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Results for “Spatial niche”

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PubMed1998

Reproductive interference in concurrent infections of two Protopolystoma species (Monogenea: Polystomatidae).

The prevention of interspecific reproductive interference is one possible explanation for spatial niche divergence between congeneric monogeneans. However, there is little direct evidence that reproductive interactions with other species are potentially deleterious to the majority of parasitic platyhelminths. Xenopus fraseri-like clawed toads from lowland rainforest in eastern Democratic Republic of Congo are infected by two species of polystomatid monogenean, Protopolystoma fissilis and Protopolystoma ramulosus. Both occur as adults in the host urinary bladder, and exhibit identical copulatory structures and similar body sizes. The small area of the habitat in relation to parasite body size makes close proximity inevitable in concurrent infections. Eggs were collected from five naturally infected hosts: two of these harboured concurrent infections, and three were infected with P. fissilis only. Eggs from concurrent infections showed reduced viability (57.6% embryonation, n = 413) compared with those from P. fissilis-only infections (85.2%, n = 439). This effect may be due to some form of reproductive interference, possibly failure to develop following interspecific cross-fertilisation.

Animals↗

PubMed2000

Suitability of two root-mining weevils for the biological control of scentless chamomile, Tripleurospermum perforatum, with special regard to potential non-target effects.

The biology and host range of the two root-mining weevils Diplapion confluens Kirby and Coryssomerus capucinus (Beck), two potential agents for the biological control of scentless chamomile Tripleurospermum perforatum (Mérat) Laínz, were studied in the field in southern Germany and eastern Austria, and in a common garden and under laboratory conditions in Delémont, Switzerland from 1993 to 1999. Both weevils were univoltine, and females started to lay eggs in early spring. Diplapion confluens had three and C. capucinus five instars. Larvae of both species were found in the field from mid-April until the end of July; later instars preferentially fed in the vascular cylinder of the shoot base, root crown or root. Although larvae of both species occupy the same temporal and spatial niche within their host plants, they occurred at all investigated field sites together, and showed a similar distribution within sites. No negative or positive interspecific association was detected. Host-specificity tests including no-choice, single-choice, and multiple-choice tests under confined conditions, as well as tests under field conditions with natural and augmented insect densities revealed that both herbivores were specific to plant species in the tribe Anthemideae. However, their development to mature larva or adult on several cultivated plants, as well as on one plant species native to North America, rendered them unsuitable for field release in North America. It was concluded that to investigate non-target effects reliably, host-specificity tests with biological control agents should be carried out under a variety of conditions, particularly with augmented insect densities, as are expected to occur naturally after release.

Animals↗

PubMed2002

The role of parasites in sympatric and allopatric host diversification.

Exploiters (parasites and predators) are thought to play a significant role in diversification, and ultimately speciation, of their hosts or prey. Exploiters may drive sympatric (within-population) diversification if there are a variety of exploiter-resistance strategies or fitness costs associated with exploiter resistance. Exploiters may also drive allopatric (between-population) diversification by creating different selection pressures and increasing the rate of random divergence. We examined the effect of a virulent viral parasite (phage) on the diversification of the bacterium Pseudomonas fluorescens in spatially structured microcosms. Here we show that in the absence of phages, bacteria rapidly diversified into spatial niche specialists with similar patterns of diversity across replicate populations. In the presence of phages, sympatric diversity was greatly reduced, as a result of phage-imposed reductions in host density decreasing competition for resources. In contrast, allopatric diversity was greatly increased as a result of phage-imposed selection for resistance, which caused populations to follow divergent evolutionary trajectories. These results show that exploiters can drive diversification between populations, but may inhibit diversification within populations by opposing diversifying selection that arises from resource competition.

Animals↗

PubMed2002

Water deficits and hydraulic limits to leaf water supply.

Many aspects of plant water use -- particularly in response to soil drought -- may have as their basis the alteration of hydraulic conductance from soil to canopy. The regulation of plant water potential (Psi) by stomatal control and leaf area adjustment may be necessary to maximize water uptake on the one hand, while avoiding loss of hydraulic contact with the soil water on the other. Modelling the changes in hydraulic conductance with pressure gradients in the continuum allows the prediction of water use as a function of soil environment and plant architectural and xylem traits. Large differences in water use between species can be attributed in part to differences in their 'hydraulic equipment' that is presumably optimized for drawing water from a particular temporal and spatial niche in the soil environment. A number of studies have identified hydraulic limits as the cause of partial or complete foliar dieback in response to drought. The interactions between root:shoot ratio, rooting depth, xylem properties, and soil properties in influencing the limits to canopy water supply can be used to predict which combinations should optimize water use in a given circumstance. The hydraulic approach can improve our understanding of the coupling of canopy processes to soil environment, and the adaptive significance of stomatal behaviour.

