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1. The geographical range sizes of individual species vary considerably in extent, although the factors underlying this variation remain poorly understood, and could include a number of ecological and evolutionary processes. A favoured explanation for range size variation is that this result from differences in fundamental niche breadths, suggesting a key role for physiology in determining range size, although to date empirical tests of these ideas remain limited. 2. Here we explore relationships between thermal physiology and biogeography, whilst controlling for possible differences in dispersal ability and phylogenetic relatedness, across 14 ecologically similar congeners which differ in geographical range extent; European diving beetles of the genus Deronectes Sharp (Coleoptera, Dytiscidae). Absolute upper and lower temperature tolerance and acclimatory abilities are determined for populations of each species, following acclimation in the laboratory. 3. Absolute thermal tolerance range is the best predictor of both species' latitudinal range extent and position, differences in dispersal ability (based on wing size) apparently being less important in this group. In addition, species' northern and southern range limits are related to their tolerance of low and high temperatures respectively. In all cases, absolute temperature tolerances, rather than acclimatory abilities are the best predictors of range parameters, whilst the use of independent contrasts suggested that species' thermal acclimation abilities may also relate to biogeography, although increased acclimatory ability does not appear to be associated with increased range size. 4. Our study is the first to provide empirical support for a relationship between thermal physiology and range size variation in widespread and restricted species, conducted using the same experimental design, within a phylogenetically and ecologically controlled framework.

Macroevolutionary and microevolutionary studies provide complementary explanations of the processes shaping the evolution of niche breadth. Macroevolutionary approaches scrutinize factors such as the temporal and spatial environmental heterogeneities that drive differentiation among species. Microevolutionary studies, in contrast, focus on the processes that affect intraspecific variability. We combine these perspectives by using macroevolutionary models in a comparative study of intraspecific variability. We address potential differences in rates of evolution of niche breadth and position in annual and perennial plants of the Eriogonoideae subfamily of the Polygonaceae. We anticipated higher rates of evolution in annuals than in perennials owing to differences in generation time that are paralleled by rates of molecular evolution. Instead, we found that perennial eriogonoid species present greater environmental tolerance (wider climate niche) than annual species. Niche breadth of perennial species has evolved two to four times faster than in annuals, while niche optimum has diversified more rapidly among annual species than among perennials. Niche breadth and average elevation of species are correlated. Moreover, niche breadth increases more rapidly with mean species elevation in perennials than in annuals. Our results suggest that both environmental gradients and life-history strategy influence rates and patterns of niche breadth evolution.

AIM: To test the niche breadth hypothesis (NBH), which states that dominant species have broader environmental tolerances than rare species, focusing on oligarchic species distributions (1) along the gradients of edaphic and climatic individual variables, and (2) within the n‐dimensional environmental frame defined by all edaphic and climatic variability. LOCATION: Amazonian and Andean tropical rain forests along a ca. 3000 m elevation gradient, covering an area of 200 × 200 km in northwestern Bolivia. METHODS: All woody plants with a DBH ≥2.5 cm were measured in 98 0.1‐ha plots. We analysed 18 chemical properties of the soils in each plot. Climatic and topographic variables were obtained from available open‐access databases. Three measures were calculated for each of the species found at each forest type: (1) regional‐scale dominance based on frequency and local abundance, (2) niche breadth along each of the environmental variables, and (3) total niche size within the whole environment. RESULTS: Oligarchic species showed broader niche breadths than the other species that constituted the community assembly in both Amazonian and Andean rain forests. The niche breadth of any species tended to be positively correlated with its degree of dominance. The Amazonian forest showed a stronger oligarchic pattern than the Andean forest, and the Amazonian common species showed larger niches overall. However, this pattern differed for some particular variables: Amazonian oligarchies had narrower niches along the variables related to organic matter and most climatic variables, whereas Andean oligarchies had narrower niches along several micronutrient factors and temperature variables. CONCLUSIONS: The results provide strong empirical support for the NBH in tropical rain forests. However, different patterns of dominance were found in the two habitats: oligarchic species ranged from narrow‐niched species to very broad generalist species. Broad‐niched oligarchic species have also been reported in other regions, suggesting an important role of niche size linking commonness at different scales. Oligarchic species exhibit relatively narrow niches with respect to soil factors if measured along wide gradients, regardless of the forest type studied. In contrast, the opposite pattern was found for many climatic variables, indicating higher sensitivity to climate in Amazonia compared to the Andes. Despite these differences, Amazonia has much larger total niche sizes for its common species than the Andes overall.

