Cyanobacterial dominance in lakes

Cyanobacterial dominance in lakes has received much attention in the past because of frequent bloom formation in lakes of higher trophic levels. In this paper, underlying mechanisms of cyanobacterial dominance are analyzed and discussed using both original and literature data from various shallow mixed and deep stratifying lakes from temperate and (sub)tropical regions. Examples include all four ecotypes of cyanobacteria sensu Mur et al. (1993), because their behavior in the water column is entirely different. Colony forming species (Microcystis) are exemplified from the large shallow Tai Hu, China. Data from a shallow urban lake, Alte Donau in Austria are used to characterize well mixed species (Cylindrospermopsis), while stratifying species (Planktothrix) are analyzed from the deep alpine lake Mondsee. Nitrogen fixing species (Aphanizomenon) are typified from a shallow river-run lake in Germany. Factors causing the dominance of one or the other group are often difficult to reveal because several interacting factors are usually involved which are not necessarily the same in different environments. Strategies for restoration, therefore, depend on both the cyanobacterial species involved and the specific causing situation. Some uncertainty about the success of correctives, however, will remain due to the stochastic nature of the events and pathways leading to cyanobacterial blooms. Truly integrated research programs are required to generate predictive models capable of quantifying key variables at appropriate spatial and temporal scales.     

Tree dominance and diversity in Minas Gerais,Brazil

Quantifying diversity is an old challenge for ecologists and is also a social demand given the increasing threats to natural areas. We sought to work on these issues by using data from 158 vegetation remnants (over 350,000 trees) in southeastern Brazil (Minas Gerais State—MG, nearly 600,000 km²). Specifically, we sought to answer the following questions. (1) How many trees and tree species currently exist in MG vegetation remnants? (2) How much of such biodiversity is present in each vegetation domain (Atlantic Forest, Cerrado and Caatinga) and vegetation type (Seasonally Dry tropical forest “semideciduous”, Seasonally Dry tropical forest “deciduous”, Rain Forest, Swamp, Cerrado and Cerradão) in MG? (3) How much has been lost in regards to tree amount and tree species? We built a 0.1-degree cell grid to estimate the number of trees via spatial regression and used Fisher’s alpha and Fisher’s log series to provide estimates on how many tree species there are and were in MG. We found the number of trees in Minas Gerais to be approximately 24.5 × 10⁹, and the number of tree species to be between 3592 and 3743. The most abundant species distribution among the vegetation domains and vegetation types followed inversely the environmental heterogeneity of the classes. Consequently, the most abundant species in MG belonged to the Cerrado domain, where there was less environmental heterogeneity. The numbers of trees and tree species lost were estimated at 68.54 and 4.03–8.42% of the original values, respectively. We discuss that due to the consequences of human impacts that go back in the region for over a thousand years, other processes not considered in this study, such as habitat degradation by isolation, alterations of food webs, unsustainable use, and climate change, might have caused local extinctions and potentially increased the number of species lost. We believe our results may guide conservation initiatives by providing a base for future environmental laws, parks planning, and the development of more appropriate vegetation management techniques in MG. In addition, our results may inspire future quantitative ecological studies in the tropics.     

Allogrooming in cattle: Relationships between social preferences,feeding displacements and social dominance

The aim of this study was to describe the allogrooming behaviour of group-housed lactating cows (Bos taurus) as it relates to social dominance, friendship, parity and level of feeding competition. We measured the socio-negative (displacements at the feeder and in the lying stalls) and socio-positive interactions (allogrooming and preferential spatial associations) in six groups of eight dairy cows. This experimental model has been shown to be useful in investigating the effects of high social pressure in groups of cattle. The level of social competition was manipulated by halving the access to the feeder. Allogrooming was observed mostly at the feeder after fresh feed delivery and during the night between 12 and 2 a.m. Dominance rank had no effect on the expression of allogrooming. When competition between animals increased, allogrooming declined, especially in low-ranking, primiparous animals. In addition to its role in coat hygiene and potential role in reducing tension between animals competing for feed, we conclude that allogrooming may be a behaviour reflecting friendship in cows, because it is correlated to preferential associations between partners at the feeder. We suggest that primiparous cows are more susceptible to suffer from a lack of hygiene or socio-positive relationships when submitted to high competitive pressure, especially when they are mixed with more experienced animals that could have better coping strategies in a high competition situation.     

