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When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON FACULTY OF NATURAL AND ENVIRONMENTAL SCIENCES School of Ocean & Earth Sciences Satellite to Seafloor - The Global Biogeography of the Elasipodid Holothurians by Elizabeth Jane Ross Thesis for the degree of Doctor of Philosophy September 2012 1 2 UNIVERSITY OF SOUTHAMPTON FACULTY OF ENGINEERING, SCIENCE & MATHEMATICS SCHOOL OF OCEAN & EARTH SCIENCES Doctor of Philosophy ABSTRACT Satellite to Seafloor - The Global Biogeography of the Elasipodid Holothurians Elizabeth Jane Ross Knowledge of the environmental factors driving species distributions in the deep-sea is essential for a better understanding of the biogeography of the abyssal benthos. Differences in the niches of elasipodid holothurians appear to exist at the level of species, genera and family. This study analysed the global distributions of elasipodid holothurians from records collected from online Natural History Collection databases, cruise reports and published literature. A comparison of the distribution of four families of elasipodid holothurians, in relation to seven abiotic environmental factors found the families Psychropotidae and Elpidiidae to have the most different environmental distributions. POC flux, intra- annual seasonality and inter-annual variability in POC flux were the best explanatory factors for differences between the families. The Elpidiidae were generally found in areas with greater temporal variability. The potential for biogeographic schemes based upon the ecology of the upper ocean to inform management decisions for the deep sea was also investigated. Results suggest that Longhurst’s ‘case models’ are more closely linked to the distribution of species and genera than Longhurst’s biomes. Results also confirmed that provinces from the same ocean and latitude were more similar in terms of species composition, but that historical factors were equally capable of explaining the observed patterns and must be taken into account. Population genetic studies of two species of Elasipodida; Psychropotes longicauda and Oneirophanta mutabilis were conducted using CO1 and 16S molecular markers. Multiple sympatric lineages were found in the Indian, Pacific and Atlantic Oceans in both species. Differences between sympatric lineages were greater than geographic differences within lineages. The potential for speciation in the Antarctic or Southern Ocean before multiple northwards dispersal events is considered the most plausible explanation for the observed patterns. Oceanic gyres therefore do not appear to be barriers to dispersal in these species. The distributions of the elasipodid holothurians are therefore thought to be controlled by a combination of life-history, dispersal ability, temporal and quantitative variations in food supply and competitive interactions as well as historical processes relating to centres of origin for particular genera. 3 4 ACADEMIC THESIS: DECLARATION OF AUTHORSHIP ........................... 9 ACKNOWLEDGEMENTS ............................................................................... 11 CHAPTER 1. INTRODUCTION ...................................................................... 13 1.1 An introduction to the field of biogeography ....................................................................... 13 1.1.1 What is biogeography? .......................................................................................................... 13 1.1.2 Historical vs. ecological biogeography .................................................................................. 13 1.1.3 Vicariance vs. dispersal biogeography .................................................................................. 16 1.1.4 A brief history of marine biogeography and our current state of knowledge ...................... 17 1.2 Recent developments in biogeographical methods ............................................................ 20 1.2.1 Computerisation of natural history collections and the development of distributed networks .......................................................................................................................................... 20 1.2.2 Remotely sensed data ............................................................................................................. 21 1.2.3 Macroecology ......................................................................................................................... 22 1.2.4 Phylogeography and population genetics ............................................................................. 25 1.3 Biogeography of the deep sea soft sediment fauna ............................................................. 26 1.3.1 A brief overview of deep-sea soft sediment zoogeography and biogeography .................... 26 1.3.2 The deep-sea environment ..................................................................................................... 31 1.3.3 POC flux to the deep-sea floor; Spatial and temporal variations in quantity and quality ... 36 1.3.4 POC flux to the deep-sea floor; effects on the benthos ........................................................... 44 1.3.5 Species diversity in the deep-sea: historical perspectives to modern day estimates ............ 47 1.4 The elasipodid holothurians ................................................................................................... 51 1.4.1 Historical significance ............................................................................................................ 51 1.4.2 Ecological relevance ............................................................................................................... 52 1.4.3 Evolutionary context .............................................................................................................. 55 1.5 Aims and hypothesis ................................................................................................................. 60 CHAPTER 2. MAPPING METHODS ............................................................... 61 2.1 The creation of GIS layers of biological and environmental data ..................................... 61 2.1.1 Mapping the distribution of elasipodid holothurians ........................................................... 61 2.1.2 Mapping environmental data ................................................................................................ 65 2.2 Differences in the environmental distribution of four families of Elasipodida ............. 75 2.2.1 Environmental data extraction from holothurian collection sites ....................................... 75 2.2.2 Statistical analyses ................................................................................................................. 75 2.3 Biogeochemical zonation in the deep sea ............................................................................. 78 2.3.1 Mapping and data layout ....................................................................................................... 78 2.3.2 Statistical analyses ................................................................................................................. 78 5 CHAPTER 3. DIFFERENCES IN THE ENVIRONMENTAL DISTRIBUTIONS OF FOUR FAMILIES OF ELASIPODID HOLOTHURIAN; A GLOBAL AND OCEAN- SCALE ANALYSIS .......................................................................................... 81 3.1 Introduction ................................................................................................................................ 81 3.1.1 Niche theory and resource partitioning in deep-sea echinoderms ....................................... 81 3.1.2 Potential mechanisms for resource partitioning among the Elasipodida in a seemingly homogenous environment. .............................................................................................................. 82 3.1.3 Resource partitioning and reproduction in the elasipodid holothurians ............................. 86 3.1.4. Niche conservatism and Hutchinson’s duality; relating the niche to biogeographic space 90 3.2 Results .......................................................................................................................................... 92 3.2.1 A brief overview of the geographical and vertical distributions of the four families of the elasipodid holothurians ................................................................................................................... 92 3.2.2 The global environmental distributions of the four families of elasipdodid holothurians ... 95 3.2.3 The Atlantic Ocean ............................................................................................................... 106