Ecological differences among Chilean populations of commercialGracilaria

Field farming ofGracilaria is gradually replacing use of the wild crop in Chile. The most popular planting method consists of establishing underground thallus systems for patches ofGracilaria on wave-sheltered, soft-bottom habitats. Commercial cultivation often involves transplanting vegetative material to distant places along the coast. This study shows that native populations possess some ecological differences that might affect cultivation success. Seven environmental factors were tested for their effects on growth of four geographically separated populations belonging to two species ofGracilaria. No specific or population differences were found under various temperature or salinity regimes. Specific differences occurred in responses to irradiance, daylength, sand burial and sand abrasion. Responses to epiphytes differed among both population and species. Epiphyte recruitment was inhibited by some populations and stimulated by others. Given the farming methods presently used in Chile, these results have ecological and economical importance, as they suggest that transplanting randomly from one to other type of habitat does not assure cultivation success.     

Effect of geographic background and equilibrium state on niche model transferability: predicting areas of invasion of Leptoglossus occidentalis

Niche conservatism providing support for using ecological niche modeling in biological invasions has been widely noticed, however, the equilibrium state and geographic background effect on niche model transferability has received scant attention. The western conifer seed bug, Leptoglossus occidentalis, native to western North America, has expanded its range eastward and has become an invasive pest in Europe and Asia. Niche models calibrated on the ranges of a small native population and two large expanding populations were compared. We found that the climate niche of L. occidentalis is conserved during its steady expansion in North America and rapid spread in Europe. Models based on the small western native range successfully captured the eastern expanding and introduced European populations, whereas the large area-based models varied with the presumed state of equilibrium. The equilibrium state based model succeeded but the non-equilibrium based model failed to predict the range in Europe. Our study estimates global invasion risk zones for L. occidentalis and suggests that, based on niche conservatism, modeling based on a reasonable geographic distribution at a climatic equilibrium of a species could guarantee the transferability of niche model prediction. Caution is warranted in interpreting low niche model transferability with niche differentiation and forwarding message for management strategy.     

Range-wide genetic differentiation of Eugenia dysenterica (Myrtaceae) populations in Brazilian Cerrado

The analysis of geographic patterns in genetic variation has been one of the most important current tools to understand ecological and evolutionary processes underlying population structure. However, inferring such processes from population data may be misleading if biased geographic samples are analyzed. Here we expand previous analyses of Eugenia dysenterica population structure in Brazilian Cerrado, analyzing a larger number of populations distributed throughout a broader geographic region covering most of species' range. We provide new estimates of genetic diversity and population structure based on SSR markers from both neutral and genic regions, using several cluster and ordination techniques. These analyzes reveal a continuous northwestern-southeastern gradient in population differentiation, and not two distinct clusters of populations as suggested in some previous studies. This more comprehensive analysis also reinforces that a simple process of stochastic differentiation do not explain the observed patterns. Moreover, we conclude that explanations for population differentiation may focus on why genetic diversity decreases toward southeastern populations and not necessarily on barriers and interruption of gene flow creating regional patterns of population differentiation.     

Resilience and Alternative Stable States of Tropical Forest Landscapes under Shifting Cultivation Regimes

Shifting cultivation is a traditional agricultural practice in most tropical regions of the world and has the potential to provide for human livelihoods while hosting substantial biodiversity. Little is known about the resilience of shifting cultivation to increasing agricultural demands on the landscape or to unexpected disturbances. To investigate these issues, we develop a simple social-ecological model and implement it with literature-derived ecological parameters for six shifting cultivation landscapes from three continents. Analyzing the model with the tools of dynamical systems analysis, we show that such landscapes exhibit two stable states, one characterized by high forest cover and agricultural productivity, and another with much lower values of these traits. For some combinations of agricultural pressure and ecological parameters both of these states can potentially exist, and the actual state of the forest depends critically on its historic state. In many cases, the landscapes’ ‘ecological resilience’, or amount of forest that could be destroyed without shifting out of the forested stability domain, declined substantially at lower levels of agricultural pressure than would lead to maximum productivity. A measure of ‘engineering resilience’, the recovery time from standardized disturbances, was independent of ecological resilience. These findings suggest that maximization of short-term agricultural output may have counterproductive impacts on the long-term productivity of shifting cultivation landscapes and the persistence of forested areas.     

