A distinct latitudinal gradient of diatom diversity is linked to resource supply

Abstract

Abstract. For over 200 years, scientists have recognized the nearly ubiquitous poleward decline of species richness, but none of the theories explaining its occurrence has been widely accepted. In this continental study of U.S. running waters, I report an exception to this general pattern, i.e., a U-shaped latitudinal distribution of diatom richness (DR), equally high in subtropical and temperate regions. This gradient is linked unequivocally to corresponding trends in basin and stream properties with impact on resource supply. Specifically, DR distribution was related to wetland area, soil composition, and forest cover in the watershed, which affected iron, manganese, and macronutrient fluxes into streams. These results imply that the large-scale biodiversity patterns of freshwater protists, which are seasonal, highly dispersive, and sheltered by their environment from extreme temperature fluctuations, are resource driven in contrast to more advanced, perennial, and terrestrial organisms with biogeography strongly influenced by climate. The finding that wetlands, through iron export, control DR in streams has important environmental implications. It suggests that wetlands loss, already exceeding 52 million hectares in the conterminous United States alone, poses a threat not only to local biota, but also to biodiversity of major stream producers with potentially harmful consequences for the entire ecosystem.

Disentangling the roles of spatial and environmental variables in shaping benthic algal assemblages in rivers of central and northern China

“…Vanormelingen et al (2008b) discovered that genus Eunophora, Veigaludwigia, Stauroneis, and Actinella show restricted biogeographic range. Passy (2010) found a U-shape latitudinal gradient in species richness of benthic diatoms across continuous American streams. These new findings imply that dispersal limitation of algal species, caused by historical events, evolutionary processes, or biological interactions, etc., do influence regional community patterns (Soininen 2007).…”

On the factors affecting distributions of freshwater diatom species in a remote South Atlantic archipelago

“…Elsewhere, many freshwater diatom species show both strongly biogeographically constrained distributions (Kociolek & Spaulding, 2000) as well as possessing clear ecological optima with regard to water quality (e.g. Birks et al, 1990) and resource supplies (Passy, 2010). Here we show that both local environmental and biogeographically related factors contribute significantly to the species composition (cf.…”

“…Global distributions of diatom microalgae are shaped by a variety of criteria including colonization and dispersal (Vyverman et al, 2007), habitat quality (Telford et al, 2006;Passy, 2010), climate (Douglas et al, 2004), and evolution (Mann & Droop, 1996). Rather than being distributed ubiquitously (e.g.…”

Anthropogenic Drivers Shift Diatom Dominance–Diversity Relationships and Transparent Exopolymeric Particles Production in River Ganga:Implication for Natural Cleaning of River Water

“…Withinhabitat diversity (species evenness, concentration of dominance and Shannon-Wiener index) declined with decreasing N : P stoichiometry and water column light penetration indicating that sites situated downstream, despite being nutrient-enriched, were relatively less favourable for most of the species. The abundance and diversity of diatoms vary with nutrient supply along regional 8 and latitudinal 17 gradients, and the strategy to cope with resource availability/stressors has led to the evolution of diverse life forms 18 . Relatively small difference in Shannon-Wiener index and increases in the index Values are mean (n = 27)  ISE.…”