Floristic composition, environmental variation and species distribution patterns in burned grassland in southern Brazil.

In regularly burned grassland on Morro Santana, Porto Alegre, RS, Brazil, we investigated differences in the floristic composition and their relation to soil properties, aspect and distance from the forest border. In 48 plots of 0.75 m2, we identified a total of 201 species from a local species pool of approximately 450 to 500 species. Most species occurred in low frequencies, showing clumpy distribution patterns in the studied area. Multivariate analysis showed that plots close to the forest edge clearly differed from plots in the open grassland concerning composition and structure. Plots exposed to the north differed from plots on the top of the hill both in the composition of species as well as in soil variables, mainly due to shallower soil in the former. No strong relation between soil properties and variation in vegetation composition could be detected at a finer scale. The studied grassland, as all grassland vegetation in southern Brazil, is very rich in species compared to other grassland formations worldwide. However, this high biodiversity and conservational value of Campos vegetation in general has so far not been recognized properly. Disturbance is essential to maintain this open vegetation type and its species richness. Fire should be considered as a management option in the absence of grazing.     

Cyanobacterial two-component proteins: structure, diversity, distribution, and evolution.

A survey of the already characterized and potential two-component protein sequences that exist in the nine complete and seven partially annotated cyanobacterial genome sequences available (as of May 2005) showed that the cyanobacteria possess a much larger repertoire of such proteins than most other bacteria. By analysis of the domain structure of the 1,171 potential histidine kinases, response regulators, and hybrid kinases, many various arrangements of about thirty different modules could be distinguished. The number of two-component proteins is related in part to genome size but also to the variety of physiological properties and ecophysiologies of the different strains. Groups of orthologues were defined, only a few of which have representatives with known physiological functions. Based on comparisons with the proposed phylogenetic relationships between the strains, the orthology groups show that (i) a few genes, some of them clustered on the genome, have been conserved by all species, suggesting their very ancient origin and an essential role for the corresponding proteins, and (ii) duplications, fusions, gene losses, insertions, and deletions, as well as domain shuffling, occurred during evolution, leading to the extant repertoire. These mechanisms are put in perspective with the different genetic properties that cyanobacteria have to achieve genome plasticity. This review is designed to serve as a basis for orienting further research aimed at defining the most ancient regulatory mechanisms and understanding how evolution worked to select and keep the most appropriate systems for cyanobacteria to develop in the quite different environments that they have successfully colonized.     

Cyanobacterial ecology across environmental gradients and spatial scales in China's hot and cold deserts

Lithic photoautotrophic communities function as principal primary producers in the world's driest deserts, yet many aspects of their ecology remain unknown. This is particularly true for Asia, where some of the Earth's oldest and driest deserts occur. Using methods derived from plant landscape ecology, we measured the abundance and spatial distribution of cyanobacterial colonization on quartz stony pavement across environmental gradients of rainfall and temperature in the isolated Taklimakan and Qaidam Basin deserts of western China. Colonization within available habitat ranged from 0.37+/-0.16% to 12.6+/-1.8%, with cold dry desert sites exhibiting the lowest abundance. Variation between sites was most strongly correlated with moisture-related variables and was independent of substrate availability. Cyanobacterial communities were spatially aggregated at multiple scales in patterns distinct from the underlying rock pattern. Site-level differences in cyanobacterial spatial pattern (e.g. mean inter-patch distance) were linked with rainfall, whereas patchiness within sites was correlated with local geology (greater colonization frequency of large rocks) and biology (dispersal during rainfall). We suggest that cyanobacterial patchiness may also in part be self-organized - that is, an outcome of soil water-biological feedbacks. We propose that landscape ecology concepts and models linking desert vegetation, biological feedbacks and ecohydrological processes are applicable to microbial communities.     

Spatial distribution of functional traits of bryophytes along environmental gradients in an Atlantic Forest remnant in north-eastern Brazil

ABSTRACT

Background: Functional trait-based approaches have been used to identify patterns of plant species diversity and composition related to environmental variability/changes. Bryophytes are rapidly affected by perturbations and thus their traits and distribution are expected to show well-defined relationships with environmental variability.

