Occasional Species Research Articles

Why some ‘inbreeder’ species among mostly outbreeders? conifer examples, a postulate, and research agenda

AbstractBreeding systems vary widely in plants, but mostly cluster towards outbreeding or inbreeding extremes. Conifers, which are woody and generally long-lived perennials, are almost all classical outbreeders, but include occasional species characterised as inbreeders. The latter include some very narrow endemics, but narrow endemics include outbreeders. The inbreeders show high self-fertility, minimal inbreeding depression, typically low DNA polymorphism, and modest functional genetic variation, but self-fertilisation rates can be low. Seven such species are reviewed. It is widely (if often tacitly) assumed that inbreeders arise through severe population bottlenecks. It is proposed, more specifically, that inbreeders could arise through recessive resistance alleles of large effects being expressed, during biotic crises, through some inbreeding in the typically mixed mating systems of outbreeders. Such a crisis might produce not only a population bottleneck but also the conditions for recessive alleles to operate beneficially to make inbreeding advantageous. Avenues for probing the recessive-alleles hypothesis are: quantitative modelling to identify what are plausible conditions, examining genomic signatures of inbreeders, and empirical observation. Appropriate modelling appears challenging, as does seeking informative genomic signatures. Empirical observation, however, may be facilitated by biotic crises promoted by current global migration of pathogens and animal pests.

The native fish diversity with environmental influencing factors in the Daqing River basin, China

IntroductionInvestigating and assessing native fish diversity and conducting regional assessments of threats are vital for the conservation of aquatic biodiversity. For this specific study, the Daqing River basin in China was chosen as the research area. Field surveys were carried out between 2018 and 2019, supplemented by a review of pertinent literature and other records.MethodsTo evaluate fish diversity, the following parameters are selected for analysis: Relative abundance (Pi), Frequency of occurrence (Fi), Margalef richness index (D) , Shannon Wiener diversity index (H′) , and Pielou evenness index (J′).Relative abundance levels are categorized as follows: dominant species make up more than 10%, common species account for 1%–10%, and occasional species constitute less than 1%. Canoco 5.0 software was utilized to conduct Redundancy Analysis (RDA) on the fish species composition and environmental factors at 34 sampling sites.ResultsThe findings revealed that 85 fish species have been recorded in the basin, consisting of 78 freshwater species categorized into 8 orders, 17 families, and 59 genera, among which Cypriniformes comprised 64% of the total catch. The low proportion of threatened and endemic species was an important feature of the fish diversity of the Daqing River. Despite the theoretical presence of 85 species, field surveys managed to collect only 42 species, of which 33 were confirmed as naturally occurring within the basin. The average values of Margalef richness index, 22 Shannon Wiener diversity index and Pielou evenness index were 1.72, 2.04 and 0.80 respectively, signifying a low fish diversity with relatively uniform distribution across the sampled regions.DiscussionThis study found that the community structure and diversity of fish were closely related to environmental factors, particularly water quality. Among these factors, ammonia nitrogen emerged as a significant determinant of fish diversity. High concentrations of ammonia nitrogen inhibit fish growth, endanger health, and can even lead to death. Additionally, dams and other water infrastructure also impact fish community structure and diversity. This baseline study can provide a basis for the protection and ecological restoration of fish resources in the Daqing River.

Diversity of Fish and Decapod Fry in the Coastal Zone of Amvrakikos Gulf

Amvrakikos Gulf and its surrounding coastal lagoons are of primary importance for the local biodiversity and fishing activities. Fish species inhabited the coastal lagoons based on the seasonal ongoing migration movements of fry and adult fish individuals from the sea towards the lagoons. Information on the early stages of fish and decapod species in the Amvrakikos Gulf is limited only to the planktonic ontogenetic stages and reproduction biology, respectively. The aim of this study was to describe the spatial distribution of fry from commercially important fish and decapod species in the coastal zone of Amvrakikos Gulf. The seasonal appearance of the early stage of the most commercially important fish species caught in the coastal zone of the gulf ranged from one to four seasons, depending on the species. Individuals of all ontogenetic stages (fry, juveniles, and adults) were reported for several species (A. boyeri, A. fasciatus, S. abaster, S. tyfle, and B. ocellaris), indicating that these species may be regarded as residents in the coastal zone, providing habitats for their entire life cycle. The average relative abundance of the species/genera exhibited no differences compared to other Greek brackish waters. The species composition in the Amvrakikos Gulf at 10 cm and above was in agreement with the transitional nature of the area, with permanent and occasional species present. The present study emphasizes the importance of the coastal zone as a nursery habitat for commercially important species.

