A Revisited Phylogeography of Nautilus Pompilius

The cephalopod genus Nautilus is considered a “living fossil” with a contested number of extant and extinct species, and a benthic lifestyle that limits movement of animals between isolated seamounts and landmasses in the Indo-Pacific. Nautiluses are fished for their shells, most heavily in the Philippines, and these fisheries have little monitoring or regulation. Here, we evaluate the hypothesis that multiple species of Nautilus (e.g., N. belauensis, N. repertus and N. stenomphalus) are in fact one species with a diverse phenotypic and geologic range. Using mitochondrial markers, we show that nautiluses from the Philippines, eastern Australia (Great Barrier Reef), Vanuatu, American Samoa, and Fiji fall into distinct geographical clades. For phylogenetic analysis of species complexes across the range of nautilus, we included sequences of Nautilus pompilius and other Nautilus species from GenBank from localities sampled in this study and others. We found that specimens from Western Australia cluster with samples from the Philippines, suggesting that interbreeding may be occurring between those locations, or that there is limited genetic drift due to large effective population sizes. Intriguingly, our data also show that nautilus identified in other studies as N. belauensis, N. stenomphalus, or N. repertus are likely N. pompilius displaying a diversity of morphological characters, suggesting that there is significant phenotypic plasticity within N. pompilius

Three new species of Nautilus Linnaeus, 1758 (Mollusca, Cephalopoda) from the Coral Sea and South Pacific

Nautiloids are a charismatic group of marine molluscs best known for their rich fossil record, but today they are restricted to a handful of species in the family Nautilidae from around the Coral Triangle. Recent genetic work has shown a disconnect between traditional species, originally defined on shell characters, but now with new findings from genetic structure of various Nautilus populations. Here, three new species of Nautilus from the Coral Sea and South Pacific region are formally named using observations of shell and soft anatomical data augmented by genetic information: N. samoaensis sp. nov. (from American Samoa), N. vitiensis sp. nov. (from Fiji), and N. vanuatuensis sp. nov. (from Vanuatu). The formal naming of these three species is timely considering the new and recently published information on genetic structure, geographic occurrence, and new morphological characters, including color patterns of shell and soft part morphology of hood, and will aid in managing these possibly endangered animals. As recently proposed from genetic analyses, there is a strong geographic component affecting taxonomy, with the new species coming from larger island groups that are separated by at least 200 km of deep water (greater than 800 m) from other Nautilus populations and potential habitats. Nautilid shells implode at depths greater than 800 m and depth therefore acts as a biogeographical barrier separating these species. This isolation, coupled with the unique, endemic species in each locale, are important considerations for the conservation management of the extant Nautilus species and populations

a–d. Photographic identification of nautiluses at each location.

<p>Photographs of nautiluses taken from the underwater video footage from Australia (1a), Fiji (1b), American Samoa (1c), and the Philippines (1d).</p

Population abundance values of the each location sampled including prior data from Osprey Reef, Australia¹⁰ representing all currently sampled <i>Nautilus</i> populations.

<p>Population abundance values of the each location sampled including prior data from Osprey Reef, Australia¹⁰ representing all currently sampled <i>Nautilus</i> populations.</p

The Great Barrier Reef and Coral Sea

The Coral Sea lies in the southwestern Pacific Ocean, bordered by Australia, Papua New Guinea, the Solomon Islands, Vanuatu, New Caledonia, and the Tasman Sea. The Great Barrier Reef (GBR) constitutes the western margin of the Coral Sea and supports extensive submerged reef systems in mesophotic depths. The majority of research on the GBR has focused on Scleractinian corals, although other taxa (e.g., fishes) are receiving increasing attention. To date, 192 coral species (44% of the GBR total) are recorded from mesophotic depths, most of which occur shallower than 60 m. East of the Australian continental margin, the Queensland Plateau contains many large, oceanic reefs. Due to their isolated location, Australia's Coral Sea reefs remain poorly studied; however, preliminary investigations have confirmed the presence of mesophotic coral ecosystems, and the clear, oligotrophic waters of the Coral Sea likely support extensive mesophotic reefs. Although mesophotic reefs in the GBR and Coral Sea are among the best-studied globally, most research has focused on only a few sites, and research effort dedicated to mesophotic coral ecosystems remains negligible compared to shallow-water reefs. Despite the lack of ecological data from most mesophotic reef habitats, precautionary management approaches that explicitly considered latitudinal and cross-shelf gradients in the environment resulted in mesophotic reefs being well-represented in no-take areas in the GBR. In contrast, mesophotic reefs in the Coral Sea currently receive little protection