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Molecular genetics of cirrhitoid fishes (Perciformes: Cirrhitoidea): phylogeny, taxonomy, biogeography, and stock structure


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Burridge, CP 2000 , 'Molecular genetics of cirrhitoid fishes (Perciformes: Cirrhitoidea): phylogeny, taxonomy, biogeography, and stock structure', PhD thesis, University of Tasmania.

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The molecular phylogenetic relationships within three of the five cirrhitoid fish families were
reconstructed from mitochondrial DNA cytochrome b, cytochrome oxidase I, and D-loop
Analysis of the Cheilodactylidae provided evidence that much taxonomic revision is required.
The molecular data suggest that this family should be restricted to the two South African
Cheilodactylus, as they are highly divergent from the other cheilodactylids and one member
is the type species. The remaining 25 cheilodactylids should be transferred to the Latridae.
Nine of the non South African Cheilodactylus can be allocated to three new genera;
Goniistius (elevated to generic rank), Zeodrius (resurrected), and Morwong (resurrected),
while the placement of three species is uncertain. The three South African Chirodactylus
should revert to Palunolepis, as they are distinct from the South American type species
Chirodact_vlus variegatus. Acantholatris clusters within Nemadactylus, ar;d the former should
be synonymised. Cryptic speciation has occurred within Cheilodactylus (Goniistius) vittatus.
The generic allocation of the four latrid species is sound, although this family should be
expanded to encompass all but two cheilodactylids. Relative levels of genetic divergence
within the Aplodactylidae support the most recent revision of this family, during which the
monotypic genus Crinodus was synonymised with Aplodactylus.
Mokcular phylogenetic relationships and estimates of divergence time obtained from
molecular clock calibrations suggest a dominant role of long distance dispersal for the present
distribution of cheilodactylid and aplodactylid fishes. Suggestions that ancestral taxa were
vicariantly isolated during the fragmentation of Gondwana are rejected, as estimated
divergence times appreciably postdate this event. Dispersal and radiation of Nemadactylus
and Acantholatris throughout the Southern Ocean was particularly recent, occurring within
the last 0.6-2.6 Myr. The waters of Australia and New Zealand represent a likely origin for
this dispersal, and at least two events are identified, one eastward. Similarly, it appears that aplodactylids also originated in the waters of Australia and New Zealand, but in this instance
the majority of radiation was undertaken prior to colonisation of the southeastern Pacific.
Ocean currents and long duration offshore pelagic larvae probably facilitated dispersal.
Phylogeographic analysis of the antitropically-distributed cheilodactylid subgenus Goniistius
identified three transequatorial divergences, rather than a minimum of two as inferred from
the distributions of individual taxa. The identified divergences also occurred during two
distinct periods, the mid Miocene and mid to late Pliocene, and are best explained by chance
dispersal or vicariance resulting from biotic interactions or temperature changes.
The levels of genetic separation for three cirrhitoid species pairs with east-west allopatric
distributions across southern Australia reject the possibility that the members of each pair
diverged simultaneously during a shared vicariance event. Although the levels of genetic
separation were similar for Goniistius and Aplodactylus pairs, separate north and south coast
vicariance events are invoked based on likely thermal tolerances. Speciation resulting from
chance dispersal and the founding of new populations is rejected due to the absence of
barriers sufficiently large to isolate taxa with such high dispersal capabilities. Estimated
divergence times fall between the late Miocene and mid Pliocene, and fail to implicate recent
· Pleistocene glaciations.
Seven microsatellite loci were characterised for Nemadactylus macropterus in an effort to
resolve its stock structure in Australian waters and to assess the resolving power of different
molecular techniques. Microsatellites did not identify any stock structuring in the waters of
southern Australia. Divergence was also absent between Australian and New Zealand
populations, which contrasted the findings from allozyme and mitochondrial DNA studies.
Homoplasy of alleles at highly polymorphic loci is offered as a possible explanation for the
lower resolution of stock structure obtained with microsatellites.The microsatellites characterised for N. macropterus were also employed to examine the
taxonomic status of the morphologically similar S0uth American species N. bergi. Separate
status was supported by divergence at a single locus. Microsatellites also provided evidence
for a recent bottleneck in the effective population size of N. bergi, but not N. macropterus or
A. monodactylus. Based on this observation, the mitochondrial DNA lineage monophyly
observed for N. hergi, but not N. macropterus or A. monodactylus, may reflect the influence
of effective population size on the time required for complete sorting of mitochondrial

Item Type: Thesis - PhD
Authors/Creators:Burridge, CP
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