The Structure of Rice Stemborer Assemblages: A Review of Species' Distributions, Host Ranges, and Interspecific Interactions.

This review describes global rice stemborer assemblages based on published species distributions, apparent host preferences, and reported shifts in assemblage composition in response to environmental factors. At least 56 moth (Lepidoptera: Crambidae, Pyralidae, Noctuidae) and fly (Diptera: Diopsidae, Chloropidae) species have been associated with rice; however, only 21 species are of potential, large-scale economic importance with a further 2 species of localized concern; most of the remaining species' associations with rice are based on dubious records without economic impacts on rice production. A list of stemborer-host associations indicates that rice stemborers are largely oligophagous on grasses (Poaceae), but a few species are polyphagous (also attacking Cyperaceae, Typhaceae, and some Eudicotyledon plants). Total stemborer abundance is determined by rice cropping patterns and management. Assemblage species richness is determined by geographical location, surrounding habitat (particularly as regards secondary and occasional species), and season. Evidence suggests that stemborer assemblage structure is largely determined through conditional interspecific competition. Regional assemblages typically include a single dominant lepidopteran species (primary species) that is largely restricted to rice and for which the climate is optimal; one or more secondary species that vary based on the age of rice attacked, rice anatomy, and the proximity to other habitats (including other crops); and occasional species that probably spill over from adjacent grasslands. The co-occurrence of lepidopteran with dipteran rice stemborers requires further research attention.

TRIPS (THYSANOPTERA) ASOCIADOS AL CULTIVO DE ZARZAMORA Y ARÁNDANO EN LOS REYES, MICHOACÁN, MÉXICO

<p><strong>Background. </strong>Different species of thrips are listed as important pests in berries. They cause damage to leaves, flowers and fruits, which cause poor development and deformation of the berry, and loss of production; some species are associated with plant pathogens transmission. <strong>Objectives</strong>. To determine the species of thrips (Thysanoptera) associated with blackberry and blueberry and their seasonal abundance, in the producing region of Los Reyes, Michoacán, Mexico and to determine the most attractive sticky trap color to collect thrips.<strong> Methodology. </strong>The thrips were captured monthly through direct collection on the plants, and with sticky traps (yellow and blue), from April 2021 to August 2022.<strong> Results. </strong>1,615 specimens were obtained, all from Thripidae family, belonging to four genera and six species. <em>Frankliniella</em> and <em>Scirtothrips</em> were the most abundant genera and accounted 96% of the material collected. <em>F. occidentalis</em> was most abundant in blackberry var. Laurita and Elvira, and <em>S. dorsalis</em> in blackberry var. Dasha and blueberry var. Arana. <em>F. bruneri</em> and <em>F. minuta</em> and <em>Plesiothrips ayarsi</em> were first recorded as occasional species, and <em>Neohydatothrips gracilipes</em> as frequent in blackberry var. Dasha and Laurita. The sticky yellow traps caught more thrips. The greater abundance coincided with periods of sprouting and flowering of both crops.<strong> </strong><strong>Implications. </strong>The determination of thrips species that damage berries cultivation and their population fluctuation are fundamental for the implementation of an integrated management program.<strong> Conclusions. </strong>These results enrich the information of the Mexican fauna of Thysanoptera in berries, as well as the attraction to the color of certain traps and seasonal abundance.</p>

Species composition and spatial and temporal distribution of occasional fishes in Haizhou Bay, Shandong, China.

