scholarly journals Modelling of Individual Species of Phytoplankton in a Lake under Artificial Destratification

1997 ◽  
Vol 41 ◽  
pp. 409-414 ◽  
Author(s):  
Monzur Alam Imteaz ◽  
Takashi Asaeda ◽  
Shuji Takasu
Keyword(s):  
Individual Species ◽  
Artificial Destratification

Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary

1970 ◽  
Vol 28 ◽  
pp. 328-329
Author(s):  
J. R. Ruby ◽  
R. F. Dyer ◽  
R. G. Skalko ◽  
R. F. Gasser ◽  
E. P. Volpe
Keyword(s):  
Germ Cells ◽  
Rana Pipiens ◽  
Comparative Morphology ◽  
Dense Material ◽  
Individual Species ◽  
Microscope Examination ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Cytoplasmic Side ◽  
Intercellular Connections

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.

Modelling ecosystem adaptation and dangerous rates of global warming

2019 ◽  
Vol 3 (2) ◽  
pp. 221-231 ◽  
Author(s):  
Rebecca Millington ◽  
Peter M. Cox ◽  
Jonathan R. Moore ◽  
Gabriel Yvon-Durocher
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Diffusion Rate ◽  
Individual Species ◽  
Genetic Evolution ◽  
Rates Of Change ◽  
Rapid Climate Change ◽  
Warming Climate ◽  
Intraspecies Competition ◽  
High Trait

Abstract We are in a period of relatively rapid climate change. This poses challenges for individual species and threatens the ecosystem services that humanity relies upon. Temperature is a key stressor. In a warming climate, individual organisms may be able to shift their thermal optima through phenotypic plasticity. However, such plasticity is unlikely to be sufficient over the coming centuries. Resilience to warming will also depend on how fast the distribution of traits that define a species can adapt through other methods, in particular through redistribution of the abundance of variants within the population and through genetic evolution. In this paper, we use a simple theoretical ‘trait diffusion’ model to explore how the resilience of a given species to climate change depends on the initial trait diversity (biodiversity), the trait diffusion rate (mutation rate), and the lifetime of the organism. We estimate theoretical dangerous rates of continuous global warming that would exceed the ability of a species to adapt through trait diffusion, and therefore lead to a collapse in the overall productivity of the species. As the rate of adaptation through intraspecies competition and genetic evolution decreases with species lifetime, we find critical rates of change that also depend fundamentally on lifetime. Dangerous rates of warming vary from 1°C per lifetime (at low trait diffusion rate) to 8°C per lifetime (at high trait diffusion rate). We conclude that rapid climate change is liable to favour short-lived organisms (e.g. microbes) rather than longer-lived organisms (e.g. trees).

Disentangling the role of shared ancestry and the environment on leaf stable isotopes

2019 ◽  
Author(s):  
Marko J. Spasojevic ◽  
Sören Weber1
Keyword(s):  
Stable Isotopes ◽  
Environmental Conditions ◽  
Evolutionary History ◽  
Environmental Control ◽  
Phylogenetic Signal ◽  
Individual Species ◽  
Habitat Types ◽  
Δ13c And Δ15n ◽  
Environmental Controls ◽  
Shared Ancestry

Stable carbon (C) and nitrogen (N) isotopes in plants are important indicators of plant water use efficiency and N acquisition strategies. While often regarded as being under environmental control, there is growing evidence that evolutionary history may also shape variation in stable isotope ratios (δ13C and δ15N) among plant species. Here we examined patterns of foliar δ13C and δ15N in alpine tundra for 59 species in 20 plant families. To assess the importance of environmental controls and evolutionary history, we examined if average δ13C and δ15N predictably differed among habitat types, if individual species exhibited intraspecific trait variation (ITV) in δ13C and δ15N, and if there were a significant phylogenetic signal in δ13C and δ15N. We found that variation among habitat types in both δ13C and δ15N mirrored well-known patterns of water and nitrogen limitation. Conversely, we also found that 40% of species exhibited no ITV in δ13C and 35% of species exhibited no ITV in δ15N, suggesting that some species are under stronger evolutionary control. However, we only found a modest signal of phylogenetic conservatism in δ13C and no phylogenetic signal in δ15N suggesting that shared ancestry is a weaker driver of tundra wide variation in stable isotopes. Together, our results suggest that both evolutionary history and local environmental conditions play a role in determining variation in δ13C and δ15N and that considering both factors can help with interpreting isotope patterns in nature and with predicting which species may be able to respond to rapidly changing environmental conditions.