Aim: To quantify the impacts of fragmentation on the diversity and structure of epiphytic bryophytes to vertical and horizontal environmental gradients in an Atlantic Forest remnant.

Methods: Six functional traits related to water relations and light tolerance were recorded and one of them, the leaf lobule area in liverworts, was selected for morphometric measurements along the gradients analysed. Functional diversity and composition metrics of bryophytes along gradients were compared.

Results: Functional diversity changed little along the vertical and horizontal gradients. Conversely, the functional composition of traits changed markedly. Traits related to water storage, such as the presence and area of lobules, and to protection against excess light incidence, such as dark pigments, were more numerous in the canopy and at the fragment edge.

Conclusions: Functional composition is more correlated with the vertical and horizontal gradients than functional diversity. The lobule of liverworts stood out as the most relevant trait to explain the adaptive strategies of bryophytes.     

Host preferences of the phlebotomine sandfly Lutzomyia longipalpis in Amazonian Brazil

Experiments were undertaken to determine the relative attractiveness of humans, dogs and chickens to Lutzomyia longipalpis, the principal vector of Leishmania chagasi causing American visceral leishmaniasis. Field experiments in two villages on Marajó Island, Pará State, Brazil, showed that one boy attracted significantly more flies than one dog or chicken, and slightly fewer flies than a group of six chickens. Experiments with laboratory-bred female flies showed that a significantly greater number of flies engorged on a single human than on either a single dog or chicken, and man-biting catches demonstrated the willingness of flies to bite in the field. It appears that Lu.longipalpis has catholic feeding habits, the attractiveness of different hosts being largely a function of their relative sizes. These results are discussed with reference to the epidemiology of visceral leishmaniasis in Brazil.     

Brazil cannot risk its environmental leadership

Brazil is an international environmental leader that has led important negotiations to set sustainable development targets over the last decade. However, in terms of national policies, Brazil is consistently making decisions that go against the global policies it ratifies. For instance, Brazilian governors have recently revised the Brazilian Forest Act ‐ its main environmental legislation on private land, reduced the area covered by some protected areas and allowed the creation of new hydropower plants on undisturbed Amazonian rivers, and have plans to open indigenous reserves to mining. Among other consequences, these controversial actions made by national leaders may increase CO₂ emissions and propel a massive loss of species, with irreversible consequences to the provision of ecosystem services and goods. In this paper, I present inconsistent actions made by policy and decision makers in Brazil and argue for a more focused environmental decision in Brazil, which matches the country's international position as a leader and that could help Brazil to achieve the status of a biodiversity superpower.     

The tick Ixodes ricinus: distribution and climate preferences in the western Palaearctic

In this study, multivariate spatial clustering on monthly normalized difference vegetation index (NDVI) maps is used to classify ecological regions over the western Palaearctic. This classification is then used to delineate the distribution and climate preferences of populations (clades) of the tick Ixodes ricinus L. (Acari: Ixodidae) from a geographically extensive dataset of tick records and a gridded 2.5-km resolution climate dataset. Using monthly layers of the NDVI, regions of similar ecological attributes were defined and nine populations with significant differences in critical climate parameters (P< 0.005) were detected. Grouping of tick records according to other categories, such as political divisions, a 4 degrees x 4 degrees grid overlying the study area, or the CORINE) and USGS) vegetation classification schemes did not provided significantly separated populations (P = 0.094-0.304). Factor analysis and hierarchical tree clustering provided an ecological overview of these tick clades: two Mediterranean and one Scandinavian (western) clades are clearly separated from a node that includes clades of different parts of central Europe and the British Isles, with contrasting affinities between the different clades. The capture records of these ecologically separated clades produce a clear bias when bioclimate envelope modelling is applied to the mapping of habitat suitability for the tick in the western Palaearctic. The best-performing methods (Cohen's kappa = 0.834-0.912) use partial models developed with data from each ecoregion, which are then overlapped over the region of study. It is concluded that the use of ecologically derived ecoregions is an objective step in assessing the presence of ecologically different clades, and provides a guide in the development of data partitioning for habitat suitability modelling.     