Occasional species are often neglected in community ecology studies due to low abundance and frequence. However, they are closely related to biodiversity maintenance and marine conservation. We used index of relative importance (IRI), distribution center of gravity and Mann-Kendall trend test to elucidate the spatial and temporal distributions and changing trends of occasional fishes in Haizhou Bay based on the fishery resources survey data collected from 2013 to 2019. The occasional fishes in Haizhou Bay was identified based on IRI. Nine of the occasional species were selected to analyze the spatial distribution and interannual trends of relative biomass and occurrence frequency. The results showed that a total of 93 fish species were recorded in the multi-year survey in Haizhou Bay. Among which, 61 species had IRI<10, indicating the existence of a large number of occasional fishes in Haizhou Bay. The nine selected occasional species had distinctive spatial distribution characteristics. Erisphex pottii, Azuma emmnion, and Raja porosa were mainly distributed in the eastern part of Haizhou Bay, with a wide habitat range. Sphyraena pinguis, Coilia nasus, and Zebrias zebra were distributed in the western and southern parts, respectively. The rest species were mainly distributed in the southwestern part. In terms of interannual variation, the biomass and occurrence frequency of Coilia mystus, R. porosa, A. emmnion, and S. pinguis showed fluctuating changes, while Odontamblyopus rubicundus and Ctenotrypauchen microcephalus showed an increasing trend. The biomass and occurrence of Z. zebra, C. nasus and E. pottii gradually decreased with no catch in recent years. This study would contribute to the understanding of the spatial and temporal distribution of occasional species, and provide guidance for the conservation of occasional biological resources and species diversity, especially for the establishment of marine protected areas.

Diversity and distribution variation of urban spontaneous vegetation with distinct frequencies along river corridors in a fast-growing city

River corridors are vital to urban ecology, regulating climate and providing habitats for animals. Spontaneous plants naturally colonize various spaces therein, where they play important roles. Previous studies have explored many factors driving spontaneous plant diversity at the city scale and in specific habitats. However, we lack a holistic understanding of the diversity and distribution of variation of spontaneous vegetation that directly reflects the effects of urbanization. We conducted a field study of 1250 sample plots along river corridors in Chengdu, a fast-growing city in China, and the spontaneous plants in fifteen microhabitat types were surveyed. Diversity and distribution patterns were examined for species with distinct dispersal abilities. There was a far greater richness of occasional species compared to dominant and common species, but occasional species were markedly less abundant. Vacant lots and natural riverbanks harbored the most species, but revetment walls and lawns also supported a considerable number of species, especially in the city center. Species diversity among different urban areas was strongly related to microhabitat conditions. The proportions of dominant, common, and occasional species varied among communities. In communities on vacant lots of less urbanized areas, the richness of dominant species was greater, whereas in green spaces created by planted vegetation, occasional species were more diverse. Green space microenvironments are hospitable to some rare species. Urbanization and microhabitats have co-effects and thus ultimately determine diversity and distribution patterns. Such patterns, if linked to ecological and ornamental value, can provide a new perspective and nature-based solutions to urban rewilding and landscape design.

Unveiling Distribution Patterns and Community Characteristics of Rare and Endangered Plants in the Sanya River Basin, China

Wetlands have an important ecological function and economic value. However, with economic development and urban expansion, wetland plants have suffered serious damage. Rare and endangered plants are “thermometers” that reflect the health processes of their ecosystems. To better protect the wetlands in Sanya, China, we systematically investigated and analyzed the species, quantities, distributions, and community characteristics of the rare and endangered plants in the Sanya River basin using the sample and sample strip methods. We established a total of 152 quadrats, of which 46 contained rare and endangered plants. We identified 27 rare and endangered plants that mainly appeared in the tree and shrub layers. The dominant families and genera of the community were evident. However, the proportion of families and genera with fewer or single species was high, indicating that the species composition of the community is complex, and the plant species diversity is rich. The dominant species in each layer of the community were evident, and the rare and endangered plants are occasional species of the community. The community similarity in the urban areas was high, indicating that the rare and endangered plants in these areas require highly homogenous habitats. The community similarity in the suburbs was low, indicating that the rare and endangered plants in these areas are highly adaptable to different habitats. Threat factors and vegetation coverage degree had a significant impact on the number of species and population size of rare and endangered plants. Finally, according to our study and IUCN classification criteria for the endangered levels, Sonneratia × gulngai meets the CR (Critical Endangered) assessment criteria, thus we recommend upgrading it to the endangered level from VU (Vulnerable).

