Macaronesian diversification: Potential isolation of benthic marine protists on seamounts and islands
Evolution, Anthropology
Microbial Ecology and Applied Microbiology
Oceanography
Systematics and Morphology (Zoology)
Final Report Abstract
Heterotrophic protists are the most diverse eukaryotes in the world’s oceans and are important for the matter flux in the marine realm. However, our knowledge on the processes leading to this enormous diversity is very limited. The aim of our project was to further resolve the question how this diversity evolved in the oceans. For larger organisms, there is a solid basis of research available especially for littoral and sublittoral regions, where the theory of island biogeography has been accepted, which states that islands and seamounts play an important role for the evolution of species due to their isolated positions. In this project, we wanted to investigate if this theory also applies to protists. We hypothesized that Macaronesian islands show endemism of certain protist species due to their isolated position and the biogeographical separation of littoral/bathyal and deep-sea benthic protist communities. To test this hypothesis, we took sediment samples along transects of 250, 500, 750 and 1000m depths at two Macaronesian islands, Madeira and Porto Santo, and used an integrative approach to investigate the diversity and distribution of benthic protist communities along the transects. We combined an environmental sequencing approach with abundance estimations and a cultivation-based approach. Furthermore, we combined the results from the Macaronesian islands with results from the Azores, where we used a similar approach. This combined dataset on island slope communities was then compared to our dataset on protists in different deep-sea basins worldwide. All approaches showed that distribution patterns of protist communities are dependent on depth and that the two Macaronesian islands, separated by deep-sea regions, seem to harbour unique protist communities, supporting our hypothesis that many marine protist species are limited in their distribution and restricted to certain depth due to missing adaptations to deep-sea conditions. The same pattern was observed at the Azores islands. Comparing the communities of the Madeira islands with communities from the Azores, communities differ more strongly between island groups than among islands of one group. Furthermore, our analyses showed a strong separation between communities from island slopes and deep-sea plains. These findings support our hypothesis that benthic protist communities on different islands are separated by surrounding deep-sea regions. Speciation processes seem to be supported by the biogeographical isolation of species on island slopes, leading to unique protist communities. Within this project, we added an important new dataset for identifying the role of islands and seamounts for the speciation of unicellular protists and we contributed a step for understanding the origin of marine protist diversity. This is an important prerequisite for the future conservation of marine habitats in times of global warming, deep-sea mining and diversity loss.
Publications
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PhD thesis (2022): “Biogeography and its impact on benthic heterotrophic protists – Investigations from the littoral to the deep sea”
Manon Dünn
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Distribution Patterns of Benthic Protist Communities Depending on Depth Revealed by Environmental Sequencing—From the Sublittoral to the Deep Sea. Microorganisms, 11(7), 1664.
Dünn, Manon & Arndt, Hartmut