<Emphasis Type="Italic">Ceratozamia zaragozae</Emphasis> Medellín-Leal (Zamiaceae), an endangered Mexican cycad: New information on population structure and spatial distribution

Ceratozamia zaragozae has been considered to be the most threatened cycad species in its genus since only 50 individuals were reported for the only known population in the state of San Luis Potosí, México. In this report we present information on newly discovered populations, as well as data on their population structure and spatial distribution. Six different populations were found, one of which is located in a Natural Protected Area. Population density was low (0.05 ± 0.038 ind/m²) and populations exhibited an unconventional ecological affinity for the genus, occurring on igneous soils in oak and pine-oak forests at elevations over 2000 m. Populations showed heterogeneous growth rates (λ = 0.89 ± 0.49). Spatial clustering patterns in all populations indicated adequate recruitment, low survival of juveniles, and spatial dependence between seedlings/juveniles and reproductive adults. We recommend the ex-situ cultivation of the species and the establishment of corridors between areas of habitat, in order to secure the preservation of the species.     

江苏省不同种植年限的西/甜瓜农田土壤线虫群落特征

在江苏省主要西/甜瓜产区,采集不同种植年限的西/甜瓜农田土壤,采用线虫形态学的鉴定方法,分析了不同种植年限西/甜瓜农田土壤线虫的数量、群落结构及相关生态指数的变化。结果表明:所有调查样点中,共发现土壤线虫54属,平均682条·100 g^-1干土,其中原杆属线虫、拟丽突属线虫和矮化属线虫在不同种植年限的西/甜瓜农田土壤中均为优势属;随着种植年限的增加,土壤线虫的总数量虽无显著变化,但其中食细菌类线虫和杂食-捕食类线虫数量显著减少,而植物寄生类线虫数量显著增加;植物寄生类线虫中的矮化属、根结属线虫数量不断增加;随着种植年限的增加,土壤线虫的多样性指数(H)、瓦斯乐斯卡指数(WI)、自由生活线虫成熟度指数(MI)显著降低,线虫通道指数(NCR)、植物寄生线虫成熟度指数(PPI)、PPI/MI显著升高,其他指数无显著变化;相关性分析结果显示,土壤线虫数量与土壤pH、速效磷、有效锌和有效硼均呈显著正相关;土壤p H、有机质、全氮、速效钾、有效硼和有效锌对土壤优势属线虫的影响较大;连续种植西/甜瓜会增加土壤植物寄生类线虫数量,进而可能造成西/甜瓜连作障碍的发生;连续种植6~10年,土壤线虫的多样性最低、稳定性最差,土壤环境已趋于恶化。     

In vivo survival of selected murine carrier red blood cells after separation by density gradients or aqueous polymer two-phase systems.

In order to explore possibilities of using erythrocytes as carrier systems for delivery of pharmacological agents, we have studied the in vivo survival of murine carrier red blood cell populations enriched in young or old cells. Hypotonic-isotonic dialysis has been used to modify the cells as carrier systems and Percoll/albumin density gradients or counter-current distribution in aqueous polymer two-phase systems to separate them according to age. Hypotonic-isotonic dialysis produces a decrease in the red blood cell populations in vivo survival rate (from 9.5 to 7.8 days). Among the cells modified as carriers, the enriched young red blood cell populations show a higher in vivo survival (half-life 6.5-7.4 days) than populations made up of predominantly old red blood cells (half-life 4.7-6.2 days). Half-life of young or old circulating red blood cells was approximately one day longer when these cells were separated by counter-current distribution rather than by Percoll density gradients. Based on these results, hypotonic-isotonic dialysis of whole and enriched young or old red blood cell populations, with higher or lower survival rates, can be considered as a useful tool for modification of these cells as carriers. The final outcome of such changes can be translated into better control of plasma drug delivery during therapy.     