The bivalves (Mollusca) from Priority Marine Regions in the centre-south of the Mexican Transitional Pacific, associated with the rocky intertidal zone

In Mexico, due to its high biological diversity, use of its resources, and a lack of knowledge about its biodiversity, Priority Marine Regions have been designated. The classification of these regions has served as an instrument for the large-scale conservation because the species composition is relatively homogeneous in these regions. This study reports some ecological attributes of bivalves from the Priority Marine Regions located in the Mexican Transitional Pacific ecoregion. Three samplings have been carried out in 2016–2018 in the rocky intertidal zone. In each sample per site, an area of 10 m2 was covered, and the sampling unit was 1 m2. A total of 4119 specimens were recorded, by identifying 53 species (35 genera, 18 families, and two specimens identified to genus). The richness of the species expected was calculated using non-parametric estimators, by showing acceptable completeness of the inventory. The highest species richness and diversity were recorded in the Copala-Punta Maldonado region (33 species), whereas the highest abundance and density were found in the Colola-Maruata region (30.9 individuals/m2). The best-represented species in abundance and distribution were Chama coralloides, Brachidontes adamsianus, Isognomon janus, and Choromytilus palliopunctatus. By considering their life form and degree of occurrence, studied bivalves attached to a hard substrate (epifaunal species) and restricted to habitats with particular characteristics (occasional species) were the most commonly found. The information provided here is directed to eight Marine Regions designated as a priority for conservation in Mexico, which is important for planning, decision-making, and formulating initiatives aimed at helping to co-ordinate management practice through outreach efforts to the conservation and sustainable use of bivalves as marine resources.

Deverra triradiata Hochst. ex Boiss. from the Northern Region of Saudi Arabia: Essential Oil Profiling, Plant Extracts and Biological Activities.

Devrra triradiata Hochst. ex Boiss is an occasional plant species in the Northern region of Saudi Arabia. The shrub is favored on sandy desert wadis, gypsaceous substrate, and sandy gravel desert. In folk medicine, the plant is used for many purposes; to relieve stomach pains, against intestinal parasites, and for the regulation of menstruation. The present study describes the chemical composition of the essential oils (EOs) of different plant parts of D. triradiata. In vivo and in vitro biological activities of plant extracts and essential oils were also studied. Phenylpropanoids, elemicin (flowers: 100%), dillapiole (Stems: 82.33%; and seeds: 82.61%), and apiol (roots: 72.16%) were identified as the major compounds. The highest antioxidant activity was recorded for the EOs of roots and stems (IC50 = 0.282 µg/mL and 0.706 µg/mL, respectively). For plant extracts, ethyl acetate showed the highest antioxidant activities (IC50 = 2.47 and 3.18 µg/mL). EOs showed high antifungal activity against yeasts with low azole susceptibilities (i.e., Malassezia spp. and Candida krusei). The MIC values of EOs ranged between 3.4 mg/mL and 56.4 mg/mL. The obtained results also showed phytotoxic potential of plant extracts both on the germination features of Triticum aestivum seeds and the vegetative growth of seedlings.

Challenges of applying monophyly in the phylogenetic shallows: taxonomic reappraisal of the Dactylorhiza maculata group

SummaryThe first study of the taxonomically critical European orchid genus Dactylorhiza to use next-generation DNA sequencing generated the statistically best-supported reconstruction of its phylogeny to date. However, the two competing topologies obtained within the monophyletic Section Maculatae differed radically in the placement of the D. maculata s.s.–D. foliosa clade. Both topologies showed D. foliosa to be nested deeply within D. maculata s.s., and suggested that D. saccifera s.l. is paraphyletic, D. saccifera s.s. from south-eastern Europe and Asia Minor diverging before D. gervasiana from south-central Europe (a taxon typically viewed as a subspecies of D. saccifera or, more often, ignored completely). The poorly-sampled but character-rich morphometric comparison presented here suggests that D. saccifera s.s. and D. gervasiana cannot be distinguished with confidence using morphological characters and that, if D. gervasiana is accepted as a species, it is effectively cryptic. The diploid D. foliosa is accepted as an island endemic species, despite rendering paraphyletic the autotetraploid D. maculata s.s.; all other named taxa within the D. maculata s.s. clade are considered infraspecific. Dactylorhiza fuchsii is indisputably a bona fide species rather than a subspecies but it does not merit becoming the basis of a taxonomic section separate from D. maculata s.s. The strongly contrasting degrees of molecular vs morphological disparity reported here are representative of a more general trend evident in groups that have experienced comparatively recent speciation, as is the need to recognise occasional paraphyletic species when circumscribing species by integrating genotypic and phenotypic data categories. Explicit taxonomic criteria combined with a comparative, monographic approach are needed to achieve consistency of ranking. Disproving hypotheses of species status is judged a criminally underrated activity, actually being as important to outcomes as much-vaunted species "discovery".

