Population Niche Research Articles

Pelagic and benthic ecosystems drive differences in population and individual specializations in marine predators.

Individual specialization, which describes whether populations are comprised of dietary generalists or specialists, has profound ecological and evolutionary implications. However, few studies have quantified individual specialization within and between sympatric species that are functionally similar but have different foraging modes. We assessed the relationship between individual specialization, isotopic niche metrics and foraging behaviour of two marine predators with contrasting foraging modes: pelagic foraging female South American fur seals (Arctocephalus australis) and benthic foraging female southern sea lions (Otaria byronia). Stable isotope analysis of carbon and nitrogen was conducted along the length of adult female vibrissae to determine isotopic niche metrics and the degree of individual specialization. Vibrissae integrated time ranged between 1.1 and 5.5years, depending on vibrissae length. We found limited overlap in dietary niche-space. Broader population niche sizes were associated with higher degrees of individual specialization, while narrower population niches with lower degrees of individual specialization. The degree of individual specialization was influenced by pelagic and benthic foraging modes. Specifically, South American fur seals, foraging in dynamic pelagic environments with abundant but similar prey, comprised specialist populations composed of generalist individuals. In contrast, benthic southern sea lions foraging in habitats with diverse but less abundant prey had more generalist populations composed of highly specialized individuals. We hypothesize that differences in specialization within and between populations were related to prey availability and habitat differences. Our study supports growing body of literature highlighting that individual specialization is a critical factor in shaping the ecological niche of higher marine predators.

Role of SCF-Expressing Bone Marrow Populations in Hematopoietic and Leukemic Stem Cell Regulation

Stem cell factor (SCF), the ligand for the c-Kit receptor, stimulates growth of early hematopoietic stem/progenitors cells (HSCs) directly and/or by stimulating other cytokines. Using transgenic and driver/reporter mice, studies have shown that, in physiological conditions the Scf gene is expressed in bone marrow microenvironmental (BMM) cells, in particular endothelial and perivascular stroma. Deletion of exon 1 from the Scf gene in endothelial cells (using Tek-cre), perivascular cells (using Lepr-cre) and adipocytes (using adipoq-cre) significantly reduced the frequency and function of hematopoietic stem cells (HSCs) in young adult mice (Zhou et al. Nature cell biology. 2017; Ding et al. Nature. 2013). These studies have been useful in identifying the different Scf-expressing niche compartments from the BMM that are important for HSC maintenance. However, leukemic stem cell (LSC ) regulation by specific BMM cells in CML is poorly understood. In our study, the different Scf-expressing niche populations were identified using the Scf-GFP knock-in model (Scfgfp/+). CD45-TER119-CD31-CD140+ (PαS) and CD45-TER119-CD31-CD51+CD105+6C3+ (6C3) populations, representing mesenchymal progenitors and HSC-supporting stromal cells, respectively, showed the highest levels of Scf expression in normal mice, with endothelial cells also expressing SCF but at a lower level. We confirmed the role of Scf in normal hematopoiesis by showing that Scff/f - Ubc-cre mice generated by crossing Scff/f mice (LoxP sites flanking exon 1) with Ubc-cre mice (Cre mediated excision in widespread tissues following Tamoxifen administration) showed decreased stem/progenitor counts. To further evaluate the contribution of Scf-expressing populations towards regulation of normal HSC and LSCs, the Scff/f mice (LoxP sites flanking exon 1) were crossed with Bglap-cre (osteoblasts), Osx-cre (osteoprogenitors), Prx1-cre (mesenchymal progenitors) and Tek-cre (endothelial cells) mice. Deletion of Scf in the target populations was confirmed. We observed markedly reduced long-term HSC (LT-HSC; Lin-Sca-1+Kit+CD48-CD150+) numbers in the BM of 4-week old Scff/f-Prx1-cre mice, and to a lesser extent in Scff/f - Bglap-cre mice, and reduced short-term HSC (ST-HSC; Lin-Sca-1+Kit+CD48-CD150-). We observed markedly reduced ST-HSC numbers, and LT-HSC to a lesser extent, in the BM of 4-week old Scff/f - Osx-cre mice, supporting a role for these Scf -expressing populations in normal HSC maintenance in developing animals. In contrast to previous reports, we did not observe changes in stem/progenitor numbers in Tek-cre animals. To further evaluate effects of Scf-expressing niche populations on regulation of normal HSC and CML LSC, BM cells from wild-type (1x106 CD45.1 cells) and SCL-tTA-BCR-ABL mice (1x106 CD45.1/2) were transplanted into irradiated (8Gy) Scff/f Cre- or Cre+ knockout animals and followed for hematopoietic reconstitution. Scff/f-Prx1-cre animals showed decreased numbers of normal LT-HSC and ST-HSC in the BM compared to WT mice, but did not show changes in CML LSC numbers, although BM and peripheral blood (PB) myeloid counts were reduced. Scff/f - Osx-cre mice showed decreased numbers of ST-HSC, but no changes in changes in normal HSC or CML LSC were seen. Scff/f-Bglap-cre mice did not show significant reduction in normal and CML LT-HSC in BM. Collectively, our results show that Scf -expressing mesenchymal stem cells play an important role in normal LT-HSC maintenance, and osteoprogenitors in normal ST-HSC maintenance. In contrast, CML LSCs are not dependent on SCF expression on the different mesenchymal populations studied here. Therefore, normal and leukemic stem cells appear to be differentially regulated by SCF-expressing BMM populations. Further studies to better define the Scf -expressing populations that support CML LSCs, and the effects of SCF-expressing BMM populations on LSC response to tyrosine kinase inhibitors are underway. DisclosuresNo relevant conflicts of interest to declare.

