The ecology and evolution of Antarctic Pycnogonida

• Main Author: Maxwell, Jamie
• Other Authors: Alcock, Louise
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Galway 2024
• Subjects: Antarctic Pycnogonida; Natural Sciences; Zoology; Biogeography; sea spiders; mitogenomes; cryptic species; genetics; Antarctic; New Zealand; Southern Ocean; The Antarctic; Antarc*; Antarctica
• Online Access: https://hdl.handle.net/10379/18184; https://doi.org/10.13025/14704

Pycnogonida (sea spiders) are a class of globally distributed arthropods, that are particularly biodiverse within the Southern Ocean. The number of pycnogonid species and increased levels of endemism in the Southern Ocean form the basis of the hypothesis that Antarctica is the evolutionary centre of origin for extant pycnogonids. Despite a long history of investigation into Antarctic pycnogonids, little is known about their phylogeny, ecology, and biogeography. For example, until recently their phylogeny was based exclusively on morphology and low-resolution single gene barcodes, which was unable to resolve interfamilial relationshipsSimilarly, inferences about their ecology have been based on assumptions, interpretation of morphological characters such as their feeding apparatus, low resolution distribution patterns, and rare in-situ observations. Chapter 2 uses taxonomic keys and literature to identify 5704 sea spiders to the lowest taxonomic rank possible. I identified 81 species, across 15 genera and eight families. All records were uploaded to Global Biodiversity Information Facility (GBIF) which increased the number of stations where pycnogonids have been recorded in the Southern Ocean, southern South America, and New Zealand waters by 11% and I have increased, by 18%, the number of stations above 60 degrees latitude. Any observed epifauna were also documented. Chapter 3 used the newly generated data from chapter 2 combined with publicly available occurrence records to investigate the diversity and connectivity of pycnogonid communities either side of the Antarctic Polar Front, with an emphasis on the role of water depth. I found that at depths shallower than 1000 m, communities north and south of the front were distinct, whereas below this depth geographic structure disintegrated, providing evidence that, for pycnogonids, Antarctica becomes less isolated from other Oceans with depth. Chapter 4 used a subset of the dataset in chapter 3 to investigate whether water mass properties had a role in structuring ...