Abstract
In the ancillariid genus Amalda, the shell is character rich and 96 described species are currently treated as valid. Based on shell morphology, several subspecies have been recognized within Amalda hilgendorfi, with a combined range extending at depths of 150–750 m from Japan to the South-West Pacific. A molecular analysis of 78 specimens from throughout this range shows both a weak geographical structuring and evidence of gene flow at the regional scale. We conclude that recognition of subspecies (richeri Kilburn & Bouchet, 1988, herlaari van Pel, 1989, and vezzaroi Cossignani, 2015) within A. hilgendorfi is not justified. By contrast, hilgendorfi-like specimens from the Mozambique Channel and New Caledonia are molecularly segregated, and so are here described as new, as Amalda miriky sp. nov. and A. cacao sp. nov., respectively. The New Caledonia Amalda montrouzieri complex is shown to include at least three molecularly separable species, including A. allaryi and A. alabaster sp. nov. Molecular data also confirm the validity of the New Caledonia endemics Amalda aureomarginata, A. fuscolingua, A. bellonarum, and A. coriolis. The existence of narrow range endemics suggests that the species limits of Amalda with broad distributions, extending, e.g., from Japan to Taiwan (A. hinomotoensis) or even Indonesia, the Strait of Malacca, Vietnam and the China Sea (A. mamillata) should be taken with caution.
Highlights
Extreme threshold values led to partitions where each of the 64 Cox1 haplotypes of Amalda was considered as a different Primary Species Hypothesis (PSH), or where almost all haplotypes were considered as a single PSH
The 17 PSHs supported by both the shell morphology and the genetic clustering were hereafter treated as Secondary Species Hypotheses (SSH)
Amalda cacao sp. nov. and A. hilgendorfi are broadly distributed in the New Caledonia EEZ, while A. bellonarum and A. coriolis are found only in the Coral Sea, and A. alabaster sp. nov., A. fuscolingua, A. allaryi, A. montrouzieri, A. herberti and A. aureomarginata are confined to southern New Caledonia
Summary
The genus includes 96 Recent species, classified in seven nominal subgenera (Kantor et al 2017), some of them at times treated as full genera. Gemmel et al (2020) presented a molecular phylogeny based on the entire mitogenome and long nuclear rRNA gene cassette data, targeting primarily New Zealand species of Amalda. Until the recent paper by Gemmel et al (2020), Amalda has remained practically overlooked from the molecular point of view, with sequences of only 5 species deposited in GenBank, essentially originating from the molecular phylogeny of the superfamily Olivoidea by Kantor et al (2017). These included species attributed to the subgenera Baryspira P. Sowerby II, 1859); as well as six Indo-Pacific species, mostly based on the MNHN collections that form the basis of the present paper
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