Maternal effects and fitness consequences of individual variation in bottlenose dolphins' ecological niche.

The niche describes the ecological and social environment that an organism lives in, as well as the behavioural tactics used to interact with its environment. A species niche is key to both ecological and evolutionary processes, including speciation, and has therefore been a central focus in ecology. Recent evidence, however, points to considerable individual variation in a species' or population's niche use, although how this variation evolves or is maintained remains unclear. We used a large longitudinal dataset to investigate the drivers and maintenance of individual variation in bottlenose dolphins' Tursiops aduncus niche. Specifically, we (a) characterised the extent of individual differences in habitat use, (b) identified whether there were maternal effects associated with this variation and (c) investigated the relationship between habitat use and calving success, a component of reproductive fitness. By examining patterns of habitat use, we provide evidence that individual dolphins vary consistently between one another in their niche. We further show that such individual variation is driven by a strong maternal effect. Finally, habitat use and calving success were not related, suggesting that use of different habitats results in similar fitness outcomes. Niche partitioning, maintained by maternal effects, likely facilitates the coexistence of multiple ecotypes within this population.

Integrated OMICs unveil the bone-marrow microenvironment in human leukemia.

SummaryThe bone-marrow (BM) niche is the spatial environment composed by a network of multiple stromal components regulating adult hematopoiesis. We use multi-omics and computational tools to analyze multiple BM environmental compartments and decipher their mutual interactions in the context of acute myeloid leukemia (AML) xenografts. Under homeostatic conditions, we find a considerable overlap between niche populations identified using current markers. Our analysis defines eight functional clusters of genes informing on the cellular identity and function of the different subpopulations and pointing at specific stromal interrelationships. We describe how these transcriptomic profiles change during human AML development and, by using a proximity-based molecular approach, we identify early disease onset deregulated genes in the mesenchymal compartment. Finally, we analyze the BM proteomic secretome in the presence of AML and integrate it with the transcriptome to predict signaling nodes involved in niche alteration in AML.

Hybridization, ecogeographical displacement and the emergence of new lineages – A genotyping‐by‐sequencing and ecological niche and species distribution modelling study of Sempervivum tectorum L. (Houseleek)

Ecogeographical displacement of homoploid hybrid lineages from their parents is well documented and considered an important mechanism to achieve reproductive isolation. In this study, we investigated the origin of the flowering plant species Sempervivum tectorum in the Massif Central (France) through homoploid hybridization between lineages of the species from the Rhine Gorge area (Germany) and the Pyrenees (France). We used genotyping-by-sequencing genetic data as evidence for the hybrid origin of the Massif Central lineage, and WorldClim climatic data and soil pH and soil temperature data collected by us for ecological niche and species distribution modelling. We could show that the Massif Central lineage shows hybrid admixture and that the niche of this lineage is significantly different from those of the parental lineages. In comparison with the parental niches, different variables of the niche of the hybrid lineage are intermediate, parental-combined or extreme. The different niche of the Massif Central populations thus can plausibly be interpreted as hybridization-derived. Our species distribution modelling for the Last Glacial Maximum and Mid-Holocene showed that the potential distribution of the hybrid lineage at the likely time of its origin in the Quaternary possibly was parapatric in relation to the largely sympatric distributions of the parental lineages. We hypothesize that reproductive isolation of the hybrid lineage from the parental lineages resulted from the segregation of distribution ranges by a differential response of the three lineages to a warming climate.

