Patterns of diversity in microscopic organisms are hypothesised to differ from macroscopic ones, as small size, desiccation tolerance, and dispersal capability should allow micro-organisms to achieve global distributions.
We test the predictions of this ubiquity hypothesis at all levels of biodiversity (alpha-, beta- and gamma-diversity) using morphological, ecological and molecular taxonomy approaches. The models we use are both prokaryotes and microscopic eukaryotes such as rotifers.
The questions we address surround the so-called 'everything is everywhere' hypothesis, trying to evaluate the processes that generate spatial patterns of diversity and biogeography in organisms that can potentially be cosmopolitan. We thus ask whether microorganisms are really cosmopolitan in their distribution; what the biological properties that allow such potential distribution are; what processes would limit their distribution; whether microorganisms are intrinsically different from macroscopic organisms; what microorganisms can tell us about the generalities of biogeography; and whether they could be used for experimental biogeography.
Overall, our results suggest that geographic isolation may act in shaping diversity also in microscopic organisms, even if the spatial scale of the effect is wider than for larger organisms.
The results of this topic are summarised in an edited book on the biogeography of microscopic organisms (click on the book to access it).