Local adaptation in rotifer populations

The adaptation of organisms to their environment has been a subject of study for a long time. One method to study adaptations in populations involves comparing contemporary populations of the same species under different selective regimes, in what is known as a ??local adaptation?? study. A previous study of the cyclically parthenogenetic rotifer Brachionus plicatilis found high heritabilities for some life-history traits. Some of these life-history traits significantly differed among six populations from Eastern Spain and data suggested some traits to have higher evolutionary rates than neutral genetic markers. Here, by studying the same B. plicatilis populations, we examine the variation and possible local adaptation of their main life-history traits, closely related to fitness, in relation to habitat salinity and temperature. These environmental factors have been shown to play a key role in the ecological differentiation among co-generic species of B. plicatilis. The results obtained in this study show that: (1) the seasonality of rotifer populations from Eastern Spain has profoundly influenced sexual reproduction strategies; (2) salinity is probably a key factor in the ecological specialization of some populations; and (3) rotifer populations harbour high variability in their fitness components.     

Morphological and functional heterogeneity of Zajdela rat ascites hepatoma cells

This work studies the mechanisms of dysdifferentiation at cell neoplastic transformation based on the example of heterogeneity of the cell populations that form malignant tumors. Two natural fractions of Zajdela rat hepatoma cells are revealed that differ in the type of growth in the primary culture. Cells of one fraction are attached to substrate and are growing in monolayer (S-fraction), whereas cells of the other fraction are floating in the culture medium (F-fraction). Using the method of supravital observation of the primary culture cells (of 1–2 passages) at the limit of resolution of DIC microscopy, it has been established that both fractions contain cells of several types. Some of these cells are specific to one of the fractions and others are present in both fractions, but with different frequencies. Using the same method, it has been shown that, at the long-term separate cultivation of the fractions in vitro (more than 50 passages), both the cell composition and the initial ratio of cells of different types are changed in both of them. According to the data of flow DNA cytometry, cells of both fractions are hypotetraploid and have insignificant differences in the amount of DNA. After adaptation to conditions of cultivation in vitro, S-fraction cells have been found to have elevated proliferative activity compared to the cells of F-fractions; after long cultivation, the fractions already differ significantly (2.3 times) by this criterion. The content of the cell surface laminin, a marker of hepatocellular carcinomas, is higher on cells of the F-fraction than on those of the S-fraction. The interfraction differences are confirmed by immunologic estimations of the resistance of hepatoma cells to lyses of natural killer cells; cells of the S-fraction of the primary culture are 2.4 times more sensitive than cells of the F-fraction, while, after long-term cultivation, cells of the F-fraction become almost resistant to the cytotoxic action of natural killer cells. Based on the obtained data, the most probable pathways of the dysdifferentiation of rat hepatocytes upon the establishment of Zajdela hepatoma and at the long-term cultivation of cells of this tumor in vitro are discussed.     

Population genomics reveals evolution and variation of Saccharomyces cerevisiae in the human and insects gut

The quest to discover the variety of ecological niches inhabited by Saccharomyces cerevisiae has led to research in areas as diverse as wineries, oak trees and insect guts. The discovery of fungal communities in the human gastrointestinal tract suggested the host's gut as a potential reservoir for yeast adaptation. Here, we report the existence of yeast populations associated with the human gut (HG) that differ from those isolated from other human body sites. Phylogenetic analysis on 12 microsatellite loci and 1715 combined CDSs from whole-genome sequencing revealed three subclusters of HG strains with further evidence of clonal colonization within the host's gut. The presence of such subclusters was supported by other genomic features, such as copy number variation, absence/introgressions of CDSs and relative polymorphism frequency. Functional analysis of CDSs specific of the different subclusters suggested possible alterations in cell wall composition and sporulation features. The phenotypic analysis combined with immunological profiling of these strains further showed that sporulation was related with strain-specific genomic characteristics in the immune recognition pattern. We conclude that both genetic and environmental factors involved in cell wall remodelling and sporulation are the main drivers of adaptation in S. cerevisiae populations in the human gut.     