Determinism and stochasticity in the spatial–temporal continuum of ecological communities: the case of tropical mountains

Ecological communities are assembled in a spatial–temporal continuum. However, we still have a poor understanding of the relative importance of different mechanisms structuring community composition (i.e. beta‐diversity) in space and time. In this study, we start by introducing a conceptual model that capitalizes upon the core‐occasional species concept to predict that the assembly process in tropical mountains is driven by the deterministic turnover of core species in space via habitat sorting, but the turnover of occasional species through time via stochastic events of colonization and local extinctions. We then propose a general analytical framework that allows assessing these predictions by partitioning the total variance of a species‐by‐site‐by‐time matrix (i.e. total beta‐diversity) among its purely spatial (variation in space independent of time), purely temporal (variation in time independent of space) and spatiotemporal (i.e. variation across different sites across different moments in time) components. Through simulation models, we provided theoretical support that the proposed analytical framework is suitable to test the predictions derived from our conceptual model. We then used this framework to identify general patterns and quantify the relative importance of processes underlying the spatial and temporal organization of ten distinct insect metacommunities along a tropical elevational gradient. As predicted, we found that, across taxa, spatial beta‐diversity was mainly explained by environmental variation alone: a pattern that indicates the spatial turnover of core species. In contrast, temporal beta‐diversity could not be distinguished from the expectation of null models where communities are simply represented by random draws from species pools: a pattern that indicates a temporal turnover of occasional species within communities. Taken together, our findings illustrate how our conceptual model and quantitative framework can articulate a better understanding of community assembly in space and time.

ABUNDANCE AND ETHNOMEDICINAL USE OF TREE AND SHRUB SPECIES IN AZAZA AND MOKLA FORESTS IN THE BLUE NILE STATE, SUDAN

Documentation of medicinal plants utilization as an important non-timber forest resources are essential for their restoration and preservation. The present research aims to study the abundance of trees and shrubs in Azaza and Mokla forest in the Blue Nile state and to document their traditional use by two communities of Falata tribe living in the same locality. Field surveys were conducted during the period July-November in 2016 and 2017 following timed-meander survey method. Abundant, frequent, occasional, infrequent, and rare species were estimated. Ethnomedicinal data were collected using semi-structured questionnaires. Documentation was taken from a total of 43 informants. 23 informants from Flata Willa in Amara Seraifa village which is located about 30 Km north of Roseires dam and 20 informants from Falata Odda who are displaced by the dam lake and now resettled in City3 which located south east of the dam lake. A total of 28 medicinal trees and shrubs were identified in the studied forests. The most utilized plant families were leguminosae followed by Malvaceae Apocynaceae, and Zygophyllaceae. The highest proportion of the medicinal plants are trees (68%) and the common treated diseases are stomach pain, respiratory inflammation, haemorrhoid, heart pain, uteritis, anemia, kidney disease, and dysentery. The study recommended further pharmacological and phytochemical research to study the efficiency of these plants to cure the diseases as well as sustainable management approach and proper conservation strategy to be integrated into forest management planning and activities for protection of the studied forests. KEYWORDS: Ethnomedicine; plants; forest; Blue Nile; Sudan

Core and occasional species: A new way forward.

