Deep-Sea Phylogeographic Structure Shaped by Paleoenvironmental Changes and Ongoing Ocean Currents Around the Sea of Japan in a Crangonid Shrimp,Argis lar

Abstract

The deep-sea crangonid shrimp, Argis lar, is a highly abundant species from the northern Pacific Ocean. We investigated its phylogeographic and demographic structure across the species' extensive range, using mitochondrial DNA sequence variation to evaluate the impact of deep-sea paleoenvironmental dynamics in the Sea of Japan on population histories. The haplotype network detected three distinct lineages with allopatric isolation, which roughly corresponded to the Sea of Japan (Lineage A), the northwestern Pacific off the Japanese Archipelago (Lineage B), and the Bering Sea/Gulf of Alaska (Lineage C). Lineage A showed relatively low haplotype and nucleotide diversity, a significantly negative value of Tajima's D, and a star-shaped network, suggesting that anoxic bottom-water in the Sea of Japan over the last glacial period may have brought about a reduction in the Sea of Japan population. Furthermore, unexpectedly, the distributions of Lineage A and B were closely related to the pathways of the two ocean currents, especially along the Sanriku Coast. This result indicated that A. lar could disperse across shallow straits through the ocean current, despite their deep-sea adult habitat. Bayesian inference of divergence time revealed that A. lar separated into three lineages approximately 1 million years before present (BP) in the Pleistocene, and then had been influenced by deep-sea paleoenvironmental change in the Sea of Japan during the last glacial period, followed by a more recent larval dispersal with the ocean current since ca. 6 kilo years BP.

Unexpected low genetic differentiation between Japan and Bering Sea populations of a deep-sea benthic crustacean lacking a planktonic larval stage (Peracarida: Tanaidacea)

“…A pattern similar to our COI haplotype network, where the Bering Sea cluster is more branched and more diverse than the Japan cluster, was observed in the crangonid shrimp Argis lar (Owen, 1839) (Fujita et al, 2017). In that species, however, more nucleotide substitutions (six or 14 substitutions in 571 nt) were detected between a Bering cluster (Lineage C) and Japan clusters (Lineages A and B), indicating older divergences in A. lar than in C. spinigena and that the two species have different evolutionary histories.…”