Landscape genetic structure of natural populations of Acacia caven in Argentina

Acacia caven is a South American species which shows remarkable climate tolerance and ecological adaptability; as such, this species is suitable for colonizing anthropogenically degraded sites. This species is widely distributed, and six varieties have been described based on both morphological traits and molecular markers. Moreover, Aronson (1992) suggests that, for this species, geographical separation could be associated with ecological differentiation. In this study, amplified fragment length polymorphisms were used to study genetic variation within and among 15 populations of A. caven from five eco-regions of Argentina and to investigate (1) whether the varieties are genetically coherent, (2) whether the varieties correspond consistently to a single eco-region, (3) the proportion of the species diversity explained within and among varieties and eco-regions. Eight of the 225 bands appear to be under positive selection. The remaining 217 neutral loci showed a high percentage of polymorphism (99.1%). The estimates of genetic diversity H _j were generally high. The F _ST (0.315) was highly significant, providing evidence for genetic structure among populations. Hierarchical analysis of molecular variance indicated that variation among eco-regions was 8.2% and highly significant. The higher component of variance was found within populations (67.5%). STRUCTURE analysis suggested that the optimal number of K?=?11. The results showed that, in most cases, geographic separation is associated with ecological differentiation. Since differentiation of A. caven populations studied here in eco-regions was highly significant, sampling should include a large number of trees within populations as well as covering the wide ecological diversity of the species.     

Nutrient-split feeding strategy for dialysis cultivation of Escherichia coli

Reduction in nutrient loss during dialysis cultivation of Escherichia coli on a glycerol medium was investigated. A dialysis reactor with an inner fermentation and an outer dialysis chamber was used. Aerobic condition was maintained by limiting the glycerol feed rate to an optimum value which was estimated from the oxygen requirements for glycerol oxidation and oxygen transfer capacity of the reactor. High reduction in nutrient loss was achieved by using water as the dialyzing fluid. However, osmotic movement of water from the dialysis to the fermentation chamber was observed, and the final cell concentration was low. With a nutrient-split feeding strategy (feeding glycerol directly to the fermentation chamber and dialyzing with salt solution), glycerol loss was small, there was no osmotic flux of water to the fermentation chamber, and the cell concentration was high. Both glycerol and salt loss could be avoided, and a cell concentration of 170 g/L was obtained when the dialysis process was substituted by addition of XAD adsorbents to the dialysis chamber. Application of this nutrient-split feeding strategy to cell cultivation in a stirred tank reactor, coupled with dialysis in external dialyzer modules, resulted in low cell concentrations. (c) 1993 Wiley & Sons, Inc.     

The widespread naturalisation of Nymphaea hybrids is masking the decline of wild-type Nymphaea alba in Hesse,Germany

The genus Nymphaea has long been cherished for its ornamental value. Since the end of the 19th century, intensive breeding has produced a large number of widely available hybrids used in horticulture. However, their escape from cultivation and their introduction into the wild pose problems for the conservation of Nymphaea alba in its natural distribution area because many white-flowered hybrids cannot be identified by morphological characters alone. To reliably identify plants of hybrid origin and to study the extent of the invasion of natural habitats by such hybrids, a case study was performed in which plant material was sampled at 34 locations in the federal state of Hesse, Germany, and neighbouring federal states. In addition to morphological information and historical data on the populations, an AFLP analysis was used to distinguish populations of true Nymphaea alba from those of hybrid origin.     

Dialysis cultivation of cyanobacteria

Various aspects and the significance of the dialysis cultivation method for physiology, ecology, and biotechnology are considered. In this method, the cell culture is separated by a semipermeable membrane with a medium volume that is greater by a factor of 5–10. Dialysis cultivation is a promising method for isolating symbiotic components, selecting bionts for mixed cultures, for exometabolite production, environmental monitoring, etc. Dialysis cultures are characterized by high rates of photosynthesis and growth and by a considerable increase in the duration of the stationary stage. The small volume of the dialysis bag contains high concentrations of physiologically active cells that can be used for the production of biomass and organic substances.     

Individual fates of mesenchymal stem cells <Emphasis Type="Italic">in vitro</Emphasis>

Background  

In vitro cultivated stem cell populations are in general heterogeneous with respect to their expression of differentiation markers. In hematopoietic progenitor populations, this heterogeneity has been shown to regenerate within days from isolated subpopulations defined by high or low marker expression. This kind of plasticity has been suggested to be a fundamental feature of mesenchymal stem cells (MSCs) as well. Here, we study MSC plasticity on the level of individual cells applying a multi-scale computer model that is based on the concept of noise-driven stem cell differentiation.     

