Global patterns and determinants of lake macrophyte taxonomic, functional and phylogenetic beta diversity

Abstract

Documenting the patterns of biological diversity on Earth has always been a central challenge in macroecology and biogeography. However, for the diverse group of freshwater plants, such research program is still in its infancy. Here, we examined global variation in taxonomic, functional and phylogenetic beta diversity patterns of lake macrophytes using regional data from six continents. A data set of ca. 480 lake macrophyte community observations, together with climatic, geographical and environmental variables, was compiled across 16 regions worldwide. We (a) built the very first phylogeny comprising most freshwater plant lineages; (b) exploited a wide array of functional traits that are important to macrophyte autoecology or that relate to lake ecosystem functioning; (c) assessed if different large-scale beta diversity patterns show a clear latitudinal gradient from the equator to the poles using null models; and (d) employed evolutionary and regression models to first identify the degree to which the studied functional traits show a phylogenetic signal, and then to estimate community-environment relationships at multiple spatial scales. Our results supported the notion that ecological niches evolved independently of phylogeny in macrophyte lineages worldwide. We also showed that taxonomic and phylogenetic beta diversity followed the typical global trend with higher diversity in the tropics. In addition, we were able to confirm that species, multi-trait and lineage compositions were first and foremost structured by climatic conditions at relatively broad spatial scales. Perhaps more importantly, we showed that large-scale processes along latitudinal and elevational gradients have left a strong footprint in the current diversity patterns and community-environment relationships in lake macrophytes. Overall, our results stress the need for an inte-grative approach to macroecology, biogeography and conservation biology, combining multiple diversity facets at different spatial scales.

Elements of lake macrophyte metacommunity structure: Global variation and community‐environment relationships

“…This has been demonstrated in two recent global-scale studies that showed variable patterns in the factors shaping species-based beta diversity (Alahuhta et al 2017) and community composition (Alahuhta et al 2018a). Whatever the case, our study results agree with previous works in which climate and water quality were found to be primarily related to variation in macrophyte community composition at regional scales (Capers et al 2010;García-Girón et al 2019a,b;García-Girón et al 2020). However, these findings should be interpreted with caution due to differences in sample timing between macrophytes and lake-level environmental variables in our study.…”

“…Nevertheless, associating the effects of dispersal with the idealized metacommunity types may be difficult, even if they existed (Meynard et al 2013). Meanwhile, previous works using the same test data set showed that environmental filtering overcame the effects of potential connectivity in explaining local communities across the globe (Alahuhta et al 2018a;García-Girón et al 2020). We thus suggest that environmental differences between sites remain the main structuring force within lake macrophyte metacommunities worldwide, although individual metacommunities may respond differently to major limiting or constraining environmental gradients.…”

Principal Determinants of Aquatic Macrophyte Communities in Least-Impacted Small Shallow Lakes in France

“…The influence of regional, spatial, and environmental drivers can vary according to geographic region [60]. Continental France is subject to highly heterogenous climatic conditions in a very small area (less than 600,000 km 2 ), excluding most of the influence of latitude, which may have strong effects on macrophyte communities [61]. Climate and altitude seem to influence macrophyte community composition and not the richness, e.g., filtering some species that are especially adapted to high elevations, such as Philonotis seriata, or endemic species, such as Caropsis verticillato-inundata in the south-west lowlands.…”

Principal Determinants of Aquatic Macrophyte Communities in Least-Impacted Small Shallow Lakes in France

“…The influence of regional, spatial and environmental drivers can vary according to geographic region [59]. Continental France is subject to highly heterogenous climatic conditions in a very small area (less than 600 000 km²), excluding most of the influence of latitude, which may have strong effects on macrophyte communities [60]. Climate and altitude seem to have a marginal influence on macrophyte community composition, e.g.…”