Speciation and adaptation in Southern Ocean sea spiders
Marine shelf habitats in the Southern Hemisphere have been drastically impacted by glacial periods especially during the Plio- and Pleistocene. Large parts of the sea floor were at least temporarily covered by grounded ice, thereby reducing habitat availability for benthic organisms. Nowadays, an as...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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2020
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| Online Access: | https://doi.org/10.17185/duepublico/70535 https://nbn-resolving.org/urn:nbn:de:hbz:464-20200306-084000-3 https://duepublico2.uni-due.de/receive/duepublico_mods_00070535 https://duepublico2.uni-due.de/servlets/MCRZipServlet/duepublico_derivate_00070494 |
| Summary: | Marine shelf habitats in the Southern Hemisphere have been drastically impacted by glacial periods especially during the Plio- and Pleistocene. Large parts of the sea floor were at least temporarily covered by grounded ice, thereby reducing habitat availability for benthic organisms. Nowadays, an astonishingly high number especially of endemic species has been reported for this shelf fauna. Many of the species have radiated during the Plio- and Pleistocene. Allopatric speciation in independent and isolated refugia has often been postulated as the driving speciation mechanism, especially in the Antarctic, but also at higher latitudes. However alternative driver for speciation have rarely been considered, and especially ecological speciation in sympatry (e.g. shared refugia) due to adaptive divergence seems to be a promising mechanism to address with morphological and genetic data. Hence, one aim of this thesis is to explore evidence for both speciation scenarios focussing on two sea spider species complexes, namely Pallenopsis patagonica (Hoek, 1881) and Colossendeis megalonyx Hoek, 1881. The first study addresses genetic diversity within the P. patagonica species complex. Previously analysed mitochondrial cytochrome c oxidase subunit I (COI) data of Patagonian and Antarctic specimens was expanded by adding further samples from Patagonia, sub- Antarctica and the Eastern Weddell Sea. Furthermore, sequence data for the nuclear internal transcribed spacer (ITS) were added to obtain more information about the species complex. In fact, a higher number of distinct lineages were detected. Some lineages detected by mitochondrial data were not supported by nuclear data probably due to a lack of resolution (too few substitutions) in the ITS region rather than hybridization and speciation reversal events as reported in an earlier study about the sea spider species complex C. megalonyx. While the first study was based on two single-markers only, in the second study of this thesis an unprecedentedly large genomic data set for ... |
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