Journal Article↗

PubMed2001

Lacustrine spatial distribution of landlocked Atlantic salmon populations assessed across generations by multilocus individual assignment and mixed-stock analyses.

The objective of this study was to assess the spatiotemporal distribution of four landlocked Atlantic salmon (Salmo salar) populations during their sympatric feeding phase in lake St-Jean (Québec, Canada). A total of 1100 fish captured over a period of 25 years was genotyped at six microsatellite loci in order to assess the temporal stability of the relative proportion of each population in different lake sectors using both individual-based assignment and mixed-stock analysis. Estimates of relative proportions obtained from both methods were highly correlated. A nonrandom spatial distribution of populations was observed for each period and, despite the fact that the overall proportion of each population varied over time, the pattern of differential distribution remained generally stable over time. Furthermore, there were indications that the extent of horizontal spatial overlap among populations was negatively correlated with that of their genetic differentiation at both microsatellites and a major histocompatibility complex locus, and independent of the geographical distance between the rivers of origin. We discuss the hypothesis that the temporal stability of spatial distribution, the lack of an association between spatial partitioning and geographical distance between rivers of origin, and the apparent negative correlation between spatial overlap and genetic differentiation, reflect the outcome of selective pressures driving behavioural differences for spatial niche partitioning among populations.

Animals↗

PubMed2002

Mechanisms linking diversity, productivity and invasibility in experimental bacterial communities.

Decreasing species diversity is thought to both reduce community productivity and increase invasibility to other species. However, it remains unclear whether identical mechanisms drive both diversity-productivity and diversity-invasibility relationships. We found a positive diversity-productivity relationship and negative diversity-invasibility and productivity-invasibility relationships using microcosm communities constructed from spatial niche specialist genotypes of the bacterium Pseudomonas fluorescens. The primary mechanism driving these relationships was a dominance (or selection) effect: more diverse communities were more likely to contain the most productive and least invasible type. Statistical elimination of the dominance effect greatly weakened the diversity-invasibility relationship and eliminated the diversity-productivity relationship, but also revealed the operation of additional mechanisms (niche complementarity, positive and negative interactions) for particular combinations of niche specialists. However, these mechanisms differed for invasibility and productivity responses, resulting in the invasibility-productivity relationship changing from strongly negative to weakly positive. In the absence of the dominance effect, which may be an experimental artefact, decreasing diversity can have unexpected or no effects on ecosystem properties.

Colony Count, Microbial↗

PubMed2001

Solid waste digestors: process performance and practice for municipal solid waste digestion.

The most common types of anaerobic digesters for solid wastes have been compared based on biological and technical performance and reliability. Batch systems have the most simple designs and are the least expensive solid waste digesters. They have high potential for application in developing countries. Two-stage systems are the most complex and most expensive systems. Their greatest advantage lies in the equalisation of the organic loading rate in the first stage, allowing a more constant feeding rate of the methanogenic second stage. Two-stage systems with biomass accumulation devices in the second stage display a larger resistance toward toxicants and inhibiting substances such as ammonia. However, the large majority of industrial applications use one-stage systems and these are evenly split between "dry" systems (wastes are digested as received) and "wet" systems (wastes are slurried to about 12% total solids). Regarding biological performance, this study compares the different digester systems in terms of organic loading rates and biogas yields considering differences in input waste composition. As a whole, "dry" designs have proven reliable due to their higher biomass concentration, controlled feeding and spatial niches. Moreover, from a technical viewpoint the "dry" systems are more robust and flexible than "wet' systems.

Bacteria, Anaerobic↗

PubMed2003

[Ecophysiological effects of multiple cropping of winter wheat-spring corn-summer corn in Huanghuaihai Plain].