Casting Light on the Adaptation Mechanisms and Evolutionary History of the Widespread Sumerlaeota.

Sumerlaeota is a mysterious, putative phylum-level lineage distributed globally but rarely reported. As such, their physiology, ecology, and evolutionary history remain unknown. The 16S rRNA gene survey reveals that Sumerlaeota is frequently detected in diverse environments globally, especially cold arid desert soils and deep-sea basin surface sediments, where it is one dominant microbial group. Here, we retrieved four Sumerlaeota metagenome-assembled genomes (MAGs) from two hot springs and one saline lake. Including another 12 publicly available MAGs, they represent six of the nine putative Sumerlaeota subgroups/orders, as indicated by 16S rRNA gene-based phylogeny. These elusive organisms likely obtain carbon mainly through utilization of refractory organics (e.g., chitin and cellulose) and proteinaceous compounds, suggesting that Sumerlaeota act as scavengers in nature. The presence of key bidirectional enzymes involved in acetate and hydrogen metabolisms in these MAGs suggests that they are acetogenic bacteria capable of both the production and consumption of hydrogen. The capabilities of dissimilatory nitrate and sulfate reduction, nitrogen fixation, phosphate solubilization, and organic phosphorus mineralization may confer these heterotrophs great advantages to thrive under diverse harsh conditions. Ancestral state reconstruction indicated that Sumerlaeota originated from chemotrophic and facultatively anaerobic ancestors, and their smaller and variably sized genomes evolved along dynamic pathways from a sizeable common ancestor (2,342 genes), leading to their physiological divergence. Notably, large gene gain and larger loss events occurred at the branch to the last common ancestor of the order subgroup 1, likely due to niche expansion and population size effects.IMPORTANCE In recent years, the tree of life has expanded substantially. Despite this, many abundant yet uncultivated microbial groups remain to be explored. The candidate phylum Sumerlaeota is widely distributed in various harsh environments. However, their physiology, adaptation mechanisms, and evolution remain elusive due to a lack of pure cultures and limited available genomes. Here, we used genomes from uncultivated members of Sumerlaeota to disclose why these taxa can thrive under diverse harsh conditions and how they evolved from a chemotrophic and facultatively anaerobic common ancestor. This study deeply explored the biology of Sumerlaeota and provided novel insights into their possible roles in global biogeochemical cycles, adaptation mechanisms, ecological significance, and evolutionary history.

Towards ecosystem integration for a better understanding of aggressiveness of B-cell lymphomas.

Towards ecosystem integration for a better understanding of aggressiveness of B-cell lymphomas.

Quantifying temporal variation in dietary niche to reveal drivers of past population declines

Abstract Given the long and dynamic history of anthropogenic disturbances to ecosystems, it is difficult to determine the drivers of past population declines. These uncertainties dilute the efficacy of conservation efforts and might hinder species and ecosystem recovery. Niche quantification can be a useful tool for understanding drivers of past population declines. Niche parameters reflect key resources used, providing insight into the conditions needed to achieve population stability. By reconstructing a population's niche position and space over a period of decline and comparing to historic baselines, shifts in the realized niche of a species can be assessed. Comparing shifts to historic information on resource availability and timing of declines can allow practitioners to identify probable drivers of species decline. We demonstrated the utility of this technique by reconstructing parameters of isotopic dietary niche over a 130‐year period and comparing isotopic niche reconstructions to land use and crop harvests during this same period via regression and Bayesian standard ellipsoid (SIBER) analyses. We use a formerly widespread but now endangered species, the eastern spotted skunk Spilogale putorius, addressing the hypothesis that land use change and agricultural intensification led to a historical collapse of key dietary resources which correlates with population declines in this species. To help control for isotopic variability unrelated to population decline, we compare trends to those of a secure, but ecologically similar generalist mesocarnivore, the striped skunk Mephitis mephitis, across the same spatiotemporal scale. We present evidence that historic dietary changes occurred in spotted skunks in the early 1900s but not to the same degree in striped skunks. Changes in isotopic composition correspond with the temporal period of decline and are explained by concurrent changes in land use. These results support the hypothesis that loss of key dietary resources as a result of land use change and agricultural intensification played a significant role in population declines of spotted skunks in this region. A free Plain Language Summary can be found within the Supporting Information of this article.

