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A systematic and phylogenetic revision of the deepsea genera Anthothela and Primnoisis (Coelenterata Octocorallia: Alcyonacea) and an exploration of the biogeography of Primnoisis

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Moore, KM (2014) A systematic and phylogenetic revision of the deepsea genera Anthothela and Primnoisis (Coelenterata Octocorallia: Alcyonacea) and an exploration of the biogeography of Primnoisis. PhD thesis, University of Tasmania.

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Abstract

Octocorals have been recognised as abundant and ecologically significant on many deep-sea
features. However their taxonomy and distribution remains poorly understood due to inadequate
historical literature and a paucity of definitive morphological characteristics, and this is now
hindering conservation and management in many of our important deep-sea marine ecosystems.
For example, a decadal study of fishing impacts on seamounts south of Tasmania, Australia revealed
a great diversity of octocorals, including two commonly collected and widely distributed genera,
Anthothela and Primnoisis, but specimens could not be identified to species due to taxonomic
confusion within the groups and hence could not be considered in diversity assessments and
conservation measures. The taxonomy of these genera is revised herein in order to prescribe genus
and species level morphological definitions, phylogeny and geographical extent. A multi-disciplinary
approach was used combining morphological characteristics such as colonial branching patterns,
polyp structure and sclerite form and arrangement, and phylogenetic reconstructions using two
mitochondrial gene regions (mtMutS and igr1–COI).
Anthothela (Family Anthothelidae), with six nominal species globally, is here divided into four
genera, two of which are new. Anthothela is found to have three valid species, A. grandiflora,
A. pacifica and A. tropicalis, another species Spongioderma (?) vickersi is reassigned to Anthothela
and two new species A. aldersladei and A. quattriniae, are described. Anthothela argentea and
A. nuttingi are reassigned to Victorgorgia (Family Anthothelidae) and two new species of this genus,
V. eminens and V. nyahae are described. These are the first records of Anthothela and Victorgorgia
from Australia. One new genus, Williamsius, is described for A. parviflora, which is restricted to
South African waters, and Lateothela anitorkilda n. gen., n. sp. is described to incorporate north
Atlantic Ocean specimens which have been traditionally been mistaken for A. grandiflora. There was
good congruence between morphological characteristics and molecular data at a generic level, but
at the species-level morphological and genetic variation was very low. Anthothela and Lateothela n.
gen. are found to be closely related to some nominal Alcyonium species and the Family
Anthothelidae is shown to be paraphyletic.
The genus Primnoisis (Isididae) is retained with 7 of the 8 nominal species, P. antarctica, P. rigida,
P. ambigua, P. delicatula, P. fragilis, P. formosa, P. mimas, validated and the eighth, P. sparsa is
synonymised with P. antarctica. In addition, the species Mopsea gracilis is reassigned to Primnoisis
and five new species are described; P. chatham, P. erymna, P. millerae, P. niwa and P. tasmani.
Most of the species fell into two clear groups, defined both by morphology and genetics, for which
two new sub-genera are proposed (P. (Primnoisis) and (P. Delicatisis)). Three species, P. ambigua, P. mimas and P. tasmani n. sp., could not be placed reliably in either sub-genus due to distinctive
morphological features or genetic dissimilarity. It was not possible to confirm the monophyly of the
genus due to unresolved relationships with the closely related genus Notisis and an undescribed
Mopseinae genus. P. tasmani n. sp., with a distribution restricted to the southeast of Australia, is
positioned basal to all other Primnoisis species based on DNA sequence data, suggesting southern
Australia as the origin of the genus, with subsequent vicariant speciation after the separation of
Gondwana and initiation of the Antarctic Circumpolar Current (ACC). North of the ACC, species are
restricted to general geographical features such as seamount complexes, ridges and plateaus. Three
species recorded south of the ACC are found to have extensive distributions around the Antarctic
continental shelf and two further species appear to be widely distributed. P. millerae n. sp. is found
to be separated by depth from other species on the Antarctic continental shelf and P. fragilis
appears to have limited connectivity between vastly separated Antarctic populations, although low
variability in the gene regions used and small sample size prohibit definitive conclusions.
These results illustrate significant undescribed diversity in the octocorals of the Southern Ocean and
indicate that without comprehensive taxonomic reviews, current biodiversity estimates are likely to
be grossly inaccurate, even at a genus level. This research will facilitate future ecological and
conservation research on these octocorals by allowing more robust identification, and producing
accurate geographic distributions and connectivity assessments. These in turn will guide
conservation efforts to protect these poorly understood deep-sea communities.

Item Type: Thesis (PhD)
Keywords: taxonomy, octocorals, deep-sea, phylogenetics, morphology, biogeography
Copyright Holders: The Author
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Copyright 2014 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Date Deposited: 23 Mar 2016 00:52
Last Modified: 01 Dec 2016 16:00
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