Do hens suffer in battery cages? environmental preferences and welfare

The question ‘Do hens suffer in battery cages?’ is difficult to answer because of the problem of objectively assessing suffering in animals. It is argued that preference tests may be one way of throwing light on this difficult problem. This paper describes some experiments on habitat preference in domestic hens. No preference was observed between a commercial battery cage and a large pen when hens were given continuous access to the two. A simultaneous choice between a battery cage and an outside hen-run showed a clear preference for the run, but choice was strongly influenced by prior experience. The strength of the run preference was investigated by ‘pitting’ the run against food and access to companions.     

Food distribution,dominance, and aggressive behaviors in bonnet macaques

Resource availability or distribution may affect interindividual competition in species such as primates, which forage in social groups, and several field studies suggest that dominance status predicts access to restricted food sources. Increased competition due to restricted resources may result in the intensification of aggressive behaviors. The study reported here examines the impact of manipulation of the distribution of food resources in a laboratory-housed group of bonnet macaques to assess the impact of distribution on aggressive behaviors. Food was restricted to a space which allowed access to only one or two individuals at a time or was dispersed throughout the living enclosure to allow universal access in alternating periods. During periods of clumped distribution, the monkeys obtained access to the food in order of their dominance status in the group. In addition, overall levels of aggressive behaviors increased, submissive behavior increased, and play decreased during periods of clumped distribution of food. These results confirm the findings from field studies indicating increases in agonism with restriction of food resources. These findings also have implications for primate colony management, in terms of developing strategies for minimizing intragroup aggression in captive groups.     

The distribution and habitat preferences of the zebrafish in Bangladesh

The present study presents the results of a survey of a wide range of water bodies in Bangladesh to identify and describe Danio rerio habitat preferences. Field-based experiments were conducted to determine the vertical distribution of D. rerio in the water column, together with five other fish species commonly found in association with D. rerio. Danio rerio is a floodplain rather than riverine species, being most abundant in shallow lakes, ponds and ditches, typically in open locations with relatively clear water and abundant vegetation at the margins. It is commonly found in water bodies with a connection to rice cultivation and is more common in the north of Bangladesh than the south. Danio rerio occupies the whole of the water column and is observed as frequently in open water as amongst aquatic vegetation.     

Visualising the environmental preferences of Pinus tecunumanii populations

A network of 92 pedigreed ex situ conservation plantings of Pinus tecunumanii, established as replicated progeny within provenance trials, is used to present a principal components-based analysis that illustrates the climatic preferences of 23 populations from the species’ native range. This meta-analysis quantifies changes in the relative productivity, assessed as individual-tree volume, of populations across climatic gradients and associates the preference of a population with increased volume production along the climatic gradient. Clustering and ordination on the matrix containing estimates of change in productivity for each population summarise differentials in productivity associated with climatic gradients. The preference of populations along principal components therefore reflects the adaptive profiles of populations, which may be used with breeding-value estimates from routine genetic evaluations to assist with the development of deployment populations targeting different environments. As well, the approach may be used to test whether the preference of a population, estimated as population loadings for growth differentials, is affected by the climate in the native range of the population. This relationship may be interpreted as an estimate of how much local climate shapes the adaptive profiles of populations. The amount and seasonality of precipitation most clearly differentiate the adaptive profiles of populations, with less variation in the population responses explained by temperature differentiation. As expected from type-B correlation estimates, most populations exhibited small changes in relative productivity across climatic gradients. However, patterns of similarities in adaptive profiles among populations were evident using spatial orientation to display population responses to the climatic variables experienced in the provenance trials. Clustering and ordination of population responses derived from empirical data served to identify populations that responded positively or negatively to climatic variables; this information may help guide conservation genetics efforts, direct the deployment of germplasm, or identify seed sources that are sensitive to changes in climatic variables. Linking response patterns to the climatic data from the native range of each population indicated little effect of local climate shaping adaptive profiles.     

