Cryptic Diversity, Phylogeography and Genetic Connectivity of Abyssorchomene distinctus (Pacific Ocean and SE Indian Ridge)

Polymetallic nodule mining is a growing commercial interest over the past three decades. It is critical to accurately estimate biodiversity before any minerals are exploited in the Clarion-Clipperton Zone (CCZ) in the Northeast Pacific Ocean. Scavenging amphipods are a large group in the abyssal biota and play an important role in the nutrient cycling system. This study uses both mitochondrial (COI) and nuclear (28S rRNA) DNA markers to investigate genetic diversity and connectivity in Abyssorchomene distinctus (Lysianassoidea – Uristidae) (Birstein & Vinogradov, 1960). The genetic sequences of 113 sampled individuals of Abyssorchomene distinctus, which originated from the CCZ, the Discol Experimental Area (DEA), the Atacama Trench and the Southeast Indian Ridge, revealed the absence of cryptic diversity for A. distinctus on a global scale. The findings contrasted with those for other closely related scavenging amphipods, which revealed the presence of cryptic species. Population genetics analyses calculated a low haplotype diversity (Hd) within the A. distinctus population across the Pacific Ocean, while a high Hd was found in the Indian Ocean populations. This is the first study to date providing preliminary indications of a possible genetic connectivity of the scavenging amphipod species Abyssorchomene distinctus between the CCZ and DEA, being geographically separated by a vast distance of 5,000 km. Shared haplotypes were also found between the CCZ, DEA, Atacama Trench and the Southeast Indian Ridge in the COI mitochondrial DNA dataset , which was congruent with results from previous studies on other scavenging amphipods.

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