The ecological niche is a key concept for elucidating patterns of species distributions and developing strategies for conserving biodiversity. However, recent times are seeing a widespread debate whether species niches are conserved across space and time (niche conservatism hypothesis). Biological invasions represent a unique opportunity to test this hypothesis in a short time frame at the global scale. We synthesized empirical findings for 434 invasive species from 86 studies to assess whether invasive species conserve their climatic niche between native and introduced ranges. Although the niche conservatism hypothesis was rejected in most studies, highly contrasting conclusions for the same species between and within studies suggest that the dichotomous conclusions of these studies were sensitive to techniques, assessment criteria, or author preferences. We performed a consistent quantitative analysis of the dynamics between native and introduced climatic niches reported by previous studies. Our results show there is very limited niche expansion between native and introduced ranges, and introduced niches occupy a position similar to native niches in the environmental space. These findings support the niche conservatism hypothesis overall. In particular, introduced niches were narrower for terrestrial animals, species introduced more recently, or species with more native occurrences. Niche similarity was lower for aquatic species, species introduced only intentionally or more recently, or species with fewer introduced occurrences. Climatic niche conservatism for invasive species not only increases our confidence in transferring ecological niche models to new ranges but also supports the use of niche models for forecasting species responses to changing climates.

AimsUnderstanding the ecological impacts of biological invasions is a core issue of invasion ecology. Soil microbiomes control the functioning and health of ecosystems. The aim of this study was to uncover the changes in the soil microbiome caused by invasive plant expansion.MethodsTaking the typical invasive plant Alternanthera philoxeroides as an example, the structure, diversity, co-occurrence patterns, habitat niche breadth, and assembly processes of the microbiome in invasion-present and invasion-absent soils were analyzed based on high-throughput sequencing.ResultsThe invasion altered the structure and composition of the soil microbiome significantly. A group of biomarkers was established using the random-forest machine-learning model to best represent the differences in the microbiome between the invasion-present and invasion-absent soils. The plant invasion decreased the beta-diversity of the soil microbiome but increased the alpha-diversity. Compared with the invasion-absent soils, the invasion-present soils had a more complex and robust network with more keystone species, fewer modules, and more co-occurring associations. The microbiome in the invasion-present soils had a wider habitat niche breadth, with a higher proportion of habitat generalists and lower proportion of habitat specialists. Finally, the importance of stochasticity in the community assembly increased in the invasion-present soils, although deterministic processes still played a dominant role.ConclusionThis study reveals the consequences to the soil microbiome of the expansion of invasive plants, which is of great significance for an in-depth understanding of the ecological impacts of plant invasion and soil-microbe ecological processes.

ABSTRACT Aim Niche conservatism and niche shift, as two opposing ecological processes influencing invasive species spread, pose challenges for developing management strategies in China. However, how these mechanisms interact during invasion remains unclear. We propose that this uncertainty stems from species traits and invasion histories. Specifically, compared to weak invasive and non‐invasive alien plants, we hypothesize that vigorous invasive plants in China are more likely to exhibit niche shifts. Location China. Methods We quantified the niche dynamics of three categories of alien plant species in China using PCA and their driving factors, while simultaneously predicting their potential distributions with the MaxEnt model. Results Annual mean temperature (Bio1), maximum temperature of the warmest month (Bio5), and precipitation of the driest month (Bio14) were identified as key environmental variables. Most alien plant species exhibited strong niche conservatism. Vigorous and weak invaders showed higher niche stability, lower unfilling, and lower pioneering, whereas non‐invaders displayed higher niche expansion, unfilling, and pioneering. The niche centroids of most species shifted toward warmer, drier, and lower‐elevation areas with more intensive human activity. Longer residence time was associated with lower niche unfilling across all three species categories. Propagule pressure promoted niche filling in vigorous and weak invaders. Species with broader native ranges exhibited higher niche stability. MaxEnt models indicated that vigorous and weak invaders had extensive potential distributions, while non‐invaders were more restricted. Main Conclusion The invasion success of alien plants in China mainly depends on niche conservatism and effective niche filling rather than extensive niche expansion. Long‐term residence and strong propagule pressure promote the occupation of potential habitats. Native niche breadth has a positive effect on niche conservatism. These findings provide a scientific basis for the monitoring, risk assessment, and management of alien plants.

ABSTRACT Genome size is an adaptive trait, and its variations influence the organismal phenotype and fitness. In this study, we propose a hypothesis linking variations in genome size within Scolopendra to ecological factors. To test this hypothesis, we employed flow cytometry to estimate genome size in seven Scolopendra species from Chinese mainland. Subsequently, we reconstructed the phylogenetic relationship of these species using the cytochrome c oxidase subunit 1 gene and conducted phylogenetic comparative analysis to assess the relationships between genome size and niche breadth or 19 bioclimatic variables. Our findings indicate the following: (1) genome size in Scolopendra can be categorized into three groups, similar to the phylogenetic clades; (2) there is a negative correlation between genome size in Scolopendra species and the precipitation niche breadth of species; (3) the estimated divergence time of Scolopendra dates back 153 Mya, during the Jurassic period. We assume that consistent aridity geological periods may promote the evolution of Scolopendra species with a large genome size, whereas rapidly fluctuating humidity geological periods may have the opposite effect. Genome size in Scolopendra can be categorized into three groups that align with the phylogenetic clades; there is a negative correlation between genome size in Scolopendras and the precipitation niche breadth of species; the estimated divergence‐time of Scolopendra dates back 153 Mya, during the Jurassic period.

