Von hohen Breiten in die Tropen: Rolle der Paläobiogeographie in der Biodiversifikation der Bryozoen von Balto-Skandinavien
Zusammenfassung der Projektergebnisse
The project comprises a comprehensive investigation of bryozoan faunas from the Ordovician of Baltoscandia. Localities from two time transects, Darriwilian and Sandbian/Katian, were studied and sampled. Additional material was viewed and studied in museum collections. From the studied material 1,335 thin sections were prepared. The taxonomic study revealed 17 species from the Darriwilian localities and 113 species from the Sandbian/Katian localities. Results of the project show that α-diversity and the γ-diversity increased at all levels in the interval from the Darriwilian to the early Katian, whereas the overall β-diversity (turnover) decreases. The β-diversity increased at the regional level (between localities), but remained low within the localities. Darriwilian communities of Baltoscandia are highly endemic, whereas the Sandbian/Katian communities contain significant proportion of alien taxa. The performed study demonstrates that the diversification of bryozoans in Ordovician was driven by a combination of two factors: a) periodic immigrations which maintained an input of higher taxa (genera); b) speciation of genera on the local level within regions. An oscillation of immigration and vicariance events (input of genomes and their diversification at the local/regional level due to further isolation) provides an important precondition for increase of biodiversity. Bryozoan biodiversification was also positively influenced by global factors as sea level rise and increase in atmospheric oxygen and available nutrients.