Asymmetric Evolvability Leads to Specialization without Trade-Offs.

AbstractMany organisms are specialized, and these narrow niches are often explained with trade-offs-the inability for one organism to express maximal performance in two or more environments. However, evidence is lacking that trade-offs are sufficient to explain specialists. Several lines of theoretical inquiry suggest that populations can specialize without explicit trade-offs, as a result of relaxed selection in generalists for their performance in rare environments. Here, I synthesize and extend these approaches, showing that emergent asymmetries in evolvability can push a population toward specialization in the absence of trade-offs and in the presence of substantial ecological costs of specialism. Simulations are used to demonstrate how adaptation to a more common environment interferes with adaptation to a less common but otherwise equal alternative environment and that this interference is greatly exacerbated at low recombination rates. This adaptive process of specialization can effectively trap populations in a suboptimal niche. These modeling results predict that transient differences in evolvability across traits during a single episode of adaptation could have long-term consequences for a population's niche.

Seasonal isotopic niche of a rodent: High between‐individual variation but no changes in individual niche width during the rich‐resource period

AbstractThe dynamics of trophic niche width in animals at both population level and individual level is potentially influenced by temporal variation of food resources, by between‐individual differences in food‐resource rank preferences, and also by competition. Using stable isotope of carbon and nitrogen (δ13C and δ15 N) of fecal samples, we investigated the trophic niche dynamics and individual variation in food‐resource use by the arboreal rat Rhipidomys macrurus, in the highly seasonal Brazilian savanna (Cerrado). We tested the hypothesis that dietary niche expansion during the rich‐resource period (wet season) occurs via individual specialization and consequently lower individual niche overlap in contrast with niche retraction during the low‐resource period (dry season) via increase in niche overlap and expansion of individual niches. The results indicated that R. macrurus is primarily frugivorous and presents a wider isotopic niche in the rich‐resource period in comparison with the low‐resource period. The increase in niche width was achieved by individual specialization (decrease in niche overlap), as expected. During the low‐resource period, however, individual niche widths were not wider than during the rich‐resource period. Additionally, individual body condition was lower in the wet season than in the dry season, suggesting higher competition in this period. We conclude that an increase in the population niche may involve only between‐individual variation and not necessarily requiring changes in individual niche width. We propose that the combination of ecological opportunity (high resource diversity) in addition to a greater competition in the warm–wet season leads to expansion of the population trophic niche width via individual specialization.Abstract in Portuguese is available with online material.

Constraining the Likely Technological Niches of Late Middle Pleistocene Hominins with Homo naledi as Case Study

We develop a framework to differentiate the technological niches of co-existing hominin species by reviewing some theoretical biases influential in thinking about techno-behaviours of extinct hominins, such as a teleological bias in discussing technological evolution. We suggest that some stone-tool classification systems underestimate technological variability, while overestimating the complexity of the behaviours most commonly represented. To model the likely technological niches of extinct populations, we combine ecological principles (i.e. competitive exclusion) with physical anthropology and the archaeological record. We test the framework by applying it to the co-existence of Homo naledi and Homo sapiens during the late Middle Pleistocene in southern Africa. Based on our analysis, we suggest that tool use was probably not an essential part of H. naledi’s niche, but that technology occasionally provided caloric benefits. In contrast, tool use was a structural part of the H. sapiens way of life. We provide reasoning for our interpretation that the latter population is associated with more sophisticated reduction strategies and the development of prepared core technology. The method also has applicability to cases such as the co-existence of different toolmakers during the Earlier Stone Age (ESA) in East Africa and the co-existence of Neanderthals and H. sapiens in Eurasia.

La temperatura y radiación solar explican diferencias en la distribución de dos árboles altoandinos (Polylepis spp.) localmente simpátricos en la Cordillera Blanca, Perú

