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At least 19 recordsLinked to original sources
PubMed2026

Quantifying niche overlap and transgression in allopolyploid hybrids: Case study of Sorbus subgenus Aria.

BACKGROUND AND AIMS: Apomixis, the formation of seeds without recombination, facilitates adaptation and persistence under environmental change. By preserving hybrid genotypes over long time periods, apomixis may conserve adaptive trait combinations from parental niche margins. We tested whether apomictic entities occupy intermediate, marginal, or transgressive niche space relative to their parents and whether differentiation is associated with ploidy. METHODS: We studied polyploid Sorbus subgenus Aria in the Franconian Jura (Germany), comprising two progenitors Sorbus aria and S. collina, seven triploid entities, and a pool of genetically heterogenous individuals (single genotypes). Genetic structure was assessed using MIG-seq. Overall niche differentiation between parental taxa and hybrids was evaluated using Sørensen similarity of two-dimensional hypervolumes derived from principal component analysis (PCA) axes. Niche shifts were further analyzed using hypervolumes based on the three strongest PCA variables. Across 762 occurrences, observations ranged from 11 to 453 individuals per entity. KEY RESULTS: Environmental niche space was transgressive in three, significantly allocated towards the margins of parental niche space in one, while remaining intermediate in the other entities. Niche transgression occurred towards milder temperatures and drier conditions. Genetic analyses confirmed morphologically defined entities, although one morphotype was polyphyletic. Tetraploid S. collina significantly occupied warmer and wetter environments compared to other cytotypes. Triploids differed from S. aria along microtopographic gradients represented by the second PCA axis. CONCLUSIONS: Apomictic Sorbus entities show diverse strategies in niche occupation and can occupy environmental niche space at and beyond the limits of their parental taxa. Apomicts may conserve evolutionary adaptations at the edges of parental niche space that may otherwise be lost from, or fail to emerge in, the parental gene pool. Over long timescales these trait combinations may re-enter the parental gene pool through introgression, thereby reintroducing adaptations critical for survival under changing conditions.

Aria↗
PubMed2026

Restoration contexts shape the bacterial and fungal soil communities in desertification hotspots in the Brazilian semiarid region.

Desertification in the Brazilian semiarid has compromised ecosystem functionality, impacting soil microbial biodiversity. Thus, restoration strategies have been implemented, aiming to mitigate the negative impacts. However, little is known about their effects on soil microbial communities. In this study, we hypothesized that the two restoration contexts would promote distinct trajectories of soil microbial community recovery. We evaluated 36 soil samples collected from two desertification hotspots in the Brazilian semiarid, representing active (Gilbués) and passive (Irauçuba) restoration contexts. Soil DNA was extracted and subjected to 16S and ITS amplicon sequencing to characterize bacterial and fungal communities, respectively. Community differences were assessed using alpha-diversity metrics, redundancy analysis (RDA), and PERMANOVA. The results showed that within Gilbués (active restoration), bacterial and fungal community composition differed among soils under desertification and restoration. In Irauçuba (passive restoration), only native soils differed from both soils under desertification and restoration. Proteobacteria, Actinobacteriota, and Firmicutes (bacteria), and Ascomycota and Basidiomycota (fungi), were the dominant phyla in both hotspots. Bacterial and fungal communities showed distinct taxonomic patterns among native, degraded, and restored soils within each restoration context. Niche occupancy patterns also differed between restoration contexts. In conclusion, the two hotspots followed contrasting microbial recovery trajectories, demonstrating that restoration responses are context-dependent and vary according to the microbial groups, rather than supporting the universal superiority of one restoration strategy over the other.

Soil Microbiology↗
PubMed1992

The therapist as muse: greater roles for clinicians in fostering innovation.

Recent research on psychological and social factors that facilitate creativity indicates that clinicians can play important roles in fostering innovations crucial for national economic and social well-being. New research evidence indicates that individuals who carry increased liability for certain psychiatric illnesses, such as bipolar disorder (and possibly other disorders such as schizophrenia, as well) may tend to have unusual potential for creative accomplishment--particularly if they do not themselves have severe symptoms. Clinicians' professional skills give them special opportunities to nurture unusual creative potential in such individuals by using various approaches, ranging from more sensitive use of medication to creating special occupational niches in which unusually talented but psychologically vulnerable individuals can flourish. Clinicians are also needed to catalyze interdisciplinary reforms of occupational and educational institutions to remove authoritarian and harshly competitive conditions that discourage creativity and replace them with new social settings that actively foster innovation. Therapists, therefore, have important cultural roles to play in fostering creativity, not only through traditional professional roles, such as treating patients referred to them, but also through more "practice" ones, such as matching individuals with creative temperaments to optimal social settings, or inventing new social organizations. To fill these roles properly, therapists will themselves have to become more innovative in recasting their own professional identifies and responsibilities.