Various methods have been used to divide communities into core species and occasional or satellite species. Some methods are somewhat arbitrary, and there is evidence that many communities are more multimodal than bimodal. They also tend to rely on having multiple years of data.A completely novel method is presented that not only has no requirement for long‐term datasets but can divide communities into multiple groups. It is based on probability a species is present, calculated using Simpson's index and the sequential removal of species from the data.The sequential Simpson's index method was applied to species data from a grassland insect community. It was also applied to eleven other datasets that had been divided into core and occasional species in previously published studies.The new method was found not only to be consistent with previous core–occasional assessments but also able to identify multimodality in species abundance distributions.Although ideally used with a measure of persistence (frequency of occurrence) to rank species, community structure is consistently described even with only species abundance data.The method can be applied to short or long‐term datasets and can help identify multimodality and provide valuable insight into how communities change in time or space.

Community structure of Quercus aliena var acuteserrata forest in the Taibai Mountain, China

Qinling Mountains are biodiversity hotspots in China, with rich vegetation resources and species diversity. To clarify the mechanism underlying biodiversity maintenance during vegetation restoration in this area, we established two permanent plots with each area of 100 m×150 m in the Q. aliena var. acuteserrata secondary forest (SF) and primary forest (PF) in the northern slope of Taibai Mountain in 2016, following the standardized protocols by CTFS (the Center for Tropical Forest Science). We analyzed community composition and structure with measuring all trees with DBH ≥ 1 cm. 2839 and 2840 trees were recorded in the SF and PF plots, respectively. Trees in those two plots belong to 29 families, 45 genera, 65 species and 21 families, 37 genera, 47 species, respectively. The proportions of occasional species and rare species were 38.4% and 24.6% in the SF plot, and 40.4% and 19.2% in the PF plot. Most of the trees were distributed in northern temperate zones, and the proportions of genera were 46.6% and 48.7% in the SF and PF plots, respectively. The diameter of Q. aliena var. acuteserrata in both plots followed a unimodal distribution (more young trees than old ones). The diameter distributions of companion species (e.g., Sorbus alnifolia, Acer davidii, Cornus kousa, and Staphylea holocarpa) were inverted "J" shapes, indicating that those populations could have complete life history. In the pair correlation function g(r) analyses, the aggregation of dominant species were the strongest at 0-2 m scale in the two plots when r=10 m. The degree of aggregation gradually weakened with increasing scale. The population distribution patterns of the dominant species were random or uniform when the scale increased to certain value. The average uniform angle index (W) were 0.56 and 0.58 in the SF and PF, respectively. Trees in the communities followed an aggregated distribution. The average W of the community and dominant species in the SF were smaller than that in the PF, indicating weaker species aggregation in the SF. The average dominance in the SF and PF was both 0.47, indicating that the stands were in a co-dominant state. The average mingling was 0.70 and 0.57 in the SF and PF, respectively, which belonged to high and moderate mingling. Species richness, community stability and spatial distribution patterns of forest community could be affected by human disturbance. The role of interspecific interaction, effects of habitat heterogeneity on species coexistence, and variation of community structure should be considered during vegetation restoration of disturbed forest community.

Flora of Village Excavated Ponds in the Northwest of Yaroslavl Oblast

Excavated ponds are a group of widely distributed small artificial water bodies in the territory of Central Russia. In the countryside, they play an important role as water storage for the irrigation of vegetable gardens, livestock watering, the cultivation of waterfowl, and fire water ponds. In 1998–2014, 49 village excavated ponds located in the northwestern part of Yaroslavl oblast were studied. The inventory of the flora of village ponds revealed 161 species of vascular plants from 44 plant families and 88 genera. The dominant plant families in the flora of such water bodies are Poaceae, Cyperaceae, Asteraceae, Polygonaceae, and Salicaceae; the dominant genera are Carex, Salix, Bidens. The ecotypes of hygrophytes and hygromeso- and mesophytes prevail in the ecological structure of the studied flora. Boreal and plurizonal species are dominant in the geographical structure, and Holarctic and Eurasian species prevail in the regional one. The abundance of plurizonal species among typically aquatic vascular plants, due to a relatively high consistency of the aquatic environment when compared to terrestrial ecosystems, makes flora of village ponds similar to that of other water bodies in the studied area. At the same time, the results of long-term studies make it possible to distinguish such features of flora of these small artificial reservoirs as a large number of occasional plant species not typical for water bodies and extremely high dynamics of their flora in different growing seasons.