Geographic distribution of HBsAg subtypes in Brazil

HBsAg positive serum samples (896) from five brazilian regions were analysed for HBsAg subtypes. The presence of five different subtypes (ayw2, ayw3, ayw4, adw2 and adw4) was detected. In Northern region subtypes adw4 (41.2%) and adw2 (37.2%) were predominant. In the North East only subtype adw2 was encountered. In Central West, South-East and South, subtypes ayw2, ayw3, adw2 and adw4 were present, with predominance of adw2 in Central West and South East (84.3% and 69.4% respectively) whereas in the South the predominant subtype was ayw3 (41.9%) followed by ayw2 (36.4%). Subtypes ayw1, ayr and adr were not found among the samples studied. These results show the difference in the incidence of HBsAg subtypes in the different regions of Brazil and their significance in relation to the colonization and migrations in this country.     

Four sites with contrasting environmental stress in southeastern Brazil: relations of species, life form diversity, and geographic distribution to ecophysiological parameters

Some ecophysiological parameters related to plant performance and fitness (carbon and nitrogen isotope composition and total C and N concentrations; in situ chlorophyll fluorescence measurements) were determined for over 30 species in four habitats bordering the montane Atlantic rain forest of Brazil, along a gradient of altitude and rainfall: a dry coastal forest, two areas of sandy coastal plain vegetation (restingas) , and a high altitude campo. There was a considerable diversity of ecophysiological behaviour within and between the functional groups we created based on plant life-forms. For instance, both crassulacean acid metabolism (CAM) and C₃ species were found in most life-forms sampled and throughout all habitats. Despite the variation in rainfall regimes, average overall water-use efficiency was similar between sites, particularly for C₃ species, while no clear pattern regarding nitrogen-use emerged in this respect. Acute and chronic photoinhibition were found in many species across this gradient, even in CAM plants. However, on average, chronic photoinhibition and lower energy dissipation capacity were more characteristic of plants from the restinga habitats. This suggests that, although plants colonizing these habitats have evolved features to deal with water shortage, adaptation to high light levels has not been fully achieved yet. The ecophysiological performance of some individual species in distinct habitats and in distinct microhabitats within habitats is also discussed.     

Intensification of cattle ranching production systems: socioeconomic and environmental synergies and risks in Brazil

Intensification of Brazilian cattle ranching systems has attracted both national and international attention due to its direct relation with Amazon deforestation on the one hand and increasing demand of the global population for meat on the other. Since Brazilian cattle ranching is predominantly pasture-based, we particularly focus on pasture management. We summarize the most recurrent opportunities and risks associated with pasture intensification that are brought up within scientific and political dialogues, and discuss them within the Brazilian context. We argue that sustainable intensification of pasturelands in Brazil is a viable way to increase agricultural output while simultaneously sparing land for nature. Since environmental degradation is often associated with low-yield extensive systems in Brazil, it is possible to obtain higher yields, while reversing degradation, by adopting practices like rotational grazing, incorporation of legumes and integrated crop-livestock-forestry systems. Technical assistance is however essential, particularly for small- and medium-scale farmers. Sound complementary policies and good governance must accompany these measures so that a ‘rebound effect’ does not lead to increased deforestation and other adverse social and environmental impacts. It is also important that animal welfare is not compromised. Although the discussion is presented with respect to Brazil, some aspects are relevant to other developing countries.     

Cyanobacterial metallothioneins: Biochemistry and molecular genetics

Summary Metallothioneins have been extensively studied in many different eukaryotes where they sequester, and hence detoxify, excess amounts of certain metal ions. However, the precise functions of many of these molecules are not fully understood. This article reviews literature concerning their namesakes in prokaryotes.Abbreviations MT metallothionein - MRE metal regulatory element     

Apical dominance and the effect of gravity on nutrient distribution

Summary The effect of orientation with resepct to gravity on the accumulation of phosphorus-32 into lateral and leader apices has been investigated in seedling trees of Betula pubescens. In upright, well-branched seedlings, showing only weak apical dominance, basally injected ³²P is distributed more or less equally among the lateral and leader apices. Re-orientation treatments which result in the assumption of strong dominance by a lateral apex also result in a marked accumulation of ³²P into that apex. This effect of orientation on nutrient transport is manifested within two to four days after application of the gravimorphic treatments.The results are discussed in the light of modern concepts of hormone-directed nutrient transport and a working hypothesis for the role of gravity in apical dominance of woody plants is suggested.