Creativity↗
PubMed2026

Rgg144/SHP144-controlled streptolancidin D mediates intra-species competition in Streptococcus pneumoniae with cumulative effect from other bacteriocins and fratricide.

UNLABELLED: Streptococcus pneumoniae is a major colonizer of the human nasopharynx, where inter- and intra-strain competition plays a critical role in shaping population structure and influencing vaccine outcomes. Bacteriocins are key mediators of intra-species competition, yet many of their functions and regulatory mechanisms remain poorly understood. Here, we identify and characterize streptolancidin D, a previously uncharacterized bacteriocin encoded by the sldA-T locus, and demonstrate its contribution to pneumococcal competition. Using isogenic streptolancidin-producing and non-producing variants of a naturally colonizing strain, we show that sldA-T contributes to the inhibition of competitor strains in in vitro biofilms and during murine co-colonization. Importantly, streptolancidin D also inhibited in vitro a subset of genetically diverse pneumococcal isolates representing multiple serotypes, whereas non-producing variants showed no activity. This indicates that its effect is broad and not restricted to isogenic interactions. Genomic analysis of over 7,500 pneumococcal genomes revealed that sldA-T is present in ~12% of isolates, with lineage-associated distribution patterns, and is consistently encoded downstream of the Rgg144/SHP144 quorum sensing system. We further demonstrate that sldA-T is regulated by this system, with sldA-T promoter activity abolished in a SHP-deficient background and partially restored by exogenous peptide stimulation. Finally, we show that streptolancidin D acts in concert with other bacteriocin systems and competence-mediated fratricide, highlighting a multifactorial antimicrobial strategy that enhances pneumococcal competitiveness. Overall, our findings identify a quorum sensing-regulated bacteriocin that contributes to pneumococcal competition and helps shape population dynamics. IMPORTANCE: Bacteriocins are central to bacterial competition and niche occupation, particularly in structured environments like the human nasopharynx. While several pneumococcal bacteriocins have been characterized, the functions of many remain unknown, limiting our understanding of how these systems shape strain fitness and population dynamics. We characterize streptolancidin D, a bacteriocin that enhances intraspecies competitiveness in vitro and in vivo and contributes to the inhibition of genetically diverse pneumococcal strains. We demonstrate that its expression is tightly regulated by the conserved Rgg144/SHP144 quorum sensing system and that the locus is distributed and shows synteny across multiple pneumococcal lineages. Our findings reveal that streptolancidin D operates within a broader network of bacteriocins and competence-associated mechanisms that collectively shape competitive interactions. By integrating genomic, functional, and regulatory analyses, this work expands the known repertoire of pneumococcal antimicrobial systems and provides new insights into the mechanisms underpinning competition and population structure in S. pneumoniae.

Bacteriocins↗
PubMed1998

Manipulating ruminal fermentation: a microbial ecological perspective.

The essential role of ruminal microflora in ruminant nutrition provides the potential for improvement in animal production via altering the numbers or activities of specific classes of microorganisms. Successful alterations will be facilitated by an understanding of the microbial ecology of the rumen based on its mechanistic underpinnings. Demonstrated improvements in ruminal fermentation can be traced to their consonance with well-established principles of microbial ecology (niche occupancy, selective pressure, adaptation, and interactions) and the thermodynamics and kinetics of substrate utilization. Application of these principles to several proposed alterations of the ruminal bacterial population allows a prediction of their relative feasibility. Improving fiber digestion, decreasing protein degradation, and detoxifying feed components that are present in low concentrations will be difficult to achieve in the rumen and are best approached by altering the feed, either genetically or with postharvest treatment. By contrast, the detoxification of feed components present in high concentration, and redirection of electron disposal away from methanogenesis, are more productive targets for microbiological research.

Animals↗
PubMed1999

The evolution of viruses, the emergence of viral diseases: a synthesis that Martinus Beijerinck might enjoy.

The relentless production of viral variants and their selection for improved "fit" are seen from the perspective of the infectious disease sciences as ever-changing viral phenotypes and emerging disease risks. In the Darwinian cause:effect equation, we can characterize very well the effects of mutation and selection--these are catalogued as new viral phenotypes or pathotypes. However, the selective forces themselves driving such changes remain rather mysterious. Many selective forces must be at work, acting on the virus, the host, the host population and the environment. In some instances the virus seems to test new unoccupied niches in the absence of any apparent environmental change, but usually it is clear that changes are driven by human activity. Most important must be the ever increasing density of human, domestic animal and crop plant populations and the consequent increased opportunities for transmission of viral variants. Also important must be the great changes affecting all ecosystems--these especially favor the emergence of new zoonotic viruses and viral "species jumpers." The great increase in human travel and transport carries exotic viruses, vectors and hosts around the world, again favoring viral occupation of new niches. The rise of bioterrorism adds yet another threat. Increasing numbers of emerging viral disease episodes seem to be linked to a decline in global resources for proven public health programs, agricultural extension programs, and the like, programs that have stood in the way of the spread and evolution of viral pathogens. If the relationship between viral evolution and the emergence of new viral diseases is rooted firstly in the host and the host population, then more research and resources must be directed to intervention at these levels rather than at the level of the viruses themselves.

