Soil microorganisms behave like macroscopic organisms: patterns in the global distribution of soil euglyphid testate amoebae

Abstract

Aim Patterns of α‐ and β‐diversity of soil protist communities and the factors that shape them remain largely unknown. We undertook a world‐wide survey of forest litter to investigate the patterns of diversity in a group of testate amoebae. We aimed to assess: (1) whether there is a latitudinal gradient in α‐diversity, and (2) whether β‐diversity was correlated solely with environmental factors commonly used in soil biology research or if it was also independently explained by geographical barriers. Location World‐wide. Methods We studied the diversity of Euglyphida, a common group of testate amoebae, in 35 samples of forest litter and moss samples from a global survey, using small subunit rRNA gene sequences. We assessed the relationship between sample α‐diversity and latitude using generalized additive models (GAM). Furthermore, we determined the relationships between community composition and geographical models (distance‐based Moran's Eigenvector Maps – db‐MEM) using Generalized UniFrac distances (GUniFrac). We also investigated the relationship between individual measured soil parameters, WorldClim data and diversity (alpha plus beta) using both raw data and synthetic variables obtained through principal components analysis. Results We recorded 245 phylotypes belonging to 6 out of 7 known Euglyphida families, plus four novel deep clades. Euglyphid α‐diversity was positively correlated with temperature and negatively with latitude and litter C/N ratio. Euglyphida community structure was correlated with the spatial eigenvector Db‐MEM31, independently of all measured environmental variables. Db‐MEM31 corresponds to a natural barrier constituted by the Northern Hemisphere desert belt. Beta diversity was correlated with other environmental variables, such as pH, isothermality and temperature in the coldest month of the year. Main conclusions Soil euglyphid α‐diversity displays a latitudinal gradient, and β‐diversity is not only correlated with climatic and physicochemical parameters but also with geographical barriers. Such patterns of diversity were until recently believed to be characteristic only for macroscopic organisms.

Microbial eukaryote communities exhibit robust biogeographical patterns along a gradient of Patagonian and Antarctic lakes

“…Our results show that microbial eukaryote total richness did not change with latitude (Table ) and did not differ significantly between Patagonian and Antarctic lakes (Table ). This contrasts with the prevailing general view of decreasing richness with latitude (Pianka, ; Gaston and Blackburn, ; Hillebrand, ) also observed in soil protists (Lara et al ., ), although there are a number of exceptions for aquatic (e.g. Crow, ; Passy, ) and soil (Fernández et al ., ) eukaryotic microorganisms.…”

Water–energy balance, past ecological perturbations and evolutionary constraints shape the latitudinal diversity gradient of soil testate amoebae in south‐western South America

“…A PCA (Appendix S2) confirmed water and energy variables as primary predictors of testate amoeba richness in SSA, though it also showed that the observed unimodal response to water and energy availability is not easy to separate from other socalled drivers of diversity such as (plant) productivity. Water and energy are undoubtedly essential for physiological processes in testate amoebae (Sch€ onborn, 1962) and have direct effects on their growth, survival and reproductive success (Laminger, 1978;Laybourn & Whymant, 1980), as well as on their abundance, diversity and distribution at large spatial scales (Wilkinson, 1994;Bates et al, 2013;Lara et al, 2016;present study). This calls for attention, especially when attempting to determine whether the reason behind the observed climate-richness links is physiologically based water-energy balance or trophically based productivity (Hawkins et al, 2003).…”

Geo‐climatic factors drive diatom community distribution in tropical South American freshwaters

“…That is, as traits of a given species determine whether or not they can colonize new habitats, the community structure of an ecosystem is closely related to its spatial configuration. Despite the long‐standing but contested claim that unicellular organisms are only driven by local environmental filters due to large population densities and highly efficient dispersal (Finlay, ), major advances have been made indicating the importance of both niche and dispersal‐assembly theories in explaining the spatial distributions of micro‐organisms in aquatic and terrestrial systems (Barberán & Casamayor, [bacteria]; Viana et al., [microcrustaceans]; Moresco et al., [phytoplankton]; Heino et al., [diatoms]; Lara, Roussel‐Delif, Fournier, Wilkinson, & Mitchell, [testate amoeba]).…”