TY - JOUR
T1 - Refugia during the last glacial period and the origin of the disjunct distribution of an insular plant
AU - Yamada, Takayuki
AU - Kokubugata, Goro
AU - Fujii, Shinji
AU - Chen, Chien Fan
AU - Asakawa, Akira
AU - Ito, Takuro
AU - Maki, Masayuki
N1 - Funding Information:
We are very grateful to all of the following for plant samples, comments, and technical advice: Drs. K. Yonekura, M. Oyama, S. Horie, Messrs. T. Kimura, H. Goto, R. Henmi, and the members of the Botanical Garden, Tohoku University; Drs. T. Hosoya, K. Hosaka, A. Ebihara, and the members of the Department of Botany, National Museum of Nature and Science; Drs. N. Nagata, S. Kakishima, Y. Kameda, N. Yoshikawa, S. Hiruta, S. Chiba, H. Umemoto, and the members of the Center for Molecular Biodiversity Research, National Museum of Nature and Science; Dr. M. Yokota, University of the Ryukyus. We also thank the members of the Tourist Association of Mikura Island for their help during our stays on the island. This study was partly supported by a Grant‐in‐Aid from the Japan Society for the Promotion of Science to MM. No specific permits were needed to conduct this study.
Publisher Copyright:
© 2021 John Wiley & Sons Ltd
PY - 2021
Y1 - 2021
N2 - Aim: Although many phylogeographic studies have focused on continental refugia, the roles of islands as refugia have long been overlooked. In this study, we conducted phylogeographic studies of a plant with insular distribution, Microtropis japonica, to elucidate the potential roles of islands as refugia during recent glacial periods. Specifically, we test the hypothesis that two remote groups of Japanese islands (the Izu and Ryukyu Islands) were refugia for M japonica. Location: The Izu and Ryukyu Islands of Japan and their adjacent areas including the Japanese mainland and Taiwan. Taxon: Microtropis japonica (Celastraceae). Methods: A total of 363 individuals were sampled from 44 populations of M japonica. To elucidate population genetic differentiation and demographic change in M japonica, we performed molecular variance and mismatch distribution analyses based on chloroplast DNA (cpDNA) sequence variations and Bayesian clustering and gene flow estimates based on nuclear single-nucleotide polymorphism (SNP) data. In addition, to examine distribution changes, ecological niche modelling using the maximum entropy method was used to determine suitable habitats existing currently or during the last glacial maximum, using occurrence data and six bioclimatic variables. Results: Both cpDNA and nuclear SNP data showed genetic differentiation between two disjunct regions. However, cpDNA data indicated genetic differentiation within the Ryukyu Islands but not within the Izu Islands, while nuclear SNP data indicated genetic differentiation within both island groups. Ecological niche modelling showed that both the Izu and Ryukyu archipelagos had contained some islands with a climate compatible with modern M japonica climate envelopes despite climate oscillations. Main conclusions: Islands within both the Izu and Ryukyu archipelagos may have supported M japonica populations throughout historical climate oscillations. The current disjunct distribution of M japonica strongly reflects its refugial locations during the last glacial period and the subsequent range expansion. Islands were important refuges, contributing to the modern disjunct distribution of M japonica.
AB - Aim: Although many phylogeographic studies have focused on continental refugia, the roles of islands as refugia have long been overlooked. In this study, we conducted phylogeographic studies of a plant with insular distribution, Microtropis japonica, to elucidate the potential roles of islands as refugia during recent glacial periods. Specifically, we test the hypothesis that two remote groups of Japanese islands (the Izu and Ryukyu Islands) were refugia for M japonica. Location: The Izu and Ryukyu Islands of Japan and their adjacent areas including the Japanese mainland and Taiwan. Taxon: Microtropis japonica (Celastraceae). Methods: A total of 363 individuals were sampled from 44 populations of M japonica. To elucidate population genetic differentiation and demographic change in M japonica, we performed molecular variance and mismatch distribution analyses based on chloroplast DNA (cpDNA) sequence variations and Bayesian clustering and gene flow estimates based on nuclear single-nucleotide polymorphism (SNP) data. In addition, to examine distribution changes, ecological niche modelling using the maximum entropy method was used to determine suitable habitats existing currently or during the last glacial maximum, using occurrence data and six bioclimatic variables. Results: Both cpDNA and nuclear SNP data showed genetic differentiation between two disjunct regions. However, cpDNA data indicated genetic differentiation within the Ryukyu Islands but not within the Izu Islands, while nuclear SNP data indicated genetic differentiation within both island groups. Ecological niche modelling showed that both the Izu and Ryukyu archipelagos had contained some islands with a climate compatible with modern M japonica climate envelopes despite climate oscillations. Main conclusions: Islands within both the Izu and Ryukyu archipelagos may have supported M japonica populations throughout historical climate oscillations. The current disjunct distribution of M japonica strongly reflects its refugial locations during the last glacial period and the subsequent range expansion. Islands were important refuges, contributing to the modern disjunct distribution of M japonica.
KW - Izu Islands
KW - Japan
KW - MIG-seq
KW - Ryukyu Islands
KW - ecological niche modelling
KW - insular distribution
KW - last glacial maximum
KW - long-distance dispersal
KW - phylogeography
KW - population genetics
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U2 - 10.1111/jbi.14090
DO - 10.1111/jbi.14090
M3 - Article
AN - SCOPUS:85101754696
JO - Journal of Biogeography
JF - Journal of Biogeography
SN - 0305-0270
ER -