Compared to sequential cropping of winter wheat-summer corn and mono cropping of spring corn, the ecophysiological effects of multiple cropping of winter wheat-spring corn-summer corn in Huanghuaihai Plain were studied. The results showed that under the multi-cropping, the crops occupied higher spatial niches during the period of reproductive growth. Ecological factors such as light, temperature, and air were improved, and plane light acceptance was changed into multistory light acceptance, which made the relative intensity of illumination in crop communities increased. Moreover, soil temperature between rows and wind velocity in planting strips were also increased. All these changes were advantageous to increasing the intensity and velocity of grain filling. The chlorophyll content and photosynthetic rate in functional leaves of crops were higher, which was the main reason of yield increase under multiple cropping.

Agriculture↗

PubMed2004

[Clone growth and its age structure of Leymus secalimus modules in the Songnen Plain of China].

Leymus secalimus, a species of typical clonal plant, is a long-rhizome grass. Under cultivated condition in the Songnen Plain of China, its transplanted single tiller could form 215 tillers at most by vegetative reproduction of a clone in a growth season, and the largest clone was 5.4 times of the smallest one among four sampling clones in the first year. In the second year, the largest clone could form 2852 tillers at most, which was 2.7 times of the smallest one in two growth seasons. At unitary level, the expanding area of the clones and the number of the tillers increased by 13.2 and 13.3 times, respectively, and the accumulative length, nodes number and rhizomes biomass increased by 15.9, 11.2 and 14.7 times averagely by the end of the growth season in the second year than in the first year, respectively. The tillers consisted of two age classes and showed expanding age structure, which was more obvious with the growth of clones. The bud banks consisted of three age classes and showed expanding age structure, which decreased gradually with the growth of clones. The tillers could be developed through forming lots of topmost buds and node buds of rhizome, and the clones achieved the spatial niche expansion and repetitive regeneration.

Biomass↗

PubMed2006

[Functional groups of natural enemies and their temporal-spatial dynamics in jujube orchard intercropped with herbage].

In this paper, an investigation was made on the temporal-spatial dynamics of the functional groups of natural enemies in the jujube orchard 2.5 km west of Taigu (112 degrees 8'E, 38 degrees 9'N, 780 m elevation), Shanxi Province in 2002, aimed to work out an effective strategy to control the pests there. In this orchard, four management modes were applied, i. e., intercropping herbage combined with integrated pest management (IPM), intercropping combined with conventional pest management (CM), intercropping with no pest management (NM), and non- intercropping (CK). The results indicated that the total number of natural enemies in IPM, CM and NM was 187.99%, 151.82% and 210.03% higher than CK, respectively, and the recovery and reconstruction rates as well as the average breadth and overlap indices of two dimensional temporal-spatial niches of the functional groups were higher in intercropping modes than in CK. The average diversity index of the functional groups in intercropping modes was significantly bigger than that in CK, but the fluctuation of the diversity standard error of the functional groups was significantly smaller (P < 0.05). The fluctuation trends of the dominance, diversity, and evenness of functional groups had a significant correlation (P< 0.01) with those of species. These results showed that intercropping herbage in jujube orchard was favorable to the conservation, proliferation, and making use of natural enemies. The natural enemy's community in jujube orchard intercropped with herbage was more stable than that without intercropping, and the numbers and functions of the functional groups were differed with different management modes and different stages. Among the functional groups of natural enemies, ladybirds had a stronger ability of recovery, while spiders and parasitoids were weaker. It was feasible to use functional groups instead of species to study the natural enemy's community in jujube orchard.

Animals↗

PubMed2001

Spatial localization of transplanted hemopoietic stem cells: inferences for the localization of stem cell niches.

The spatial distribution of subpopulations of hemopoietic progenitor cells following syngeneic transplantation was investigated at the single-cell level. The location of infused hemopoietic progenitor cells within the femoral bone marrow of nonablated recipients was determined by 5-(and-6)-carboxyfluorescein diacetate succinimidyl ester labeling of cells and in situ fixation by perfusion. Analysis performed over 15 hours after infusion demonstrated that the spatial distribution of transplanted marrow cells is not a random process. Although the majority of cells enter the bone marrow from the central marrow vessels, the subsequent localization within the bone marrow varied according to their phenotype. Candidate "stem cells" demonstrated selective redistribution and were significantly enriched within the endosteal region, whereas mature terminally differentiated and lineage-committed cells selectively redistributed away from the endosteal region and were predominantly in the central marrow region. Together, these data strongly support historical evidence of the presence of endosteal hemopoietic stem cell niches.

Animals↗

PubMed1999

Niche preferences and spatial distribution of Monogenea on the gills of Pimelodus maculatus in Río de la Plata (Argentina).