ABSTRACT Knowledge of the ecological requirements, the current extensions, and cover of a species is important for its management conservation, but this information is lacking for many species of Polylepis (ROSACEA). Here we use niche modeling to understand the ecological requirements of two Polylepis species natively found in sympatry within the Huascarán National Park (HNP) (Cordillera Blanca, Peru), Polylepis albicans and P. webebaueri, and produce species distribution maps restricted by forest cover to estimate each species' current cover within the park . Based on presence/absence data collected systematically throughout their local elevational distribution and analyzed using a Canonical Correspondence Analysis (CCA) and generalized linear models (glm), the best models show that P. albicans and P. weberbaueri have different environmental niches and their occupation is maximized at different climatic ranges mainly associated with temperature (annual mean temperature and mean monthly temperature range) and solar radiation during the dry season. P. albicans occupies warmer and drier areas than P. weberbaueri, which leads to a spatial segregation that has implications for the conservation management of each species. However, it is necessary to evaluate if the models described here adequately capture the environmental niche of other populations of P. weberbaueri, or if these could be new species. Our results indicate that within the HNP, the extension of Polylepis forests (~ 24,000 ha; 11,361 ha of P. albicans and 12,627 ha of P. weberbaueri) is significantly greater than that previously reported and confirm that this protected area harbors the greatest extensions of both species in Peru and its proper management is key for their conservation and that of the ecosystems they constitute.

«СТЕПНЫЕ КОРИДОРЫ» АЛАКУЛЬСКИХ СКОТОВОДОВ: РЕЗУЛЬТАТЫ ИЗОТОПНЫХ И ПАЛЕОБОТАНИЧЕСКИХ ИССЛЕДОВАНИЙ НА ПОСЕЛЕНИИ ЧЕБАРКУЛЬ III

The paper is devoted to the determination of the preferred ecological niche of the Alakul population of the forest-steppe Trans-Urals and considers the problem of Andronovo colonization in the northern direction. Radiocarbon dating, paleobotanical and isotopic studies were carried out based on the Chebarkul III settlement materials. The Alakul period of the settlement dates back to the 18th–17th centuries BC. The species composition of plants from the settlement’s cultural layer is similar to the Bronze Age steppe settlements of the Southern Trans-Urals and mainly represented by plant seeds of the meadow and ruderal zones with a minimum amount of forest and the absence of domesticated plants. The δ13C, δ15N values in the livestock bones reflect the diet consisting of C3 photosynthesis type plants with a small proportion of C4 plants. The decreased values of δ13C and δ15N in comparison with the Late Bronze Age steppe sites in the Ural-Kazakhstan region may indicate a high moisture content of the settlement’s pastures. The data obtained indicate the preservation of the settled cattle-breeding model, which is typical for the steppe Alakul sites, with cattle grazing in the surrounding territories and the possible preparation of fodder for the winter. The development of northern territories by the Alakul populations took place in the landscape zones habitual for the steppe population: with the presence of open spaces, wide meadows for grazing animals, and preparing forage, as well as forests. For this reason, the so-called Chebarkul steppe corridor was also populated, capturing the shore of the lake of the same name, on which the settlement under study is located.

Propagule establishment and seedling growth in a shifting mangrove population: performance in novel tidal conditions

Survival and establishment of mangrove propagules at tidal elevations beyond the landward margin of their distribution underlie continued existence of mangroves in response to sea-level rise. Yet few studies have empirically examined mangrove performance at higher intertidal positions (novel sites) into which mangroves disperse. We compared propagule establishment and seedling growth at 2 intertidal elevations for black mangroves Avicennia germinans displaying landward expansion. Propagule survival, establishment success, and growth rate of seedlings were monitored for 158 d during a reciprocal transplant experiment targeting 2 tidal elevations: one within the current niche of the mangrove population (LOW) and one representing marginal habitat where mangroves have begun migration upland (MID). We introduced propagules to 4 treatments: (1) originating (site of parent tree) at LOW, stranding at MID; (2) originating at MID, stranding at LOW; (3) and (4) stranding and originating at the same position (MID or LOW). Resident and transplant propagules of MID origin were 22 times more likely to die during the first 33 d than propagules of LOW origin. Resident and transplant propagules in MID positions were 6.5 times more likely to die over the first 33 d than individuals in LOW positions. After seedling establishment, no mortality was observed in LOW or MID positions. Thus, environmental conditions of novel intertidal areas into which black mangroves migrate had a greater deleterious impact on propagules than on seedlings. Identifying processes underlying success of mangroves introduced into novel environments, such as those operating as sea level rises, will require increased attention to the fate of propagules.

