The concept of the ecological niche is fundamental to understanding species distributions but it often overlooks the critical role of demography in shaping said distributions. Conversely, demographic theory has traditionally neglected how vital rates vary across environments, limiting our understanding of population dynamics across species’ ranges. Over 50 years ago, Maguire proposed conceptualising the ecological niche as composed of multiple “demographic niches” corresponding to separate vital rates such as survival, development, and reproduction. Despite its potential for ecological research, Maguire’s perspective never really took off. Here, we introduce the “demographic niche concept” (DNC), a contemporary evolution of Maguire’s perspective, integrating recent advances in niche theory and demography to formalise the DNC. We first outline the theoretical foundations of the DNC, focusing on vital rate variation along environmental gradients and its role in shaping ecological niches. We then formalise the definition of the DNC, explore how demographic niches and their boundaries are determined, and introduce a framework for applying the DNC in environmental and geographic spaces. Importantly, we present the DNC as a tool for conservation planning by improving our ability to identify critical areas where specific demographic processes are vital for species persistence or absent under global change. Throughout this review, we also explore methods for modelling and integrating demographic niches and discuss their relevance for addressing global challenges such as climate change. By integrating the ecological niche with demographic theory, we propose testable hypotheses on how and why vital rates vary within niche space, the current frontier of the DNC. Finally, we identify key knowledge gaps and suggest research directions to address these gaps. By advancing the conceptual and methodological tools of the DNC, this review establishes a foundation for future empirical research and applications, offering new directions for ecological theory and conservation amidst a changing world.

The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils at 195 plots across the Tibet plateau, with distances among plots ranging from 20 m to 1,550 km. Taxonomic composition of bacterial community was characterized by 16S amplicon sequencing, and functional community composition by qPCR targeting 9 functional groups involved in N dynamics. Twelve climatic and soil characteristics were also measured. Both taxonomic and functional dissimilarities were more related to environmental dissimilarity than geographic distance. Taxonomic dissimilarity was mostly explained by soil pH and organic matter, while functional dissimilarity was mostly linked to moisture, temperature and N, P and C availabilities. The roles of environmental filtering and dispersal were, however, scale-dependent and varied between taxonomic and functional dissimilarities, with distance affecting taxonomic dissimilarity over short distances (<~300 km) and functional dissimilarity over long distances (>~600 km). The importance of different environmental predictors varied across scales more for functional than taxonomic dissimilarity. Our results demonstrate how biodiversity dimension (taxonomic versus functional) and spatial scale strongly influence the conclusions derived of bacterial biogeography.

Soil microbes play a key role in shaping terrestrial ecosystems. It is therefore essential to understand what drives their distributions. While multivariate analyses have been used to characterise microbial communities and drivers of their spatial patterns, few studies focused on modelling the distribution of Operational Taxonomic Units (OTUs). Here, we evaluate the potential of species distribution models (SDMs), to predict the presence-absence and relative abundance distribution of bacteria, archaea, fungi and protist OTUs from the Swiss Alps. Advanced automated selection of abiotic covariates was used to circumvent the lack of knowledge on the ecology of each OTU. ‘Presence-absence’ SDMs were successfully applied to most OTUs, yielding better predictions than null models. ‘Relative-abundance’ SDMs were less successful, yet, they were able to correctly rank sites according to their relative abundance values. Archaea and bacteria SDMs displayed better predictive power than fungi and protist ones, indicating a closer link of the latter with the abiotic covariates used. Microorganism distributions were mostly related to edaphic covariates. In particular, pH was the most selected covariate across models. The study shows the potential of using SDM frameworks to predict the distribution of OTUs obtained from environmental DNA (eDNA) data. It underscores the importance of edaphic covariates and the need for further development of precise edaphic mapping and scenario modelling to enhance prediction of microorganism distributions in the future.