Five Monogenea species were found on the gills of the catfish Pimelodus maculatus in Río de la Plata (Argentina). These were used for studying the preference of species on different gill-hemibranches, niche breadth and niche overlap between species. It was found that congeneric species had a generic-specific preference for certain gill-hemibranches. Niche breadth appeared to be related to the number of individuals of each species. Niche overlap between the species is discussed.

Animals↗

PubMed2005

Time-specific ecological niche modeling predicts spatial dynamics of vector insects and human dengue cases.

Numerous human diseases-malaria, dengue, yellow fever and leishmaniasis, to name a few-are transmitted by insect vectors with brief life cycles and biting activity that varies in both space and time. Although the general geographic distributions of these epidemiologically important species are known, the spatiotemporal variation in their emergence and activity remains poorly understood. We used ecological niche modeling via a genetic algorithm to produce time-specific predictive models of monthly distributions of Aedes aegypti in Mexico in 1995. Significant predictions of monthly mosquito activity and distributions indicate that predicting spatiotemporal dynamics of disease vector species is feasible; significant coincidence with human cases of dengue indicate that these dynamics probably translate directly into transmission of dengue virus to humans. This approach provides new potential for optimizing use of resources for disease prevention and remediation via automated forecasting of disease transmission risk.

Aedes↗

PubMed2006

Notch signaling is required to maintain all neural stem cell populations--irrespective of spatial or temporal niche.

Recently, Notch signaling has been reported to underscore the ability of neural stem cells (NSCs) to self-renew. Utilizing mice deficient in presenilin-1(PS1), we asked whether the function of Notch signaling in NSC maintenance was conserved. At embryonic day 14.5, all NSCs--both similar (cortex-, ganglionic eminence- and hindbrain-derived) and distinct (retinal stem cell)--require Notch signaling in a gene-dosage-sensitive manner to undergo expansionary symmetric divisions, as assessed by the clonal, in vitro neurosphere assay. Within the adult, however, Notch signaling modulates cell cycle time in order to ensure brain-derived NSCs retain their self-renewal property. At face value, the effects in the embryo and adult appear different. We propose potential hypotheses, including the ability of cell cycle to modify the mode of division, in order to resolve this discrepancy. Regardless, these findings demonstrate that PS1, and presumably Notch signaling, is required to maintain all NSCs.

Animals↗

PubMed2026

A serpin-myeloid axis in pancreatic cancer heterogeneity and immune evasion.

Pancreatic ductal carcinoma (PDAC) is characterized by a highly immunosuppressive, extracellular matrix-rich microenvironment, yet tumours display marked heterogeneity1-4. This raises the question of whether immune resistance is a global tumour property or is organized within spatially restricted niches. Here, using Perturb-map spatial functional genomics, we determine how different genes shape the growth and cellular environments of PDAC clones across space and time. This analysis revealed early gene-driven remodelling of local immune neighbourhoods preceding late-stage spatial clonal dominance. We identify SERPINE1 (encoding plasminogen activator inhibitor 1 (PAI1)) and SERPINB2 (encoding PAI2) as dominant regulators of tumour microenvironment control and immune evasion. These serpins promote stabilization of fibrin-rich extracellular matrix niches that spatially retain and programme macrophages towards immunosuppressive states while excluding cytotoxic T cells. Loss of Serpine1 or Serpinb2, or pharmacological inhibition of PAI1 or CD18, improves tumour control in mice and synergizes with anti-PD-1. Multimodal spatial analysis of patient tumours revealed that immunosuppressive niches form around rare SERPINB2- and SERPINE1-expressing PDAC subpopulations, dominated by SPP1+/MARCO+ macrophages. These findings identify cancer-derived SERPINE1 and SERPINB2 as local spatial organizers of immune suppression, linking tumour-intrinsic heterogeneity to local microenvironmental control and immunotherapy resistance in PDAC.

Journal Article↗

PubMed2026

Spatial Transcriptomics Identifies Characteristic Immunological Niches in Atopic Dermatitis.