Cumulative degradation in estuaries: contribution of individual species to community recovery

2014 ◽  
Vol 510 ◽  
pp. 25-38 ◽  
Author(s):  
S de Juan ◽  
SF Thrush ◽  
JE Hewitt ◽  
J Halliday ◽  
AM Lohrer
Keyword(s):  
Individual Species ◽  
Community Recovery

Kyiv park "Nivki" and "Teremki" forests and ecological analysis of their habitats

2014 ◽  
Vol 25 (3-4) ◽  
pp. 53-68
Author(s):  
I. V. Goncharenko ◽  
H. M. Holyk
Keyword(s):  
Standard Deviation ◽  
Species Composition ◽  
Human Impact ◽  
Soil Nitrogen ◽  
Beta Diversity ◽  
Plant Cover ◽  
Alpha Diversity ◽  
Light Regime ◽  
Individual Species ◽  
Anthropogenic Pressure

Cenotic diversity and leading ecological factors of its floristic differentiation were studied on an example of two areas – Kyiv parks "Nivki" and "Teremki". It is shown that in megalopolis the Galeobdoloni-Carpinetum impatientosum parviflorae subassociation is formed under anthropogenic pressure on the typical ecotope of near-Dnieper hornbeam oak forests on fresh gray-forest soils. The degree of anthropogenic transformation of cenofloras can be estimated by the number of species of Robinietea and Galio-Urticetea classes, as well as neophytes and cultivars. Phytoindication for hemeroby index may be also used in calculation. We propose the modified index of biotic dispersion (normalized by alpha-diversity) for the estimation of ecophytocenotic range (beta-diversity) of releves series. We found that alpha-diversity initially increases (due to the invasion of antropophytes) at low level of antropogenic pressure, then it decreases (due to the loss of aboriginal species) secondarily with increasing of human impact. Also we found that beta-diversity (differential diversity) decreases, increasing homogeneity of plant cover, under the influence of anthropogenic factor. Vegetation classification was completed by a new original method of cluster analysis, designated as DRSA («distance-ranked sorting assembling»). The classification quality is suggested to be validated on the "seriation" diagram, which is а distance matrix between objects with gradient filling. Dark diagonal blocks confirm clusters’ density (intracluster compactness), uncolored off-diagonal blocks are evidence in favor of clusters’ isolation (intercluster distinctness). In addition, distinction of clusters (syntaxa) in ordination area suggests their independence. For phytoindication we propose to include only species with more than 10% constancy. Furthermore, for the description of syntaxonomic amplitude we suggest to use 25%-75% interquartile scope instead of mean and standard deviation. It is shown that comparative analysis of syntaxa for each ecofactor is convenient to carry out by using violin (bulb) plots. A new approach to the phytoindication of syntaxa, designated as R-phytoindication, was proposed for our study. In this case, the ecofactor values, calculated for individual releves, are not taken into account, however, the composition of cenoflora with species constancies is used that helps us to minimize for phytoindication the influence of non-typical species. We suggested a syntaxon’s amplitude to be described by more robust statistics: for the optimum of amplitude (central tendency) – by a median (instead of arithmetic mean), and for the range of tolerance – by an interquartile scope (instead of standard deviation). We assesses amplitudes of syntaxa by phytoindication method for moisture (Hd), acidity (Rc), soil nitrogen content (Nt), wetting variability (vHd), light regime (Lc), salt regime (Sl). We revealed no significant differences on these ecofactors among ecotopes of our syntaxa, that proved the variant syntaxonomic rank for all syntaxa. We found that the core of species composition of our phytocenoses consists of plants with moderate requirements for moisture, soil nitrogen, light and salt regime. We prove that the leading factor of syntaxonomic differentiation is hidden anthropogenic, which is not subject to direct measurement. But we detect that hidden factor of "human pressure" was correlated with phytoindication parameters (variables) that can be measured "directly" by species composition of plant communities. The most correlated factors were ecofactors of soil nitrogen, wetting variability, light regime and hemeroby. The last one is the most indicative empirically for the assessment of "human impact". We establish that there is a concept of «hemeroby of phytocenosis» (tolerance to human impact), which can be calculated approximately as the mean or the median of hemeroby scores of individual species which are present in it.