Macrogeographical variability in the great call of Hylobates agilis: assessing the applicability of vocal analysis in studies of fine‐scale taxonomy of gibbons

Vocal characteristics have been used extensively to distinguish different taxonomic units of gibbons (family Hylobatidae). The agile gibbon (Hylobates agilis) has a disjunct distribution range in the Southeast Asian archipelago (remnants of the former Sunda landmass), and populations on different islands are currently recognized as distinct subspecies or even species. We recorded great calls from female agile gibbons from two populations on Sumatra and two populations on Borneo and examined the vocal variability on four levels: within‐individuals, between‐individuals, between‐populations and between‐islands. The primary objective was to evaluate the effect of geographical isolation on variability in song pattern and to test whether proposed island‐specific song characteristics exist, reflecting evolutionary divergence between Sumatran and Bornean agile gibbons. One hundred great calls were recorded from 20 females and analyzed for 18 spectral and temporal acoustic parameters. Principal component analysis followed by a nested ANOVA on components revealed a complex pattern of song variability not likely to reflect taxonomic or evolutionary relationship. We found no evidence that Sumatran and Bornean agile gibbons have evolved different vocal characteristics, refuting a distinction between them based on vocal characteristics. A high level of plasticity was found in great calls from the same individual, and generally the inferred pattern of variability suggested that ecological or social factors may confound any genetically based island dialects. Am. J. Primatol. 72:142–151, 2010. © 2009 Wiley‐Liss, Inc.     

Distribution of variation over populations

Understanding the significance of the distribution of genetic or phenotypic variation over populations is one of the central concerns of population genetic and ecological research. The import of the research decisively depends on the measures that are applied to assess the amount of variation residing within and between populations. Common approaches can be classified under two perspectives: differentiation and apportionment. While the former focuses on differences (distances) in trait distribution between populations, the latter considers the division of the overall trait variation among populations. Particularly when multiple populations are studied, the apportionment perspective is usually given preference (via F _ST/G _ST indices), even though the other perspective is also relevant. The differences between the two perspectives as well as their joint conceptual basis can be exposed by referring them to the association between trait states and population affiliations. It is demonstrated that the two directions, association of population affiliation with trait state and of trait state with population affiliation, reflect the differentiation and the apportionment perspective, respectively. When combining both perspectives and applying the suggested measure of association, new and efficient methods of analysis result, as is outlined for population genetic processes. In conclusion, the association approach to an analysis of the distribution of trait variation over populations resolves problems that are frequently encountered with the apportionment perspective and its commonly applied measures in both population genetics and ecology, suggesting new and more comprehensive methods of analysis that include patterns of differentiation and apportionment.     

The Cry1Ab Protein Has Minor Effects on the Arbuscular Mycorrhizal Fungal Communities after Five Seasons of Continuous Bt Maize Cultivation

The cultivation of genetically modified plants (GMP) has raised concerns regarding the plants’ ecological safety. A greenhouse experiment was conducted to assess the impact of five seasons of continuous Bt (Bacillus thuringiensis) maize cultivation on the colonisation and community structure of the non-target organisms arbuscular mycorrhizal fungi (AMF) in the maize roots, bulk soils and rhizospheric soils using the terminal restriction fragment length polymorphism (T-RFLP) analysis of the 28S ribosomal DNA and sequencing methods. AMF colonisation was significantly higher in the two Bt maize lines that express Cry1Ab, 5422Bt1 (event Bt11) and 5422CBCL (MON810) than in the non-Bt isoline 5422. No significant differences were observed in the diversity of the AMF community between the roots, bulk soils and rhizospheric soils of the Bt and non-Bt maize cultivars. The AMF genus Glomus was dominant in most of the samples, as detected by DNA sequencing. A clustering analysis based on the DNA sequence data suggested that the sample types (i.e., the samples from the roots, bulk soils or rhizospheric soils) might have greater influence on the AMF community phylotypes than the maize cultivars. This study indicated that the Cry1Ab protein has minor effects on the AMF communities after five seasons of continuous Bt maize cultivation.