BACKGROUND: Atopic dermatitis (AD) is primarily driven by a Type 2 immune response, with T helper (TH2) cells producing IL-4 and IL-13, thereby promoting inflammation, itch, and a compromised skin barrier. Yet, the spatial organization of pathogenic immune cells and their interactions with stromal and epithelial compartments in human AD skin remain incompletely understood. METHODS: We performed 10× Genomics Visium spatial transcriptomics on FFPE skin biopsies from patients with AD (n = 6), psoriasis (n = 2), and healthy controls (n = 5). Data were integrated with AD single-cell RNA sequencing (scRNA-seq) datasets and complemented by imaging mass cytometry (IMC) and multiplex immunofluorescence (IF) to validate the spatial localization of immune cells. Cell-cell communication analysis revealed putative signaling interactions within immune niches. RESULTS: Spatial clustering resolved tissue compartments and demonstrated transcriptional dysregulation in keratinocytes in AD and psoriasis. AD lesions showed a conserved spatial organization of immune aggregates within the superficial dermis. Integration of scRNA-seq signatures revealed spatially organized co-localization of T cells and mature migratory dendritic cells (mmDCs). We developed a ring-based neighborhood analysis to characterize the cellular organization of the immune-stromal niches, revealing T cell-enriched regions surrounded by inflammatory fibroblasts and activated keratinocytes. Intercellular communication analysis further identified putative signaling within mmDC-T cell niches that may promote pathogenic T cell recruitment and activation. Application of tertiary lymphoid structure (TLS) signatures indicated the presence of TLS-like regions. IMC and IF validated the close spatial proximity between activated TH2 cells and mmDCs. CONCLUSION: AD lesions contain spatially organized TLS-like immune niches at the dermal-epidermal junction, characterized by the close association of T cells and mmDCs and coordinated interactions with surrounding stromal and epithelial compartments. These mmDC-T cell niches may represent potential targets for future therapeutic strategies aimed at disrupting persistent local inflammatory pathways and improving long-term disease control.

atopic dermatitis↗

PubMed2026

Spatial Omics in High-Grade Gliomas: Mapping Immune-Tumor Niches for Precision Therapy.

High-grade gliomas (HGGs), particularly glioblastoma (GBM), remain among the most lethal human cancers despite decades of molecular profiling and therapeutic innovation. A primary reason for treatment failure is that HGG biology is spatial: malignant cell states, immune suppression, metabolic stress, and therapeutic resistance are organized into distinct anatomical and functional niches. Spatial omics technologies now enable high-dimensional mapping of gene expression, protein signaling, immune architecture, and metabolic activity within intact tumor tissue. These approaches reveal how proneural and mesenchymal transcriptional states coexist yet localize to distinct regions, alongside hypoxic, invasive, and stem-enriched niches. Spatial analyses show that key clinical determinants, including O6-methylguanine-DNA methyltransferase (MGMT)-associated temozolomide resistance, radiotherapy tolerance in hypoxic regions, and immunotherapy failure driven by myeloid-dominated immune exclusion, are influenced not only by molecular programs but also by cellular location. Beyond biological insight, spatial omics is reshaping clinical paradigms by enabling region-specific patient stratification, early assessment of treatment response, and identification of therapy-resistant reservoirs that seed recurrence. Prior bulk and single-cell studies defined HGG cell states and pathways but often treated resistance as tumor-wide. This review presents a spatially explicit framework that synthesizes spatial transcriptomic and immune-profiling studies to identify tumor-immune niches and spatial bottlenecks that drive therapeutic failure and recurrence.

Humans↗

PubMed2006

Spatial effects favour the evolution of niche construction.

We present an individual-based, spatial implementation of an existing two-locus population genetic model of niche construction. Our analysis reveals that, across a broad range of conditions, niche-construction traits can drive themselves to fixation by simultaneously generating selection that favours 'recipient' trait alleles and linkage disequilibrium between niche-construction and recipient trait alleles. The effect of spatiality is key, since it is the local, resource-mediated interaction between recipient and niche-constructing loci which gives rise to gene linkage. Spatial clustering effects point to a possible mechanism by which an initially rare recipient trait whose selection depends on niche construction could establish in an otherwise hostile environment. The same mechanism could also lead to the spread of an established niche-constructing colony. Similar phenomena are observed in the spatial modelling of two species 'engineering webs'. Here, the activities of two niche-constructing species can combine to drive a particular recipient trait to fixation, or in certain circumstances, maintain the presence of polymorphisms through the preservation of otherwise deleterious alleles. This may have some relevance to ecosystem stability and the maintenance of genetic variation, where the frequencies of key resources are affected by the niche-constructing activities of more than one species. Our model suggests that the stability of multi-species webs in natural populations may increase as the complexity of species-environment interactions increases.

Biological Evolution↗