Plant Diversity ›› 2024, Vol. 46 ›› Issue (02): 181-193.DOI: 10.1016/j.pld.2023.08.003

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Enhanced and asymmetric signatures of hybridization at climatic margins: Evidence from closely related dioecious fig species

Jian-Feng Huanga, Clive T. Darwellb, Yan-Qiong Penga   

  1. a. CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, China;
    b. National Center for Genetic Engineering and Biotechnology (BIOTEC), 113 Thailand Science Park, Phahonyothin Road, Khlong Nueng, Khlong Luang, Pathum Thani 12120, Thailand
  • Received:2023-03-23 Revised:2023-08-17 Online:2024-03-25 Published:2024-04-07
  • Contact: Jian-Feng Huang,;Yan-Qiong Peng,
  • Supported by:
    This work was supported by the National Natural Science Foundation of China (31800313; 32261123001), Applied Basic Research Foundation of Yunnan Province (202301AT070378, 2019FB034), the “Light of West China” Program of the Chinese Academic of Sciences to J.-F. Huang, and Guangzhou Collaborative Innovation Center on Science-tech of Ecology and Landscape.

Abstract: Hybridization plays a significant role in biological evolution. However, it is not clear whether ecological contingency differentially influences likelihood of hybridization, particularly at ecological margins where parental species may exhibit reduced fitnesses. Moreover, it is unknown whether future ecosystem change will increase the prevalence of hybridization. Ficus heterostyla and F. squamosa are closely related species co-distributed from southern Thailand to southwest China where hybridization, yielding viable seeds, has been documented. As a robust test of ecological factors driving hybridization, we investigated spatial hybridization signatures based on nuclear microsatellites from extensive population sampling across a widespread contact range. Both species showed high population differentiation and strong patterns of isolation by distance. Admixture estimates exposed asymmetric interspecific gene flow. Signatures of hybridization increase significantly towards higher latitude zones, peaking at the northern climatic margins. Geographic variation in reproductive phenology combined with ecologically challenging marginal habitats may promote this phenomenon. Our work is a first systematic evaluation of such patterns in a comprehensive, latitudinally-based clinal context, and indicates that tendency to hybridize appears strongly influenced by environmental conditions. Moreover, that future climate change scenarios will likely alter and possibly augment cases of hybridization at ecosystem scales.

Key words: Hybridization, Heterospecific visitation, Fig, Pollinator wasp, Asymmetric gene flow