FINDING FACTORS OF SURVIVAL THE YOUNG OF MARINE HERRING MIGRATING IN THE NORTHERN PART OF THE CASPIAN SEA

2017 ◽  
pp. 19-25
Author(s):  
Tatiana Stanislavovna Zubkova
Keyword(s):  
First Generation ◽  
Environmental Influence ◽  
Reproductive Capacity ◽  
Individual Species ◽  
Survival Ratio ◽  
The Caspian Sea ◽  
Foraging Area ◽  
Starting Point ◽  
Feeding Assessment ◽  
Predatory Fishes

The objects of research are three species of Caspian migrating herrings (Dolginsk herring ( Alosa brashnikowi ), big-eyed shad ( Alosa saposchnikowii ), Caspian shad ( Alosa caspia caspia )). The work considers two biological aspects of herring reproduction: dependence of number of underyearlings on the number of females in the end of feeding; assessment of survival rate of herring juveniles from the stage of fish egg to the stage of underyearlings. Besides fecundity of individual species, scientists take into account sex ratio in spawning populations, population fecundity, loss of reproductive capacity due to the resorption in unscreened roe. The materials obtained within 2009-2015 show that the dependence of herring underyearling number on the number of females arriving at spawning ground is extremely low. Despite a great number of females on the spawning grounds, the reasons of decreasing number of the first generation can be different: unfavorable hydrological and hydrochemical environment in foraging area, insufficient nutritive base, rescheduling of the spawning etc. The varying number of underyearlings from year to year is more pronounced with predatory fishes: the Dolginsk herring - 2.1 times, big-eyed shad - 1.7 times. The underyearling number of zoo-plankton feeder - Caspian shad is consistently high with minimal yearly variations. The young of Caspian shad have the highest survival ratio (0.0122); the young of predatory herring species the ratio is lower: Dolginsk herring is 4 times less (0.0031), big-eyed shad - 5 times less (0.0024). The data on herring survival from stage of a fish egg to an underyearling stage will become a starting point in the investigation of the environmental influence on to the new herring generations.

Die Brutvogelfauna eines Nadelwaldes der nördlichen Voralpen nach dem Sturm Lothar

2017 ◽  
Vol 168 (2) ◽  
pp. 59-66
Author(s):  
Pierre Mollet ◽  
René Hardegger ◽  
Res Altwegg ◽  
Pius Korner ◽  
Simon Birrer
Keyword(s):  
Forest Succession ◽  
Coniferous Forest ◽  
Bird Species ◽  
Individual Species ◽  
Mountain Forest ◽  
Breeding Bird ◽  
Point Counts ◽  
Federal Institute ◽  
Central Switzerland ◽  
Bird Fauna

Breeding bird fauna in a coniferous forest in the northern Prealps after storm Lothar In a 70-hectare large coniferous forest located on the northern edge of the Alps in central Switzerland, Canton of Obwalden, at an altitude of 1260 to 1550 metres above sea level, we surveyed the local breeding bird fauna in 2002 and 2013 by means of point counts as well as additional area searches for rare species. In December 1999, hurricane Lothar caused two large windthrow areas and several smaller areas with scattered throws in the survey range. We found a total of 48 breeding bird species, which is a very diverse species composition for a mountain forest. In the eleven years between surveys, a decline in distribution or abundance was recorded for four species, while seven species showed an increase; a further four species showed no change. For the remaining species, the data sets were too small to reliably estimate changes. A comparison with forest structure data provided by the Swiss Federal Institute of Forest, Snow and Landscape Research WSL revealed that for five bird species, the changes in distribution or abundance could be explained at least partially by forest succession. In order to obtain realistic distribution and abundance values in this kind of breeding bird survey, it is essential to collect large enough samples and to consider the detection probability of each individual species using appropriate statistical methods.

Orchestrated Flowering and Interspecific Facilitation: Key Factors in the Maintenance of the Main Pollinator of Coexisting Threatened Species of Andean Wax Palms (Ceroxylon spp.)

2020 ◽  
Vol 105 (3) ◽  
pp. 281-299
Author(s):  
Javier Carreño-Barrera ◽  
Luis Alberto Núñez-Avellaneda ◽  
Maria José Sanín ◽  
Artur Campos D. Maia
Keyword(s):  
Conservation Status ◽  
Population Decline ◽  
Floral Biology ◽  
Fruit Production ◽  
Biological Data ◽  
Fruit Yield ◽  
Insect Species ◽  
Individual Species ◽  
Pollination Services ◽  
Flower Visiting

