The ecological niche is a complex concept encompassing the responses to abiotic conditions and biotic interactions of coexisting individuals and species. These responses determine the survival of individuals and populations, their role in ecosystem functioning, the selection of particular traits and adaptations, and evolutionary processes. Integrating these multiple processes into a conceptual framework involves understanding phenomena occurring at multiple spatial and temporal scales, as well as the interconnections between them. Research on these phenomena is addressed by many disciplines, comprising a diverse mosaic of research lines that hampers synthesis in biodiversity science, and may result in misperceiving the importance of processes across scales. Understanding niche variations requires integrating ecological and evolutionary processes within the spatial and temporal context where they occur. This implies adopting a multidisciplinary approach to explore the reciprocal effects of niche and coexistence at multiple spatial and temporal scales, incorporating research in ecology, evolution and biogeography to identify which phenomena transfer between scales, and how. Over the last years we studied the ecological and evolutionary implications of the interplay between niche and coexistence at different scales through several projects. UNITED and SCENIC developed experimental approaches to study the niche and coexistence of soil mosses, empirical studies on dune plant communities, and macroecological studies on mosses, vascular plants and insects, obtaining a preliminary understanding of how niche-driven responses to abiotic gradients vary across scales, and how they influence the outcome of local interactions –and with it of natural selection. We found that positive interactions may be frequent even under intense competition, and that the sign and intensity of interactions varies along environmental gradients. These insights helped developing theoretical models for local communities, host-symbiont metacommunity dynamics, and trait evolution under variable environmental conditions. In parallel, NiDEvA studied niche variations within Araliaceae, a lineage of flowering plants, at different geographical and evolutionary time scales from regional shallow scales to global deep-time scales. Our findings reveal how the interplay between spatial processes, niche evolution and species interactions led to hybridization with whole-genome duplication and impacted evolutionary processes and current geographical patterns of diversity. The main objective of NICED is to advance further the understanding about the consequences of niche-mediated responses to abiotic conditions and biotic interactions along geographic gradients for the coexistence of species in communities, and the evolution of their niches through time. This overarching question will be addressed through a series of empirical, experimental and modelling approaches to ecological, evolutionary, and biogeographical research, carried out by two complementary subprojects, focused on the effects of niche and interactions on, respectively, communities and species distributions (Subproject 1), and selection and macroevolutionary processes (Subproject 2). The insights coming from both subprojects will be incorporated into theoretical models.
NICED Subproject 1 will combine ecological and biogeographical perspectives to study the variations in the intensity and sign (positive or negative) of ecological interactions along large-scale environmental gradients, and will incorporate the insights coming from both subprojects and former projects into theoretical models.
First, we will study the changes in the effects of coexistence on niche-based responses along geographical gradients. We will do this through two specific objectives. On the one hand, we will characterize geographical shifts in local species interactions in dune communities of the Iberian Atlantic Coast. We will use data from former projects and conduct new surveys of dune vegetation communities, to study the interplay between local and large-scale environmental gradients and species interactions in the coexistence of shrub species including spatial variations in host-symbiont associations through the study of shifts in the ecological role and degree of heterotrophy of the hemiparasite Osyris lanceolata. On the other hand, we will assess the reciprocal effects of niche and coexistence on the geographic distributions of species. We will use data from biodiversity databases to estimate the degree of spatial association (positive or negative) between pairs of species, and relate it with niche and trait similarity, and species’ evolutionary relatedness through novel macroecological analyses. These latter analyses were developed during SCENIC, but their estimates are critically affected by the taxonomic and spatial uncertainty caused by the limited coverage of biodiversity databases. This implies that generalizing their application to massive biodiversity databases requires incorporating an explicit treatment of data-driven uncertainty. Therefore, another objective of this subproject will be to design analytical tools to account for data-driven uncertainty in macroecological estimates of niche and coexistence, which we will achieve by implementing data cleaning protocols and maps of biogeographical ignorance (i.e. spatial accounts of uncertainty) into R packages and ModestR, an already established software suite for analysing biodiversity big data. These three objectives will advance further our understanding of the whys and wherefores of the spatial variations in the interplay between the species’ niche-based responses and their coexistence from a biogeographical perspective.
Second, NICED Subproject 1 will integrate community, metacommunity and quantitative genetics models developed during former projects, and incorporate the spatial variation of different types of interactions following the empirical results from both subprojects, with the end objective of providing realistic models of the ecological and evolutionary responses to large- and small-scale abiotic gradients under coexistence in local communities. This will advance in the theoretical synthesis about the varying effects of niche-based responses and coexistence across scales. Finally, this subproject will also be in charge of coordinating the data management, access to infrastructures, and outreach and dissemination of both NICED subprojects.