Impacts of Saltwater Intrusion on the Fish Assemblage in the Middle Part of Shatt Al-Arab River, Iraq

In 2018, a serious changes in the salinity of the Shatt Al-Arab river, as salinity intrusion progressed further to upper reaches of the river due to sharply decline in river flow. Therefore, the fish assemblage structure in the middle of the river, from Sindbad and Abu Al-Khasibs was assessed during the period from January to December 2018. Fish were sampled by gill nets, cast net and electro-fishing from both sites. Salinity fluctuated from 2.0‰ (January) in both sites to 16.2 and 25.0% during August in both sites, respectively. 35 and 44 fish species were collected from both sites, respectively, these included 18 marine species in first site and 28 marine species in second site. Poecilia latipinna, Tenualosa ilisha and Oreochromis aureus were the dominant species in first site, whereas O. aureus, Carassius auratus and P. latipinna in second site. The index of species richness, diversity and evenness each showed a consistent seasonal pattern in both sites. The highest value of Bray-Curtis similarity index of fish species between both sites was noted during the period of low salinity. Findings indicate that the salinity values and the percentages of marine and occasional species were considerably higher than that documented in the previous studies on this part of the  river.Â

Seasonal Variation in Food Web Structure and Fish Community Composition in the East/Japan Sea

The aim of this study was to assess the temporal variability in the trophic structure of a fish community and the trophic levels of dominant fish species off the eastern coast of Korea. We analyzed the community composition and the stable carbon and nitrogen isotope ratios (δ13C and δ15N) for fish species in Hupo coastal waters over four seasons. Fish assemblages were mainly dominated by resident benthic and benthopelagic fish. In contrast, there were low numbers of pelagic fish, including migrating and occasional species, which varied significantly by season. The fish assemblages generally had relatively wide ranges of δ13C and δ15N (− 21.1 to − 16.3‰ and 10.0 to 14.2‰, respectively), reflecting a clear distinction between resident (mostly benthic or benthopelagic) vs migratory (mostly pelagic) fish. Resident species showed no seasonal differences in their isotopic signatures, whereas pelagic species showed temporal variability in δ13C and δ15N values. The isotopic niche of fish assemblages showed distinctly different patterns between spring–summer and winter–fall with the seasonal changes in the fish community. These patterns might be associated with seasonal variation in the fish community caused by seasonal changes in environmental conditions (e.g., hydrographic parameters and food availability). Our results can offer baseline information/trophic data for ecosystem models that can be used to evaluate the effects of climate on marine ecosystems.