Individual specialists within a generalist niche: variable diet of stoats and implications for conservation

Conservation programmes aiming to suppress or remove invasive small mammal populations that threaten endemic fauna assume that eliminating an individual predator has the same effect as eliminating a conspecific in terms of decreasing risk to the prey species. However, marked between-individual variation in prey take could, at times, lead to uneven predation pressure. Such variation in the diets of introduced predators has long been hypothesised in New Zealand, suggesting that some observed rates of predation are not typical of the prey population as a whole. We used stable isotope analysis to estimate the isotopic dietary niches of stoats Mustela erminea (n = 51) caught in three New Zealand National Parks. We modelled δ13C and δ15N ratios from five tissue types to estimate the isotopic niche for each individual stoat, and for each population. The isotopic niche used by the population of stoats in Nelson Lakes National Park was substantially larger (5.3 ‰2) than for those at either Mt Aspiring National Park (3.1 ‰2) or Fiordland National Park (2.8 ‰2). Despite this, a measure of individual specialisation (proportional niche use) in stoats at Nelson Lakes National Park (0.4 ± 0.3) was similar to the other two sites. Collectively these data suggest a comparable degree of individual specialisation even within a more generalist population niche. This variability in the range of prey items taken by small carnivores, between populations and individuals of the same species, has consequences for how we design and monitor small mammal control programmes; for example, the threatened species outcomes observed in one area or time period may not be applicable to another.

Genotypes of the Cacoecia Podana Sc. Larvae in the Aes-1 Esterase Locus Differ in Their Food Micro-Niches

Intergenotypic differentiation of trophic niche was studied in the system “apricot (Prunus armeniaca L.) - Cacoecia podana Sc.”. C. podana larvae, carried alternative Aes-1 genotypes, were found to prefer host plant leaves, differing by length and stiffness, in their diets. Trophic micro-niches for each genotype coincided with the whole population niche in width, but differed by their optimums. There data are discussed in respect to the herbivore food specialization and population dynamics.

Food niche of solitary and social bees (Hymenoptera: Apoidea) in a Neotropical Savanna

In this study we investigated the group of floral resources that support bee populations from a bee assemblage in a savanna, and the way in which bee species use these food resources, with an emphasis on the breadth and overlap of trophic niches. The interactions between 75 species of bees and 62 species of plants visited to obtain floral resources were recorded on a Brazilian savanna site. The bee species explored a diverse set of plant species, but concentrated the collection of resources in a few plant species. The distribution of the samples over a long period favored a robust characterization of the food niche of the bee populations. Byrsonima sericea, Serjania faveolata, and Stigmaphyllon paralias were the plant species with the highest number of links with bees. In general, the trophic niche overlap was low, with 75% of pairs of bee species having a niche overlap (NO) less than 0.33. Only four pairs showed high overlap (NO>0.70) and all cases were related to the exploitation of floral resources provided by B. sericea, a key resource for the maintenance of the local bee fauna, an oil and pollen provider.

Victoria L. Sork—Recipient of the 2020 Molecular Ecology Prize

Victoria L. Sork—Recipient of the 2020 Molecular Ecology Prize

How to Become a Generalist Species? Individual Niche Variation Across Habitat Transformation Gradients

Species in transformed habitats, frequently labeled as environmental generalists, tend to show broader niches than species in natural habitats. However, how population niche expansion translates into changes in the niches of individual organisms remains unclear, particularly in the context of habitat transformation. Niche expansion could be a product of individuals having broader niches, greater distances among individuals’ niches, or a combination of both processes. This would challenge the traditional conceptions on niche dynamics, which emphasize the role played by individual specialization (IS). Here, using stable isotopes, we computed total niche width (TNW), its within- and between-individual components (WIC and BIC), and IS (the ratio WIC/TNW), in 13 populations of 6 bird species and 8 populations of 3 frog species in natural and transformed habitats. We confirmed that species had broader niche width in transformed than in natural habitats, yet population niche expansion across habitats was mainly a product of increased distance between individuals. Within each habitat type, increases in TNW were linked to increases in WIC for all habitat types, while relationships between TNW and BIC were found in transformed but not in natural habitats. Hence, both increased individual niche width and increased distance among individuals were apparent within habitats, particularly in transformed ones, where increases in WIC dominated. Neither across or within habitats was niche expansion associated with increasing IS. Therefore, our results overturn traditional conceptions associated with the niche variation hypothesis and illustrate that niche expansion is not invariably associated with increased IS, because the distance between individual’s niches (BIC) can increase, as well as the breadth of those niches (WIC).

Checkpoint inhibitors first in patients with metastatic non-small cell lung cancer harboring BRAFV600E mutation with PD-L1 90%—a debate in a niche population

Checkpoint inhibitors first in patients with metastatic non-small cell lung cancer harboring BRAFV600E mutation with PD-L1 90%—a debate in a niche population