| Περιγραφή Προγράμματος: | Two theories have been proposed characterizing the forces shaping ecological communities and leading to species supersaturation niche theory where diversity is determined by the number of available niches and deterministic interactions between species and the environment, and neutral theory where species are equivalent in their competitive and dispersal abilities, and local and regional diversity are determined by stochastic demographic processes and dispersal limitation. A very prominent group of organisms to study the above mechanisms is phytoplankton, since it plays an important functional role in ecosystems and its assemblages are typically rich in diversity. Despite the accumulating number of studies testing the two theories on microbial communities, similar approaches regarding phytoplankton assemblages remain scarce. Moreover an important issue has emerged recently regarding the dominant mechanism shaping natural communities, referring to the type of diversity being studied. Genetic and phenotypic diversity may lead to contrasting conclusions on which mechanism/theory is responsible for the observed community structure. The main aim of the current proposal is the quantification of the relative role of niche and neutral processes in structuring phytoplankton assemblages. It will be addressed by merging/comparing measures resulting from classical identification techniques in the microscope with those from recently proposed molecular methodologies, namely pyrosequencing and 18S rRNA gene sequencing. Information will be collected (a) from enclosed gulfs in the N. Aegean Sea as local communities interacting through the open sea to form a metacommunity, (b) natural mesocosms (enclosures in interconnected saltwork ponds) along a strong salinity gradient, and (c) laboratory microcosms under different migration rate scenarios. Novel methodological approaches (statistical and dynamic models) will be applied to test the specific question in the marine environment.
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Greek