Repeatable patterns in the distribution of freshwater biodiversity indicators across contrasting landscapes

Context: Freshwater biodiversity is declining at unparalleled rates, but fundamental questions remain over how it is distributed at the spatial scales most relevant for conservation management. Objectives: Here, we test the hypothesis that freshwater biodiversity is distributed across standing waterbody types in a pattern that is reproducible across disparate biota and contrasting landscapes, such that conservation efforts can be aligned across landscapes and taxa. Methods: We analysed the richness, composition and distribution of macrophytes, molluscs, beetles and odonates from 199 standing waterbodies (lakes, ponds, ditches and canals) nested within UK landscapes with contrasting dominant land use (agricultural, upland and suburban). Results: We found a common pattern in the distribution of our biodiversity indicators across waterbody types in all landscapes that was largely repeated across biota; lakes consistently had the highest or equal alpha diversity and supported a greater proportion of the sampled species pool in each landscape (mean = 86%) in comparison to ponds (74%). Landscape-specific waterbody types (ditches and canals) also contributed significantly to the regional species pool (69 and 33% respectively). Each waterbody type contributed uniquely to landscape biodiversity and usually species of conservation concern, rather than simply supporting a subset of ubiquitous species found in lakes. Conclusions: Landscape-wide management strategies that encompass multiple habitats and biota should prove advantageous and generalisable. However, our study landscapes suggest that long-term biodiversity conservation should also recognise lakes as a priority for nature recovery, both to minimise further losses and to maintain the largest reservoir of biodiversity.