The pool rules - metacommunities control diversity in aquatic microbes
Friday seminar by Robert Ptacnik.
Is everything everywhere? Once a clean-cut case, the debate on whether microbes are dispersal limited has turned into a lively debate, and there is accumulating evidence that dispersal does affect diversity of unicellular organisms. However, if dispersal affects microbial diversity – may microbial communities be under-saturated? Does variability in microbial diversity affect ecosystem functions in similar ways as it is known from higher organisms?
Using a large datasets from lakes across Fennoscandia, I show that phytoplankton diversity, measured as morphospecies richness, varies considerably in space. Diversity shows a considerable longitudinal gradient, with lowest diversity in western
Phytoplankton biomass per limiting resource (total phosphorus) gives a measure of resource use efficiency (RUE). I show that RUE increases consistently with diversity. On the contrary, variability in resource use and community composition both are negatively correlated with diversity. While phytoplankton diversity is only poorly linked to local environmental factors, spatial analysis reveals strong spatial autocorrelation. Moreover, regional attributes explain >60 % of the variability seen in phytoplankton diversity. Thus, the data strongly indicate the existence of metacommunities, which promote similar species richness among communities of proximate habitats, irrespective of differences among local environmental factors.
Norwegian Institute for Water Research (NIVA)