黄淮海平原农业景观非农生境植物功能群特征分析

PDF HTML阅读 XML下载 导出引用 引用提醒 黄淮海平原农业景观非农生境植物功能群特征分析 DOI: 10.5846/stxb201811112439 作者: 作者单位: 河南大学黄河中下游数字地理技术教育部重点实验室;河南大学环境与规划学院,河南大学教育科学学院,河南大学黄河中下游数字地理技术教育部重点实验室;河南大学环境与规划学院,河南大学黄河中下游数字地理技术教育部重点实验室;河南大学环境与规划学院,河南大学黄河中下游数字地理技术教育部重点实验室;河南大学环境与规划学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31600374，41771202），河南省教育厅科学技术研究重点项目（16A180022）；河南省博士后科研项目（2015049） Characteristics of non-agricultural habitat plant functional groups in agricultural landscape of Huanghuaihai Plain Author: Affiliation: Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, Henan University, Kaifeng, China; College of Environment and Planning, Henan University, Kaifeng, China,School of Education, Henan University, Kaifeng, China,Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, Henan University, Kaifeng, China; College of Environment and Planning, Henan University, Kaifeng, China,Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, Henan University, Kaifeng, China; College of Environment and Planning, Henan University, Kaifeng, China,Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, Henan University, Kaifeng, China; College of Environment and Planning, Henan University, Kaifeng, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:植物功能群的划分有助于对生态系统结构、功能和服务的理解与认知，为更好的了解农业景观中残存的各非农生境在区域生物多样性保护和生态系统服务中的地位和作用。在黄淮海平原典型区域布点，对区内主要非农生境（林地、树篱、田间道路、沟渠）中的植物群落进行调查，并基于植物功能群分类结果探讨了其特征和在生态系统服务上的贡献。结果显示：（1）从物种数量来看，双子叶植物占绝对优势，单子叶植物在各生境中均较少，但却具有较高的群落地位，一年生和多年生植物物种丰富度及重要值基本一致；（2）从生境类别来看，田间道路和树篱等生境中一年生和单子叶植物更具有优势，随着人类扰动强度的减弱，在林地和沟渠生境中，开始有大量的多年生物种出现，尽管这些物种多为偶见种。（3）常见种多为一年生双子叶植物，种类不多，但群落地位极高，而偶见种中存在大量的多年生双子叶物种。深入分析认为，在黄淮海平原农业景观中，总体上各非农生境均处于群落演替早期，以一年生和单子叶植物功能群构成了群落主体，群落结构简单，优势种群明显，随着干扰强度的相对降低，林地与沟渠生境中的多年生和双子叶物种大量出现，偶见种增加，优势种地位下降。从物种多样性保护与生态系统服务提供综合考虑的角度看，尽管这些非农生境发挥了重要作用，但所能发挥的作用还很有限，未来仍需进一步减弱人类活动对非农生境的干扰，从而进一步提高区域生态系统服务的总体水平。 Abstract:The Huanghuaihai Plain is one of the most important agricultural landscape areas in China. The division of plant functional groups is conducive to the cognition of ecosystem structure, functions, and services, so as to better understand the status and role of the remaining non-agricultural habitats in the agricultural landscape in regional biodiversity conservation and ecosystem services. In a typical area of the Huanghuaihai Plain, the plant communities in the main non-agricultural habitats (forestland, hedges, field roads, ditches) were investigated. Based on the classification results, the characteristics of plant functional groups in each habitat and their contribution to ecosystem services were discussed. The results showed that (1) in terms of species richness, dicots were dominant, while monocots were less frequent in each habitat but had a higher community status. Species richness and important values of annual and perennial plants were basically the same. (2) From the perspective of habitat categories, annuals and monocots were more dominant in habitats such as field roads and hedges. With less human disturbance, a large number of perennial species start to appear in forest land and ditch habitats, although these species mostly appear only occasionally. (3) The common species are annual dicots, with few species but high community status, and there are a large number of occasional perennial dicot species. Further analysis shows that in the agricultural landscape of Huanghuaihai Plain, most of the non-agricultural habitats are in the early stage of community succession, and the main body of the community is composed of annual and monocot functional groups. The community structure is simple, and the dominant population is clear. With the decrease of disturbance intensity, the perennial and dicot species in the forest and ditch habitats appear in large numbers, and the occasional species increase, while the dominant species declines. From the perspective of comprehensive consideration of species diversity conservation and ecosystem services provision, although these non-agricultural habitats play an important role, their role is still limited. In the future, it is still necessary to further reduce the interference of human activities on non-agricultural habitats, so as to further improving the overall level of regional ecosystem services. 参考文献 相似文献 引证文献

Range extension of a boreal amphipod Gammarus oceanicus in the warming Arctic.

The recent (2008–2016) occurrence of a boreal intertidal amphipod Gammarus oceanicus along the Spitsbergen coast is compared with corresponding data from 1980 to 1994. We aimed to compare the pace of environmental changes in the area (ice retreat, temperature increase) with distribution change of G. oceanicus. Material for the study was collected from intertidal, at low water level from over 100 locations on Spitsbergen, the main island of Svalbard archipelago (expanding from 76 to 80°N). The west coast of the island has been exposed to a steady increase in sea surface and air temperature (2°C in 20 years), as well as a significant decrease in fast ice duration (from over 5 months to less than 1 per year). A total length of more than 3,600 km of the island's coastline has been recently impacted by warming. Of the two sibling Gammarus species that dwell in the Spitsbergen littoral, G. setosus, the local cold water species remains generally where it was observed about 20–30 years ago. By contrast, boreal G. oceanicus has expanded its distribution range by over 1,300 km along the west and north coasts of Spitsbergen and gained dominating position on the number of sites, where it was previously just an occasional species.