Spatial scaling of microbial eukaryote diversity

Abstract

Patterns in the spatial distribution of organisms provide important information about mechanisms that regulate the diversity of life and the complexity of ecosystems. Although microorganisms may comprise much of the Earth's biodiversity and have critical roles in biogeochemistry and ecosystem functioning, little is known about their spatial diversification. Here we present quantitative estimates of microbial community turnover at local and regional scales using the largest spatially explicit microbial diversity data set available (> 10(6) sample pairs). Turnover rates were small across large geographical distances, of similar magnitude when measured within distinct habitats, and did not increase going from one vegetation type to another. The taxa-area relationship of these terrestrial microbial eukaryotes was relatively flat (slope z = 0.074) and consistent with those reported in aquatic habitats. This suggests that despite high local diversity, microorganisms may have only moderate regional diversity. We show how turnover patterns can be used to project taxa-area relationships up to whole continents. Taxa dissimilarities across continents and between them would strengthen these projections. Such data do not yet exist, but would be feasible to collect.

Turnover of soil bacterial diversity driven by wide-scale environmental heterogeneity

“…The TAR measures the spatial turnover of community richness and allows the rate of community composition turnover (commonly referred to as z) to be calculated. According to Green et al 9 , z can be equivalently calculated from the increase of community richness with sampled area or from the decay of similarity in the community composition with increasing distance between sampling sites. Here the bacterial community composition of the soil samples was characterized by ARISA and the samples were sorted into OTUs.…”

“…In microorganisms, phylogeographic studies have revealed that the genetic similarity within particular populations decreases with distance, which suggests a significant influence of dispersal limitation, leading to strong endemism 3 , and contradicts the hypothesis of microbial cosmopolitanism 8 . At the community level, biogeographical studies have indicated that diversity turnover is influenced both by geographical distance 9 and environmental heterogeneity (as classified by soil, vegetation and climatic characteristics) 10,11 . However, few in-depth studies have been carried out on the TAR of soil microorganisms, especially for soil bacteria, leading to a lack of concepts concerning the diversification processes.…”

“…TAR was extended to microorganisms less than a decade ago 3,9,13 by focusing on community similarity between sites:…”

“…Nowadays, TAR is commonly used in this form in most microbial biogeographical studies 3,9,[14][15][16] to assess microbial diversification and its potential relative dependency on ''dispersal'' and ''habitat heterogeneity'' (including habitat diversity and landscape configuration) 4 . Nevertheless, the TAR is still highly debated, particularly regarding its form, underlying hypotheses and factors affecting the relationship [17][18][19] .…”

Molecular eco-systems biology: towards an understanding of community function

“…Previous studies have detected variation in species composition in various habitats, both spatially (reviewed, for example, in Refs [35,[63][64][65]) and temporally (for example, Refs [66,67]). Spatio-temporal variation has been linked to variation in environmental conditions [35,68], even to the point at which environmental parameters can be predictive of species composition [55].…”