Solitary, dioecious, and mostly endemic to Andean cloud forests, wax palms (Ceroxylon Bonpl. ex DC. spp.) are currently under worrisome conservation status. The establishment of management plans for their dwindling populations rely on detailed biological data, including their reproductive ecology. As in the case of numerous other Neotropical palm taxa, small beetles are assumed to be selective pollinators of wax palms, but their identity and relevance in successful fruit yield were unknown. During three consecutive reproductive seasons we collected data on population phenology and reproductive and floral biology of three syntopic species of wax palms native to the Colombian Andes. We also determined the composition of the associated flower-visiting entomofauna, quantifying the extent of the role of individual species as effective pollinators through standardized value indexes that take into consideration abundance, constancy, and pollen transport efficiency. The studied populations of C. parvifrons (Engel) H. Wendl., C. ventricosum Burret, and C. vogelianum (Engel) H. Wendl. exhibit seasonal reproductive cycles with marked temporal patterns of flower and fruit production. The composition of the associated flower-visiting entomofauna, comprised by ca. 50 morphotypes, was constant across flowering seasons and differed only marginally among species. Nonetheless, a fraction of the insect species associated with pistillate inflorescences actually carried pollen, and calculated pollinator importance indexes demonstrated that one insect species alone, Mystrops rotundula Sharp, accounted for 94%–99% of the effective pollination services for all three species of wax palms. The sequential asynchronous flowering of C. parvifrons, C. ventricosum, and C. vogelianum provides an abundant and constant supply of pollen, pivotal for the maintenance of large populations of their shared pollinators, a cooperative strategy proven effective by high fruit yield rates (up to 79%). Reproductive success might be compromised for all species by the population decline of one of them, as it would tamper with the temporal orchestration of pollen offer.

The resistance of the phenological forms of the common oak (Quercus robur L.) to unfavorable external factors

2017 ◽  
Author(s):  
И.А. Уткина ◽  
В.В. Рубцов
Keyword(s):  
Quercus Robur ◽  
Insect Pests ◽  
Weather Conditions ◽  
External Factors ◽  
Individual Species ◽  
Early Form ◽  
The Common ◽  
Spring Frosts ◽  
Common Oak ◽  
Late Form

Ранняя (Quercus robur var. praecox Czern.) и поздняя (Q. robur var. tardiflora Czern.) фенологические формы дуба черешчатого, выделенные в самостоятельные таксоны в середине XIX в., неоднократно становились объектами исследований для специалистов разного профиля. Собрано немало данных о различиях в их росте, требованиях к условиям местообитания, устойчивости к неблагоприятным внешним факторам. Иногда кроме ранней и поздней феноформ выделяют еще и промежуточные между ними. Наиболее отчетливо различия между феноформами, обусловленные разными сроками листораспускания, проявляются в реакции на поздние весенние заморозки и повреждение листвы насекомыми-филлофагами. Так как на деревьях поздней формы листовые и цветочные почки раскрываются намного позже, чем на ранней, поздняя форма избегает повреждения весенними заморозками. Кроме того, обладая меньшей способностью к формированию летних побегов, она меньше повреждается и ранними осенними заморозками, а также зимними морозами, что способствует образованию у нее более прямых и полнодревесных стволов, по сравнению с ранней формой. Ранняя форма чаще и сильнее повреждается филлофагами ранневесеннего комплекса, у которых отрождение гусениц из яиц синхронизировано с раскрытием почек и распусканием листьев. Есть данные, что видовой состав вредителей листвы на деревьях ранней и поздней форм дуба при их совместном произрастании примерно одинаков, зато численность отдельных видов филлофагов и их соотношение различны. На деревьях ранней формы их больше в несколько раз, что объясняется совпадением фаз развития большинства ранневесенних видов филлофагов и листвы этой формы дуба. Согласно результатам проведенных исследований, поздняя форма предпочтительнее для создания лесных культур дуба как более устойчивая к неблагоприятным погодным условиям и насекомым-вредителям. Early (Quercus robur var. praecox Czern.) and late (Q. robur var. tardiflora Czern.) phenological forms of the common oak, recognized as independent taxa in the mid-nineteenth century, have been subjects of multiple studies by specialists of different fields. Abundant data on the differences in their growth requirements, habitat conditions, and resistance to unfavorable external factors have been collected. Some specialists in addition to early and late phenoforms distinguish intermediate forms. Most clearly the differences between these forms appear in response to late spring frosts and damage of leaves by phyllophagous insects due to different timing of the forms' leafing. As leaf and flower buds in late oaks are revealed much later than in early oaks, late form avoids damage by spring frosts. In addition, due to lower ability to form summer shoots, late oaks are less damaged by early autumn frosts and winter freeze, which contributes to the formation of more straight and full trunks comparing to early oaks. Early oaks are damaged more severely by phyllophagous insects of spring complex, in which hatching of caterpillars from eggs is synchronized with opening buds and unfolding of leaves. There is evidence that species composition of foliage pests on co-occurant early and late forms of oak is nearly the same, but the number of individual species of phyllophagous insects and their ratio are different. In the early form the number of phyllophagous insects is greater by several fold due to concurrence of developmental phases in most early spring phyllophagous species and foliage of this oak form. The obtained results show that the late form of common oak is preferable for forest plantations as more resistant to unfavorable weather conditions and insect pests.

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