Population genetic structure of the deep-sea mussel Bathymodiolus platifron s (Bivalvia: Mytilidae) in the Northwest Pacific

Ting Xu; Jin Sun; Hiromi K Watanabe; Chong Chen; Masako Nakamura; Rubao Ji; Dong Feng; Jia Lv; Shi Wang; Zhenmin Bao; Pei-Yuan Qian; Jian-Wen Qiu

doi:10.1111/eva.12696

Population genetic structure of the deep-sea mussel Bathymodiolus platifron s (Bivalvia: Mytilidae) in the Northwest Pacific

Evol Appl. 2018 Oct 12;11(10):1915-1930. doi: 10.1111/eva.12696. eCollection 2018 Dec.

Authors

Ting Xu¹, Jin Sun², Hiromi K Watanabe³, Chong Chen³, Masako Nakamura⁴, Rubao Ji⁵, Dong Feng⁶, Jia Lv⁷, Shi Wang^{7

8}, Zhenmin Bao^{7

9}, Pei-Yuan Qian², Jian-Wen Qiu¹

Affiliations

¹ Department of Biology Hong Kong Baptist University Hong Kong China.
² Department of Ocean Science Hong Kong University of Science and Technology Hong Kong China.
³ Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Yokosuka Japan.
⁴ School of Marine Science and Technology Tokai University Shizuoka Japan.
⁵ Department of Biology Woods Hole Oceanographic Institution Woods Hole Massachusetts.
⁶ CAS Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of Oceanology Chinese Academy of Sciences Guangzhou China.
⁷ Ministry of Education Key Laboratory of Marine Genetics and Breeding College of Marine Life Sciences Ocean University of China Qingdao China.
⁸ Laboratory for Marine Biology and Biotechnology Qingdao National Laboratory for Marine Science and Technology Qingdao China.
⁹ Laboratory for Marine Fisheries Science and Food Production Processes Qingdao National Laboratory for Marine Science and Technology Qingdao China.

Abstract

Studying population genetics of deep-sea animals helps us understand their history of habitat colonization and population divergence. Here, we report a population genetic study of the deep-sea mussel Bathymodiolus platifrons (Bivalvia: Mytilidae) widely distributed in chemosynthesis-based ecosystems in the Northwest Pacific. Three mitochondrial genes (i.e., atp6, cox1, and nad4) and 6,398 genomewide single nucleotide polymorphisms (SNPs) were obtained from 110 individuals from four hydrothermal vents and two methane seeps. When using the three mitochondrial genes, nearly no genetic differentiation was detected for B. platifrons in the Northwest Pacific. Nevertheless, when using SNP datasets, all individuals in the South China Sea (SCS) and three individuals in Sagami Bay (SB) together formed one genetic cluster that was distinct from the remaining individuals. Such genetic divergence indicated a genetic barrier to gene flow between the SCS and the open Northwest Pacific, resulting in the co-occurrence of two cryptic semi-isolated lineages. When using 125 outlier SNPs identified focusing on individuals in the Okinawa Trough (OT) and SB, a minor genetic subdivision was detected between individuals in the southern OT (S-OT) and those in the middle OT (M-OT) and SB. This result indicated that, although under the influence of the Kuroshio Current and the North Pacific Intermediate Water, subtle geographic barriers may exist between the S-OT and the M-OT. Introgression analyses based on these outlier SNPs revealed that Hatoma Knoll in the S-OT represents a possible contact zone for individuals in the OT-SB region. Furthermore, migration dynamic analyses uncovered stronger gene flow from Dai-yon Yonaguni Knoll in the S-OT to the other local populations, compared to the reverse directions. Taken together, the present study offered novel perspectives on the genetic connectivity of B. platifrons mussels, revealing the potential interaction of ocean currents and geographic barriers with adaption and reproductive isolation in shaping their migration patterns and genetic differentiation in the Northwest Pacific.

Keywords: Bathymodiolus; RAD‐seq; deep‐sea; genetic structure; introgression; migration patterns; mitochondrial genes; population connectivity.