Broad-scale studies of species distributions and diversity have contributed to the emergence of general macroecological rules. These rules are typically founded on research using well-known terrestrial taxa as models and it is thus uncertain whether aquatic macrophytes follow these macroecological rules. Our purpose is to draw together available information from broad-scale research on aquatic macrophytes growing in lakes, ponds, wetlands, rivers and streams. We summarize how different macroecological rules fit the patterns shown by freshwater plants at various spatial scales. Finally, we outline future actions which should be taken to advance macroecological research on freshwater plants. Our review suggested that some macroecological patterns are relatively well-evidenced for aquatic macrophytes, whereas little information exists for others. We found, for example, that the species richness-latitude relationship follows a unimodal pattern, and species turnover prevails over species nestedness, whereas higher nestedness-related richness differences are found in low beta diversity regions. Contrary to terrestrial plants, climate or history seem not to be dominant determinants explaining these broad-scale patterns; instead local explanatory variables (e.g., water quality, such as alkalinity and nutrients, and hydromorphology) are often important for freshwater plants. We identified several knowledge gaps related, for example, to a smaller number of studies in lotic habitats, compared with lentic habitats, lack of spatiallyadequate aquatic plant studies, deficiency of comprehensive species traits databases for aquatic macrophytes, and absence of a true phylogeny comprising most freshwater plant lineages. We hope this review will encourage the undertaking of additional macroecological investigations on freshwater plants across broad spatial and temporal scales.

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Geodiversity is an emerging, multi-faceted concept in Earth and environmental sciences. Knowledge on geo-diversity is crucial for understanding functions of natural systems and in guiding sustainable development. Despite the critical nature of geodiversity information, data acquisition and analytical methods have lagged behind the conceptual developments in biosciences. Thus, we propose that geodiversity research could adopt the framework of alpha, beta and gamma concepts widely used in biodiversity research. Especially, geodiversity research would benefit from widening its scope from the evaluation of individual sites towards more holistic geodiversity assessments, where between-site geodiversity is also considered. In this article, we explore the alpha, beta and gamma concepts and how they can be applied in a geodiversity framework. In addition, we scrutinize the statistical methodology related to alpha, beta and gamma geodiversity evaluations, with a special focus on distance metrics for measuring beta geodiversity. As an overview of the process, and to give practical guidelines for the application of the proposed methodology, we present a case study from a UNESCO Global Geopark area. Thus, this study not only develops the geodiversity concept, but also paves the way for simultaneous understanding of both geodiversity and biodiversity within a unified conceptual approach.

Aim Conserving freshwater biodiversity in a rapidly changing world requires updated planning schemes and research efforts. Geodiversity – the diversity of Earth surface forms, materials and processes – and biodiversity are interlinked at a fundamental level. This relationship is being considered in a growing number of studies, yet research from freshwater environments is scarce. We used geodiversity (rock‐type, soil‐type and geomorphological richness), local and climatic variables to explore whether geodiversity can be used as a surrogate for aquatic plant species richness in lakes and rivers. Location Finland. Taxon Aquatic plants. Methods We compared geodiversity variables (measured within 1‐km2 grid cells) to well‐studied local (e.g. area, alkalinity) and climate (e.g. growing degree‐days) variables, and examined the patterns between habitat types (lakes and rivers) and among all taxa and major functional groups (helophytes and hydrophytes). We modelled lake (n = 145) and river (n = 146) plant species richness with generalized linear models, and further partitioned variation to measure the independent and shared contributions of the geodiversity, climate and local environmental variable groups. As a complementary analysis, and to identify single important variables explaining variation in aquatic plant species richness, we utilized boosted regression trees. Results We found a positive relationship between aquatic plant species richness and catchment geodiversity variation with recurring patterns across two different freshwater habitat types and two aquatic plant functional groups. Higher variation in geodiversity (measured at landscape scale) supported higher freshwater biodiversity (measured at the local scale) of lakes and rivers. Main conclusions Geodiversity can be a useful addition to biodiversity modelling, and it should be considered in conservation schemes and monitoring efforts, further supporting the principle of conserving nature's stage. Yet, differences between habitats and functional groups suggest that more habitat‐specific approaches and multiple biodiversity measures should be considered. Our study is an important signpost guiding further studies on the biodiversity–geodiversity relationship in freshwater ecosystems.

The non-living and the living nature are inherently connected. Geodiversity, that consist of the variation in geology, soils, topography, geomorphology and hydrology, is seen as the foundation and stage for biodiversity. Underlying theory suggests that the increasing variation in the abiotic foundation creates and maintains available niche space for different organisms to thrive, resulting in higher biodiversity. Emerging scientific observations support this premise, indicating a positive influence of geodiversity on biodiversity across different environments, regions, and spatial scales. Inclusion of geodiversity into biodiversity research and conservation has therefore capacity to improve our understanding of biodiversity patterns and dynamics. Current challenges that need to be overcome in this relatively new field of science are related to defining and measuring geodiversity and gaining still more empirical evidence on the link between geodiversity and biodiversity. Despite these challenges, connecting these two concepts and embracing the interdisciplinary cooperation, has great potential in advancing our understanding of diversity of nature and integrating geodiversity in conservation assessments across scales.

The biodiversity of aquatic ecosystems is under threat and there is an urgent need to quantify the various facets of biodiversity to assess the conservation value of freshwater ecosystems. The effects of taxonomic relatedness have so far not been taken into account in biodiversity assessments of lake macrophytes. We therefore tested the response of species richness and average taxonomic distinctness (AvTD) of aquatic macrophytes along environmental gradients using linear regression models and Bayesian Information Criterion variable selection method. We selected data from four regions, each with 50–60 lakes, situated in northern Europe (Finland and Sweden) and northern America (Minnesota and Wisconsin). We separately studied all macrophyte species, hydrophytes and helophytes. Species richness and AvTD of aquatic macrophytes were generally negatively related in all regions, although it was not statistically significant. Both biodiversity measures responded to environmental gradients to various degrees among the studied macrophyte groups and regions. Species richness was best explained by alkalinity and lake area in Finland, by elevation, annual mean temperature and total phosphorus in Minnesota, and by alkalinity in Wisconsin. AvTD was best explained by alkalinity, annual mean temperature and total phosphorus in Finland and by alkalinity in Wisconsin. Very weak relationships were found in Sweden. Our findings strongly suggest that complementary indices are needed to indicate more comprehensively the effects of environmental conditions on freshwater biodiversity. Species richness was found to be a better measure than AvTD to account for conservation value in freshwaters. However, further research is required to evaluate the usefulness of AvTD to indicate conservation value (e.g. randomisation tests), because alternative measures are clearly needed for those freshwater taxa lacking complete information on true phylogenetic diversity.

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