The processes governing soil bacteria biogeography are still not fully understood. It remains unknown how the importance of environmental filtering and dispersal differs between bacterial taxonomic and functional biogeography, and whether their importance is scale-dependent. We sampled soils at 195 plots across the Tibet plateau, with distances among plots ranging from 20 m to 1 550 km. Taxonomic composition of bacterial community was characterized by 16S amplicon sequencing, and functional community composition by qPCR targeting 9 functional groups involved in N dynamics. Twelve climatic and soil characteristics were also measured. Both taxonomic and functional dissimilarities were more related to environmental dissimilarity than geographic distance. Taxonomic dissimilarity was mostly explained by soil pH and organic matter, while functional dissimilarity was mostly linked to moisture, temperature and N, P and C availabilities. The roles of environmental filtering and dispersal were, however, scale-dependent and varied between taxonomic and functional dissimilarities, with distance affecting taxonomic dissimilarity over short distances (<~300 km) and functional dissimilarity over long distances (>~600 km). The importance of different environmental predictors varied across scales more for functional than taxonomic dissimilarity. Our results demonstrate how biodiversity dimension (taxonomic versus functional) and spatial scale strongly influence the conclusions derived from bacterial biogeography studies.

Biotic interactions are key to understanding the ecology of species and communities. As such, integrating biotic interactions into ecological niche modelling methods has been a central topic of research for the last decade. Yet, the role of biotic interactions remains overlooked. Mutualistic systems constitute perfect study cases for analysing the effect of biotic interactions on species niches and communities’ composition. Using the clownfish-sea anemone interaction, we integrate mutualistic interactions into a niche quantification framework to analyse the effect of biotic interactions in the estimation of species niches; and competition patterns among clownfish communities. Our results show that ignoring biotic interactions can strongly affect species ecological niche estimations. More importantly, sea anemones seem to mediate competition among clownfishes, structure communities and allow coexistence in competitive environments. These findings strongly support the importance of biotic interactions in shaping communities. Future studies could use the proposed analytical framework, which could also serve multiple conservation purposes.

Climate change and other global change drivers threaten plant diversity in mountains worldwide. A widely documented response to such environmental modifications is for plant species to change their elevational ranges. Range shifts are often idiosyncratic and difficult to generalize, partly due to variation in sampling methods. There is thus a need for a standardized monitoring strategy that can be applied across mountain regions to assess distribution changes and community turnover of native and non-native plant species over space and time. Here, we present a conceptually intuitive and standardized protocol developed by the Mountain Invasion Research Network (MIREN) to systematically quantify global patterns of native and non-native species distributions along elevation gradients and shifts arising from interactive effects of climate change and human disturbance. Usually repeated every five years, surveys consist of 20 sample sites located at equal elevation increments along three replicate roads per sampling region. At each site, three plots extend from the side of a mountain road into surrounding natural vegetation. The protocol has been successfully used in 18 regions worldwide from 2007 to present. Analyses of one point in time already generated some salient results, and revealed region-specific elevational patterns of native plant species richness, but a globally consistent elevational decline in non-native species richness. Non-native plants were also more abundant directly adjacent to road edges, suggesting that disturbed roadsides serve as a vector for invasions into mountains. From the upcoming analyses of time series even more exciting results especially about range shifts can be expected. Implementing the protocol in more mountain regions globally would help to generate a more complete picture of how global change alters species distributions. This would inform conservation policy in mountain ecosystems, where some conservation policies remain poorly implemented.

Underpinnings of the distribution of allopolyploid species (hybrids with duplicated genome) along spatial and ecological gradients are elusive. As allopolyploid speciation combines the range of genetic and ecological characteristics of divergent diploids, allopolyploids initially show their additivity and are predicted to evolve differentiated ecological niches to establish in face of their competition. Here, we use four diploid wild wheats that differentially combined into four independent allopolyploid species to test for such additivity and assess the impact of ecological constraints on species ranges. Divergent genetic variation from diploids being fixed in heterozygote allopolyploids supports their genetic additivity. Spatial integration of comparative phylogeography and modeling of climatic niches supports ecological additivity of locally adapted diploid progenitors into allopolyploid species which subsequently colonized wide ranges. Allopolyploids fill suitable range to a larger extent than diploids and conservative evolution following the combination of divergent species appears to support their expansion under environmental changes.