Genetic origins and climate-induced erosion in economically important Asian walnuts

Fan P.-Z. Zhu G.-F. Wambulwa M.C. Milne R.I. Wu Z.-Y. Luo Y.-H. Shahi Shavvon R. Jump A.S. Maity D. Gao L.-M. Qi H.-L. Wu H.-Y. Kong X. Khan R. Yan L.-J. Turuspekov Y. Li D.-Z. Liu J.
February 2026 John Wiley and Sons Inc

Conservation Biology
2026 #40 Issue 1

The global climate is undergoing unprecedented changes, posing significant threats to species persistence. However, the spatiotemporal impacts on genetic diversity remain poorly understood, hindering species conservation and management. Walnuts, generally referred to as Juglans regia and J. sigillata, are economically vital in Asia, but little is known about their genetic origins and how the species will be affected by future climate change. Using 31 microsatellites, we genotyped 5282 individuals from 233 populations of walnuts in Asia. We assessed genetic diversity patterns and demographic history and investigated potential future genetic erosion risks. Genetic diversity of walnuts was high in the Himalaya and Hengduan Mountains. The 2 species diverged during the Pleistocene (around 1.41 Ma BP), and J. regia contained 2 genetic groups (JR1 and JR2). The JR2 group had the lowest diversity and likely arrived in northern China around 9.77 ka BP, perhaps via human transport. The Western Himalaya likely served both as a glacial refugium and the center of origin for J. regia, and the Eastern Himalaya appears to have been the refugium for J. sigillata. The 2 species appear to have hybridized in the Central Himalaya and the Sichuan basin and surroundings, forming two distinct hybrid zones. Our results indicate that genetic diversity will be reduced by up to 9.03% due to range loss under future climate change and dramatic genetic structure turnover in the Himalaya and Hengduan Mountains. In situ conservation in the Himalaya is essential for safeguarding genetic diversity and adaptive potential in Asian walnuts, while ex situ preservation of genetically unique wild germplasm, coupled with its integration into breeding programs, will enhance climate resilience. The findings advance our understanding of the origin of Asian walnuts and how future climatic change may affect their genetic diversity, offering a model for conservation and breeding strategies in other tree species facing similar threats.

cambio climático , climate change , conectividad entre paisajes , diversidad genética , ecological niche modeling , erosión genética , genetic diversity , genetic erosion , Juglans regia , Juglans sigillata , landscape connectivity , modelos de nicho ecológico , 景观联通性 , 气候变化 , 泡核桃 , 胡桃 , 遗传侵蚀 , 遗传多样性

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CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
University of the Chinese Academy of Sciences, Beijing, China
Department of Life Sciences, School of Science and Computing, South Eastern Kenya University, Kitui, Kenya
Institute of Molecular Plant Sciences, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
Lijiang Forest Biodiversity National Observation and Research Station, Kunming Institute of Botany, Chinese Academy of Sciences, Lijiang, China
Department of Biology, Faculty of Science, Yasouj University, Yasuj, Iran
Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, United Kingdom
Department of Botany, University of Calcutta, Kolkata, India
Center for Integrative Conservation & Yunnan Key Laboratory for the Conservation of Tropical Rainforests and Asian Elephants, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, China
Laboratory of Molecular Genetics, Institute of Plant Biology and Biotechnology, Almaty, Kazakhstan

CAS Key Laboratory for Plant Diversity and Biogeography of East Asia
Germplasm Bank of Wild Species & Yunnan Key Laboratory of Crop Wild Relatives Omics
University of the Chinese Academy of Sciences
Department of Life Sciences
Institute of Molecular Plant Sciences
Lijiang Forest Biodiversity National Observation and Research Station
Department of Biology
Biological and Environmental Sciences
Department of Botany
Center for Integrative Conservation & Yunnan Key Laboratory for the Conservation of Tropical Rainforests and Asian Elephants
Laboratory of Molecular Genetics

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