J Integr Plant Biol ›› 2024, Vol. 66 ›› Issue (6): 1170-1191.DOI: 10.1111/jipb.13638

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  • 收稿日期:2023-06-06 接受日期:2024-02-23 出版日期:2024-06-01 发布日期:2024-06-25

Eco-evolutionary evidence for the global diversity pattern of Cycas(Cycadaceae)

Jian Liu1,2,3, Anders J. Lindstrom4, Yiqing Gong5, Shanshan Dong5, Yusheng (Chris) Liu6, Shouzhou Zhang5* and Xun Gong1,2,3*   

  1. 1. CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China;
    2. Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China;
    3. University of Chinese Academy of Sciences, Beijing 100049, China;
    4. Global Biodiversity Conservancy, 144/124 Moo3, Soi Bua Thong, Bangsalae, Sattahip, Chonburi 20250, Thailand;
    5. Key Laboratory of Southern Subtropical Plant Diversity, Fairy Lake Botanical Garden, Shenzhen & Chinese Academy of Sciences, Shenzhen 518004, China;
    6. Department of Earth and Environmental Sciences, Indiana University-Indianapolis, Indianapolis, IN 46202, USA
    *Correspondences: Shouzhou Zhang (shouzhouz@szbg.ac.cn); Xun Gong (gongxun@mail.kib.ac.cn, Dr. Gong is fully responsible for the distributions of all materials associated with this article)
  • Received:2023-06-06 Accepted:2024-02-23 Online:2024-06-01 Published:2024-06-25

Abstract: The evolution of the latitudinal diversity gradient (LDG), characterized by a peak in diversity toward the tropics, has captured significant attention in evolutionary biology and ecology. However, the inverse LDG (i-LDG) mechanism, wherein species richness increases toward the poles, remains inadequately explored. Cycads are among one of the oldest lineages of extant seed plants and have undergone extensive diversification in the tropics. Intriguingly, the extant cycad abundance exhibits an i-LDG pattern, and the underlying causes for this phenomenon remain largely elusive. Here, using 1,843 nuclear genes from a nearly complete sampling, we conducted comprehensive phylogenomic analyses to establish a robust species-level phylogeny for Cycas, the largest genus within cycads. We then reconstructed the spatial-temporal dynamics and integrated global environmental data to evaluate the roles of species ages, diversification rates, contemporary environment, and conservatism to ancestral niches in shaping the i-LDG pattern. We found Cycas experienced decreased diversification rates, coupled with the cooling temperature since its origin in the Eocene from continental Asia. Different regions have distinctively contributed to the formation of i-LDG for Cycas, with the northern hemisphere acting as evolutionary museums and the southern hemisphere serving as cradles. Moreover, water-related climate variables, specifically precipitation seasonality and potential evapotranspiration, were identified as paramount factors constraining Cycas species richness in the rainforest biome near the equator. Notably, the adherence to ancestral monsoonal climates emerges as a critical factor in sustaining the diversity pattern. This study underscores the imperative of integrating both evolutionary and ecological approaches to comprehensively unravel the mechanisms underpinning global biodiversity patterns.

Key words: cycads, latitudinal diversity gradient, niche conservatism, spatiotemporal diversification, species richness

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