Climate Change Threatens Genetic Diversity of Asian Walnuts

Strategic Insights -

As the global climate undergoes unprecedented changes, threatening species persistence, new research reveals the significant impact of climate change on the genetic diversity of Asian walnuts. A team of scientists from the Chinese Academy of Sciences conducted a comprehensive study, evaluating the genetic diversity patterns and demographic history of walnuts in Asia. Their findings indicate that genetic diversity will be reduced by up to 9.03% due to range loss under future climate change. 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.

Key Takeaways:

  • The global climate is undergoing unprecedented changes, posing significant threats to species persistence, particularly in Asian walnuts.
  • Genetic diversity of walnuts was high in the Himalaya and Hengduan Mountains, with the 2 species diverging during the Pleistocene era (around 1.41 million years ago).
  • The JR2 group had the lowest diversity and likely arrived in northern China around 9.77 thousand years ago, perhaps via human transport.
  • The Western Himalaya likely served as a glacial refugium and the center of origin for J. regia, while the Eastern Himalaya appears to have been the refugium for J. sigillata.
  • Hybridization between the two species occurred in the Central Himalaya and the Sichuan basin and surroundings, forming two distinct hybrid zones.
  • 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.

Statistics:

  • 31 microsatellites were used to genotype 5282 individuals from 233 populations of walnuts in Asia.
  • The JR2 group contained the highest genetic diversity among the populations studied (34.48%).
  • Genetically unique wild germplasm was preserved in 26.37% of the populations studied.
  • Range loss under future climate change is estimated to reduce genetic diversity by up to 9.03% in the Himalaya and Hengduan Mountains.

Sources:

  • Genetic origins and climate-induced erosion in economically important Asian walnuts. Conservation Biology, 2025.
  • Conservation Biology, Wiley, 111 River St, Hoboken 07030-5774, NJ, USA. (Wiley-Blackwell - www.wiley.com/; Conservation Biology - onlinelibrary.wiley.com/journal/10.1111/(ISSN)1523-1739)
  • Guang-Fu Zhu, CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, People's Republic of China.
  • Peng-Zhen Fan, Moses C. Wambulwa, Richard I. Milne, Zeng-Yuan Wu, Ya-Huang Luo, Robabeh Shahi Shavvon, Alistair S. Jump, Debabrata Maity, Lian-Ming Gao, Hai-Ling Qi, Hong-Yu Wu, Xing Kong, Raees Khan, Li-Jun Yan, Yerlan Turuspekov, and De-Zhu L.