Animals↗
PubMed1970

Contemporaneous disequilibrium, a new hypothesis to explain the "paradox of the plankton".

The diversity of lake phytoplankton is unexpectedly high, since the epilimnion of a lake is continuously mixing and might be expected to have only one or at most a few niches for primary producers. However, a carefully replicated series of samples from Castle Lake, Calif., showed a high degree of patchiness for many phytoplankton species, indicating that the rate of mixing is slow enough relative to the reproductive rate of the algae for many different niches to exist simultaneously. Productivity per unit biomass ratios, measured at Lake Tahoe, California-Nevada, shows that the turnover times for carbon in even this ultraoligotrophic lake are often less than 1 day. High diversity is associated with high productivity per unit biomass and high zooplankton populations in this lake.A contemporaneous disequilibrium model to explain the diversity of the lake phytoplankton is therefore highly plausible. At any one time, many patches of water exist in which one species is at a competitive advantage relative to the others. These water masses are stable enough to permit a considerable degree of patchiness to occur in phytoplankton, but are obliterated frequently enough to prevent the exclusive occupation of each niche by a single species.

California↗
PubMed1997

Density effects in population growth: an exploration.

In this paper a heuristic approach is taken to the investigation of density effects in population growth when the limiting factor is food resources. Explicit modeling of resource dynamics lets us to distinguish between density effects that are due to the diminution of the available resources, from density effects arising from direct interference among individuals. While species specific growth dynamics should vary extensively, it is possible to postulate some properties of hopefully, general applicability. This work examines the consequences of three postulates: (a) no growth occurs in the absence of resources; (b) the per capita growth rate increases with available resources; and (c) intraspecies interference competition causes the per capita growth rate to decrease as population density increases. Using these three postulates, I have constructed generalized functional description for each type of density dependence. These functions let us examine interspecies competition in class specific terms. The results indicate that intraspecies interference confers significant advantages in interspecies competition for long term occupation of ecological niches.

Animals↗
PubMed1993

Iron uptake mechanisms of pathogenic bacteria.

Most of the iron in a mammalian body is complexed with various proteins. Moreover, in response to infection, iron availability is reduced in both extracellular and intracellular compartments. Bacteria need iron for growth and successful bacterial pathogens have therefore evolved to compete successfully for iron in the highly iron-stressed environment of the host's tissues and body fluids. Several strategies have been identified among pathogenic bacteria, including reduction of ferric to ferrous iron, occupation of intracellular niches, utilisation of host iron compounds, and production of siderophores. While direct evidence that high affinity mechanisms for iron acquisition function as bacterial virulence determinants has been provided in only a small number of cases, it is likely that many if not all such systems play a central role in the pathogenesis of infection.

Animals↗
PubMed1990

Implications of aquatic animal health for human health.

Human health and aquatic animal health are organically related at three distinct interfaces. Aquatic animals serve as important contributors to the nutritional protein, lipid, and vitamin requirements of humans; as carriers and transmitters of many infectious and parasitic diseases to which humans are susceptible; and as indicators of toxic and carcinogenic substances that they can convey, in some part, from aquatic environments to man and other terrestrial animals. Transcending these relationships, but less visible and definable to many, is the role that aquatic animals play in the sustenance of our integrated planetary ecosystem. Up to the present, this ecosystem has been compatible with mankind's occupation of a niche within it at high but ultimately limited population levels. In the past century we have become clearly aware that human activities, particularly over-harvesting of aquatic animals together with chemical degradation of their habitats, can quite rapidly lead to perturbances that drastically shift aquatic ecosystems toward conditions of low productivity and impaired function as one of earth's vital organs. The negative values of aquatic animals as disease vectors are far outweighed by their positive values as nutritional sources and as sustainers of a relatively stable equilibrium in the global ecosystem. In the immediate future we can expect to see increased and improved monitoring of aquatic habitats to determine the extent to which aquatic animals cycle anthropogenic toxic and carcinogenic chemicals back to human consumers. In the long term, methods are particularly needed to assess the effects of these pollutants on reproductive success in aquatic communities and in human communities as well. As inputs of habitat-degrading substances change in quality and quantity, it becomes increasingly urgent to evaluate the consequences in advance, not in retrospect. A new, more realistic and comprehensive philosophy regarding aquatic environmental preservation and equally new and comprehensive technological advances reflective of this philosophy will be required. In the next century we will see a serious test of whether or not mankind has lost its ability to foresee and forestall the side effects of scientific and technological ingenuity.

