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Ito S, Yamazaki D, Kameda Y, Kagawa O, Ye B, Saito T, Kimura K, Do VT, Chiba S, Hirano T. Taxonomic insights and evolutionary history in East Asian terrestrial slugs of the genus Meghimatium. Mol Phylogenet Evol 2023; 182:107730. [PMID: 36781029 DOI: 10.1016/j.ympev.2023.107730] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 01/26/2023] [Accepted: 02/08/2023] [Indexed: 02/13/2023]
Abstract
East Asia, specifically the Japanese Archipelago, is a biodiversity hotspot of both vertebrates and invertebrates. Mollusks represent a burst of species diversity in this region due to the effects of biotic and abiotic factors on their morphological traits, such as shell shape and size. However, the evolutionary history of terrestrial slugs in East Asia remains unknown. In the present study, we investigated the molecular phylogeny of terrestrial slugs of the genus Meghimatium. This genus includes three described and eight undescribed species, and our study used all except for two. Based on phylogeny and the species delimitation tests, the genus Meghimatium was split into many putative species, suggesting higher species diversity than previously thought based on morphological and anatomical studies and that almost undescribed species may be inappropriate. Therefore, morphological traits, such as body size and colour, conventionally considered for classification may easily vary or be similar across geographic region. Moreover, the divergence time of this genus is almost concordant with the geographical time scale of the formation of the Japanese mainland. Our findings suggest that molecular phylogenetics helps classify Japanese Meghimatium slugs, but comprehensive taxonomic revisions using multi-locus analyses are needed.
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Affiliation(s)
- Shun Ito
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Graduate School of Life Science, Tohoku University, Miyagi, Japan.
| | - Daishi Yamazaki
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Faculty of Agriculture and Marine Science, Kochi University, Kochi, Japan
| | - Yuichi Kameda
- Department of Anthropology, National Museum of Nature and Science, Ibaraki, Japan
| | - Osamu Kagawa
- Graduate School of Life Science, Tohoku University, Miyagi, Japan; Shimoda Marine Research Center, University of Tsukuba, Shizuoka, Japan
| | - Bin Ye
- Graduate School of Life Science, Tohoku University, Miyagi, Japan; Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, China
| | - Takumi Saito
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Department of Botany and Zoology, Faculty of Science, Masaryk University, Czech Republic
| | - Kazuki Kimura
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Research Institute for Ulleung-do and Dok-do islands, Department of Biology, Kyungpook National University, Buk-gu, South Korea
| | - Van Tu Do
- Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Hanoi, Viet Nam; Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Viet Nam
| | - Satoshi Chiba
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Graduate School of Life Science, Tohoku University, Miyagi, Japan
| | - Takahiro Hirano
- Center for Northeast Asian Studies, Tohoku University, Miyagi, Japan; Graduate School of Life Science, Tohoku University, Miyagi, Japan; Biology Program, Faculty of Science, University of the Ryukyus, Okinawa, Japan
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Resolving species-level diversity of Beringiana and Sinanodonta mussels (Bivalvia: Unionidae) in the Japanese archipelago using genome-wide data. Mol Phylogenet Evol 2022; 175:107563. [PMID: 35809852 DOI: 10.1016/j.ympev.2022.107563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 06/04/2022] [Accepted: 06/27/2022] [Indexed: 11/22/2022]
Abstract
Accurate species identification is of primary importance in ecology and evolutionary biology. For a long time, the unionid mussels Beringiana and Sinanodonta have puzzled researchers trying to unravel their diversity because of their poorly discernible morphologies. A recent study conducted species delineation of unionid mussels based on mitochondrial DNA variation, opening up a new avenue to grasp species diversity of the mussels. However, mtDNA-based classification may not align with species boundaries because mtDNA is prone to introgression and incomplete lineage sorting that cause discordance between species affiliation and gene phylogeny. In this study, we evaluated the validity of the mtDNA-based classification of unionid mussels Beringiana and Sinanodonta in Japan using mitochondrial sequence data, double digest restriction site-associated DNA library (ddRAD) sequencing, and morphological data. We found significant inconsistencies in the mitochondrial and nuclear DNA phylogenies, casting doubt on the reliability of the mtDNA-based classification in this group. In addition, nuclear DNA phylogeny revealed that there are at least two unionid lineages hidden in the mtDNA phylogeny. Although molecular dating technique indicates that Beringiana and Sinanodonta diverged >35 million years ago, their shell morphologies are often indistinguishable. Specifically, morphological analyses exhibited the parallel appearance of nearly identical ball-like shell forms in the two genera in Lake Biwa, which further complicates species identification and the morphological evolution of unionid mussels. Our study adds to a growing body of literature that accurate species identification of unionid mussels is difficult when using morphological characters alone. Although mtDNA-based classification is a simple and convenient way to classify unionid mussels, considerable caution is warranted for its application in ecological and evolutionary studies.
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