The anomuran sub-family Lithodinae comprises a great diversity of morphological and ecological forms, whose global radiation has not been specifically addressed since the modern syntheses of plate tectonics, oceanography, species theory and cladistic systematics. The focus of this thesis was to investigate the origin and radiations of the deep-sea Lithodinae as a case study for interchanges between deep and shallow oceans in mobile benthic fauna. Molecular sequences were obtained from six genes (for 47 species belonging to 10 genera of Lithodidae) and different aspects of morphology were examined in order to identify nested monophyletic groups based on shared, derived characteristics. The hypothesis that lineage-specific temperature tolerances influence the distribution of deep- and shallow-water groups was tested by examining habitat alongside phylogeny. Lithodid ancestors are likely to have had a north Pacific, shallow-water distribution and planktotrophic larvae. Some shallow-water populations of Lithodidae are tied to locations north of 30°N because of the restricted thermal tolerance of pelagic larval stages; however, life-history changes allowed the subfamily Lithodinae to expand through the global deep sea, where they are now living at the frontier of their lower temperature threshold in the Southern Ocean. Phylogenies indicate the importance of large-scale dispersals within deep-sea groups, linked to the cold deep-water currents that connect the major oceans. The subfamily Lithodinae includes examples of at least two genera in which diverse morphologies have arisen within the deep ocean in the absence of discernable barriers to gene flow. Adult migration and larval dispersal partially explain the widespread occurrence of the Lithodidae, but this does not indicate that lithodids roam the ocean depths unconstrained by physical or chemical conditions. Climate change throughout the Cenozoic has substantially altered the marine environment and shaped the distribution and radiation of the extant Lithodidae. In the forthcoming years, measurable changes in ocean temperature, ocean currents and benthic habitat will affect the distribution of the lithodids and the communities they live in, as they have in the past.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:525732 |
| Date | January 2010 |
| Creators | Snow, Sarah Marie |
| Publisher | University of Southampton |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://eprints.soton.ac.uk/169039/ |
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