Abstract
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.
Highlights
The genus Nautilus (Mollusca, Cephalopoda) belongs to subclass Nautiloidea that has an extensive fossil record dating back to the Devonian (Teichert and Matsumoto 1987; Kro€ger et al 2011)
Using concatenated 16S-c oxidase I (COI) sequences analyzed by Bayesian statistics, samples from Fiji, American Samoa, Philippines, a 2016 The Authors
Some individuals from the Great Barrier Reef were identified in previous studies as the species N. stenomphalus (Saunders 1987; Bonacum et al 2011), our rigorous phylogenetic analyses show that sequences from these samples are indistinguishable from those of N. pompilius (Fig. 3)
Summary
The genus Nautilus (Mollusca, Cephalopoda) belongs to subclass Nautiloidea that has an extensive fossil record dating back to the Devonian (Teichert and Matsumoto 1987; Kro€ger et al 2011). We will refer to Nautilus as the genus and nautilus when discussing the animal itself. Because members of the extant Nautilus genus have been hypothesized to have evolved in their current form between 7 and 10 mya (Ward 1984) or possibly much earlier, approximately 40 mya (Teichert and Matsumoto 1987; Woodruff et al 1987), and modern nautiluses appear to be very similar to some of their Mesozoic ancestors (Ward and Saunders 1997), these animals have been described as “living fossils” (Sinclair et al 2011). Extant nautilids are limited in their ability to disperse: they are obligately nektobenthic, do not swim far off the sea floor, and have rarely been observed in mid-
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