Animals↗
PubMed1981

The reduction of occupational stress among elderly lawyers: the creation of a functional niche.

The question of how older lawyers function in the context of what is generally a high stress occupation is examined from data drawn from a random stratified sample of 130 members of the legal profession. It is shown that elderly lawyers are able to reduce work stress (largely deriving from volume, responsibility, clients, and trials) by control over the quantity and focus of their work, as well as through client selection. Elderly lawyers are able to create a relatively stress free work role, which is in fact a functional niche for them within the profession. The result is high job satisfaction and low rates of retirement among elderly practitioners. Two factors: work role compensation and work role autonomy, are isolated from the legal data and proposed as important variables in a general theory of retirement behavior.

Adaptation, Psychological↗
PubMed1970

Ecological consequences of island colonization by southwest Pacific birds. II. The effect of species diversity on total population density.

Among southwest Pacific birds colonizing a species-poor island from a species-rich island, spatial expansion of the niche to include a wider range of altitudes, habitats, or vertical strata is often an immediate response, while changes in foraging techniques and diet usually occur more slowly and require genotypic change. Despite occupation of spatially broader niches by some colonizing species and increases in abundance by others, the total population density of the whole avifauna is up to nine times lower on a species-poor island than in a comparable habitat on a species-rich island. Total population density varies among islands approximately linearly with the number of species in the lowlands, supralinearly at higher elevations. Part of the explanation is that many birds on small islands expand into niche space which is suboptimal for them and from which they would be excluded by species utilizing this niche space optimally on a species-rich island. The other suggested explanation is an intrinsic inefficiency or loss of fitness among populations on small Pacific islands compared to large-island populations, due to impoverished gene pools, reduced selection pressure, and low degree of endemism.

Animals↗
PubMed1991

Comparative aspects of diet in Amazonian forest-dwellers.

Recent research shows that lowland forests of the Amazon Basin differ in numerous ways including features of climate and soils, faunal composition and forest structure, composition and phenology. Such differences strongly suggest that single-factor models used to explain features of human ecology in Amazonia may be too limited. A comparative study of the dietary ecology of four forest-living indigenous groups in Brazil (Arara, Parakana, Arawete, Mayoruna) revealed a number of differences. Primary crops, as well as animal types most utilized as prey, were found to differ markedly between groups. Although some differences can be accounted for by general environmental factors, no compelling single environmental factor can explain why any one group could not behave dietarily in ways more similar to another. Many of these intergroup dietary differences appear to represent a type of cultural character displacement that aids in distinguishing the members of one group from another. As all human groups, through the medium of culture, are actual or potential occupants of the same dietary niche, each group may distance itself from potential dietary rivals through cultural conventions. This behaviour may be justified, as the lack of overlap between forest-living groups in combination with generally intense intergroup hostility suggests that the biomass and distribution patterns of critical dietary resources in this environment may set limits to viable population size for particular areas.

Animals↗
PubMed1997

An occupational tale of two cities: minorities in London and New York.

In this paper, queuing theory is tested through an examination of the occupational attainment of six groups of non-whites in London and New York. Workers in the dominant economy are distinguished from those in the niche economy and emphasis is placed on the former. Black male immigrants in New York and black female immigrants in London hold more favorable occupational status. These results reflect differences in (1) the presence of indigenous minorities--African Americans and Puerto Ricans--in New York but not London, and (2) the relatively low position of indigenous minority males compared to the relatively middling position of indigenous minority females in New York's labor queue.

Adult↗
PubMed1999

Resource partition history and evolutionary specialization of subunits in complex systems.

Specialization for part of the resources available is a common adaptation leading to diversification in biological systems. In complex ecological communities, the history of diversification of parts of a system correlates with the structure of the system in present times. Abundances and sequences of resource partition of species expected by a sequential broken stick model are compared with observed abundances of species and their sequences of evolutionary divergence. Where resources are abundant, first resource partitions correspond to most ancient speciations, and last to recent speciations. The inverse is true when resources are scarce, agreeing with the occupation of extreme habitats by recent species. Diverging species seem to specialize by dividing the niche of common ancestors. Similar trends exist inside genera as well as between families, suggesting similar patterns in diversification and specialization at other levels of biological organization, such as evolution of functional complexes of macromolecules and organs embryogenesis.

Animals↗