The evolutionary history and biogeography of South African nudibranch molluscs (Euthyneura: Nudibranchia)
Thesis (MSc)--Stellenbosch University, 2017.
ENGLISH ABSTRACT: South Africa lies at the interface of two opposing oceanographical systems boasting incredibly biodiverse and unique marine environments, however it is estimated that a large amount of the biodiversity still remains undiscovered and undescribed. The SeaKeys collaborative project led by SANBI aims to tackle the paucity of marine biodiversity knowledge in South Africa, and this Masters project functions to update the knowledge on the unique marine taxon Nudibranchia (Euthyneura: Nudipleura) in South Africa. Nudibranchs are a charismatic species and popular subjects for diving photographers and citizen scientists and as a result there are many unpublished records in grey literature, identification guides and online forums which have not yet been incorporated into science. This project therefore worked closely with citizen scientists with excellent knowledge on their local nudibranch fauna and called for the public to contribute their nudibranch observations to iSpotnature and SANBI’s Sea Slug Atlas. Using this approach, distributional information for 382 putative South African species was accumulated and is herein documented with references to published photographs (in literature and online). Nudibranchs make ideal study species to elucidate information not only on the present biodiversity patterns and processes governing them along the South African coastline, but the large distributions of genera and families across the globe allows for the testing of historical biogeographical processes, providing insight into the manner in which the South African coastal marine biodiversity was shaped over evolutionary timescales. Using molecular methods, genetic sequence data of three genes (mtDNA: COI, 16S, nDNA: H3) for146 putative South African morpho-species were amplified. Analyses revealed these to constitute 163 distinct genetic lineages, hereby bringing to light at least 16 cryptic lineage complexes along the coastline and exposing several species that are currently misclassified. Additionally, through the comparisons of sequences of South African morpho-species to their conspecifics that reside in the Northern Atlantic and in the Indo-Pacific, significant (specieslevel) sequence divergence was found for over 40% of species examined in this study, indicating the extent of isolation and endemicity along the entire coastline is much higher than previously anticipated. This thesis has demonstrated 1) the value of involving citizen science into species assessments and specimen collection, 2) the necessity of using molecular data in the species identification process, and 3) the value of molecular methods in the exploration of evolutionary and historical biogeographical patterns to enable us to understand the patterns we find our unique marine realm today.
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