Garcia-Giron, J. | bioRxiv Science

bioRxiv2026

Testing the waters of macrophyte biodiversity with multiscale spatial analysis of public lake monitoring data

Freshwater monitoring programmes like the European Unions Water Framework Directive (WFD) provide a wealth of data on European lake status, including water quality and macrophytes (aquatic plants) as critical habitat features that support health of humans and wildlife. Easier WFD data access can enable external management and research to better safeguard human and natural freshwater use. We demonstrate a replicable workflow to easily download and process multi-year (2007-2024) observations of lake macrophytes (425 sites) and complementary water quality variables (202 sites) from Swedish WFD data. Then, we illustrate the value of improved data access to address ecological questions that drive conservation, investigating how spatial scales influence macrophyte richness and associated water quality relationships using a spatial random intercept model. Decomposing the spatial intercept links small scales (<10 km) to site-level gradients and large scales (>100 km) to biogeographical drivers. Stochastic and environmentally-structured processes coexisted at intermediate scales (10-100 km). Adding water quality rarely improved overall predictive performance of macrophyte diversity models but consistently influences the role of different spatial scales. Water quality variables showed consistent spatially structured variation at intermediate scales and unique spatial patterns in tandem, overlapping with large-scale biogeographical influences. Altogether, we show context-dependencies for spatial model interpretation and provide guidance in accounting for spatial confounding to improve inferential and predictive performance. Our workflow and results show a clear way forward for accessing high-quality macrophyte and water quality data sets and their utility for addressing ecological questions that guide macrophyte protection under the WFD. HighlightsO_LIyears Swedish of macrophyte and water quality monitoring data were extracted. C_LIO_LIrichness showed scale-specific patterns linked to geographic gradients. C_LIO_LIbest predictive models for richness had no water quality at all. C_LIO_LIoverlap in their spatial scales and must be carefully separated. C_LIO_LIpen access data and multiscale analysis can apply to many ecological questions. C_LI

ecology↗

bioRxiv2021

Patterns and mechanisms underlying ecoregion delineation in North American freshwater plants

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSAimC_ST_ABSBiogeographical regionalisations are actively studied in different ecosystems, because they increase our understanding on fundamental broad{square}scale patterns and can help us in the establishment of conservation areas. Thus, we studied how well existing freshwater ecoregions describe geographical delineation for inland water plants and which ecogeographical gradients explain them. LocationNorth America, excluding Mexico and remote islands. TaxonFreshwater vascular plants of all taxa and different functional groups. MethodsUsing newly available fine-grained data on freshwater plant distributions, we calculated internal homogeneity and cross-boundary heterogeneity among neighbouring ecoregions. We further integrated measures of community dissimilarity to assess whether the degree of within-ecoregion homogeneity and distinctness are driven by their relationships to species replacements and richness differences, and explored how a complex suite of ecogeographical mechanisms and plant life forms affect ecoregion delineation using spatially explicit regression routines. ResultsWe found a clear geographical patterning of ecoregion robustness for North American freshwater plants, with their communities being more internally homogeneous and more similar to one another in polar and subtropical inland waters. Surprisingly, the degree of internal homogeneity and ecoregion distinctness were almost equally driven by species replacements and richness differences. Considering different life forms, ecoregion delineation performed best for emergent and floating-leaved plants. Finally, within-ecoregion homogeneity and distinctness were best explained by annual mean temperature and terrain ruggedness, respectively, with mean water alkalinity, ecoregion area and Late Quaternary Ice Age legacies having supplementary effects. Main conclusionsOur findings emphasise that geographical regionalisations founded on a particular organismal group are not applicable for all taxa. Our study is a promising starting point for further investigations of geographical delineations for different freshwater taxa. These updated regionalisations can then be used for conserving different biotas in freshwaters, which are currently among the most threatened ecosystems in the world. SO_SCPLOWTATEMENTC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWOFC_SCPLOWO_SCPCAP C_SCPCAPO_SCPLOWSIGNIFICANCEC_SCPLOWIn biogeographical regionalisation biota is categorized to meaningful geographical units, such as ecoregions. However, ecoregions delineated for a particular group of organisms may not be applicable to another assemblages. We studied how ecoregions founded on fish are suitable for freshwater plants across North America. Our findings suggest that these ecoregions did not show consistent robustness for freshwater plants in North America. This study is a promising starting point for further investigations of geographical delineations for different freshwater taxa, having also value in conservation planning and management.

ecology↗