Understanding the trophic and demographic dynamics of apex predators is of paramount importance for ecosystem conservation. Apex predators are usually free from predation, and thus, the main driver of population dynamics is the availability of trophic resources, which affects breeding performance. Albeit food habits have been described in many apex species, the effects of changes in the trophic niche on long‐term demographic dynamics are poorly known. We describe the long‐term (N = 25 years) changes in trophic niche breadth of a recovering golden eagle population in a Mediterranean landscape (northern Spain) and search for potential correlates with their productivity (i.e., number of fledged eaglets per controlled pair) as a proxy for their breeding performance (N = 290 pair‐years). We identified a total of 3475 prey items from 77 species; rabbits, hares, and red‐legged partridges were the most frequent prey consumed (overall 51%), followed by roe deer (10%), red‐billed chough, red foxes, and woodpigeons, all of them with >5%. Prey diversity in eagles' diet decreased during the study period. Consumption of rabbits and roe deer increased, while that of hares and partridges decreased; no significant trends were observed in the consumption of foxes, choughs, and woodpigeons. Prey diversity and red‐legged partridge consumption were negatively correlated with productivity at the territory level, while rabbits, corvids, and pigeons showed a strong positive relationship with productivity. The size of the territory showed the strongest positive relationship with productivity, while roughness was negatively correlated. Rabbits and ungulates showed negative and positive correlations with roughness, respectively, while predator consumption exhibited a negative relationship with the size of the territory. Our findings give insights into the potential trophic mechanisms driving the dynamics of recovering apex predator populations; a reduction in the trophic niche breadth toward specific groups of prey, which could be due to a higher availability and individual specificity toward these prey species, might enhance productivity at the territory level and, ultimately, influence population dynamics facilitating the recovery process. The remarkable increase in the consumption of wild ungulates, predators, and other apex consumers suggests that the current population recovery and reduced trophic niche breadth may facilitate this eagle population to exhibit its apex role and contribute to ecosystem functionality.

Understanding the rules that govern the successions of gut microbiota is prerequisite for testing general ecological theories and sustaining a desirable microbiota. However, the ignorance of microeukaryotes raises the question of whether gut microeukaryotes are assembled according to the same rules as bacteria. We tracked the shrimp gut bacterial and microeukaryotic communities by a longitudinal dense sampling. The successions of both domains were significantly correlated with host age, with relatively stable microeukaryotic communities in adult shrimp. Gut microeukaryotes exhibited significantly higher turnover rate, but fewer transient species, lower proportion of temporal generalists, and narrower habitat niche breadth than bacteria. The γ-diversity partitioning analysis revealed that the successions of gut microbiotas were primarily ascribed to the high dissimilarity as shrimp aged (βIntraTimes), whereas the relative importance of βIntraTimes was significantly higher for microeukaryotes than that for bacteria. Compared with contrasting ecological processes in governing free-living bacteria and microeukaryotes, the ecological patterns were comparable between host-associated gut counterparts. However, the gut microeukaryotes were governed more strongly by deterministic selection relative to nestedness compared with the gut bacteria, which supports the “size-plasticity” hypothesis. Our results highlight the importance of independently interpreting free-living and host-associated meta-communities for a comprehensive understanding of the processes that govern microbial successions.

The geographic ranges of closely related species can vary dramatically, yet we do not fully grasp the mechanisms underlying such variation. The niche breadth hypothesis posits that species that have evolved broad environmental tolerances can achieve larger geographic ranges than species with narrow environmental tolerances. In turn, plasticity and genetic variation in ecologically important traits and adaptation to environmentally variable areas can facilitate the evolution of broad environmental tolerance. We used five pairs of western North American monkeyflowers to experimentally test these ideas by quantifying performance across eight temperature regimes. In four species pairs, species with broader thermal tolerances had larger geographic ranges, supporting the niche breadth hypothesis. As predicted, species with broader thermal tolerances also had more within-population genetic variation in thermal reaction norms and experienced greater thermal variation across their geographic ranges than species with narrow thermal tolerances. Species with narrow thermal tolerance may be particularly vulnerable to changing climatic conditions due to lack of plasticity and insufficient genetic variation to respond to novel selection pressures. Conversely, species experiencing high variation in temperature across their ranges may be buffered against extinction due to climatic changes because they have evolved tolerance to a broad range of temperatures.