Lake and catchment‐scale determinants of aquatic vegetation across almost 1,000 lakes and the contrasts between lake types

Abstract

Aim The factors controlling macrophyte (aquatic plant) composition are complex, recent research having shown that the well‐studied effects of lake environmental factors (the so‐called “environmental filter”) can be constrained by hydrological and landscape factors. We investigated the factors determining macrophyte composition in lakes over water body and catchment scales and the transferability of this pattern across lake types. Location Almost 1,000 lakes distributed across Britain. Taxon Lake macrophytes. Methods Lakes were partitioned into five types based on subdivision of alkalinity and elevation gradients. Data from botanical surveys were used to compare the spatial turnover and nestedness components of beta diversity between lake types. The relative importance of lake environment (based on local physicochemical data), hydrology (e.g. lake and stream density), landscape (e.g. fragmentation indices, land cover) and spatial autocorrelation in explaining variation in macrophyte composition were derived from variance partitioning. Results Species composition showed strong spatial structuring, suggestive of overland dispersal, enhanced by spatially correlated abiotic factors such as alkalinity and elevation. Catchment‐scale factors (e.g. land use, connectivity) promoted the establishment of different communities (more or less diverse, or differing in composition) but were of secondary importance. Turnover in composition between upland lakes was lower than in other lake types, reflecting a more specialist flora and increased potential for propagule exchange due to spatial aggregation and higher hydrological connectivity. Main conclusions Vegetation composition in lakes is more spatially structured than previously appreciated, consistent with the importance of dispersal limitation, but this does not apply evenly to all lakes, being most acute in lowland high alkalinity lakes. Thus, spatially structured abiotic factors, such as alkalinity, influence macrophyte composition most (suggestive of niche filtering) in high alkalinity lakes where human impacts tend to be greatest, although nestedness was also lowest in such lakes. By contrast, hydrological connectivity has a proportionally stronger structuring role in upland lakes.

Temporal development of biodiversity of macrophytes in newly established lakes

“…High densities of resident and migratory water birds are present along the west coast and can efficiently disperse macrophyte propagules, which can aid the development of high species richness (Hansen, 2009;Petersen et al, 2010). Error bars are the standard error of the mean (Alahuhta & Heino, 2013;Sun et al, 2019). Below: average vegetation cover in the analysed age groups.…”

“…Below: average vegetation cover in the analysed age groups. Error bars are the standard error of the mean (Alahuhta & Heino, 2013;Sun et al, 2019). In a restoration context, when the aim is to create new lakes of high biodiversity, the corollary would be to establish new lakes in landscapes with existing species-rich localities nearby.…”

“…Recent studies using large datasets have shown that well-known environmental influences (e.g. alkalinity and nutrients, Vestergaard & Sand-Jensen, 2000a) can be constrained by hydrological and landscape factors (Alahuhta & Heino, 2013;Sun et al, 2019). The research interest in macrophytes is well motivated as they are important for environmental quality, food web composition, and biodiversity in natural lakes (Jeppesen et al, 1998;Madsen & Sand-Jensen, 1991).…”

Influence of historical landscape on aquatic plant diversity

“…Contemporary land use in the surrounding landscape is however well recognized to pattern macrophyte species assemblages (Cheruvelil & Soranno, 2008;Joniak, Kuczyńska-Kippen, & Gąbka, 2017;Sun, Hunter, Tyler, & Willby, 2019) but its effect varies with the considered spatial extent (Akasaka, Takamura, Mitsuhashi, & Kadono, 2010;Pedersen, Andersen, Ikejima, Hossain, & Andersen, 2006).…”

Global-scale drivers of ploidy state in aquatic macrophytes

“…As a group, aquatic macrophytes are generally considered to occupy a "stressful environment", in terms of factors that may reduce their productivity, in all or most of the habitats where they are found (Grime, 1979;Santamaría, 2002). These factors include light, nutrient and carbon availability, temperature regime, sediment conditions, and alkalinity (e.g., Bornette & Puijalon, 2011;Iversen et al, 2019;Sun et al, 2019). However, the intensity of environmental stress and disturbance tolerated by individual species, and sometimes among individual populations of a given species across its range varies considerably.…”