The Evolutionary History and Phylogeny of the Lithodinae (Decapoda: Anomura: Lithodidae)

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

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2010

Author dc:creator

• Snow, Sarah Marie