in western Pennsylvania, U.S.A. Snails were identified to species and quantified by standard diversity metrics. Contrary to our expectations, snails were significantly more abundant and diverse in B. thunbergii-invaded areas. Despite differences in abundance, the snail community composition did not differ between invaded and control habitats. The terrestrial snail assemblage we observed, which was composed entirely of native species, appears to respond favorably to B. thunbergii invasion and therefore may not be negatively impacted by physicochemical changes to soils typically observed in association with the plant. Such findings could reflect the fact that B. thunbergii likely creates more favorable habitat for snails by creating cooler, more humid, and more alkaline soil environments. However, the snail assemblages we retrieved may consist mostly of species with high tolerance to environmental degradation due to a legacy of land use change and acid deposition in the region.