Speciation and conservation genetic assessment of two endangered cycad species,Journal of Systematics and Evolution

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Speciation and conservation genetic assessment of two endangered cycad species
Journal of Systematics and Evolution ( IF 3.4 ) Pub Date : 2023-12-07 , DOI: 10.1111/jse.13031
Xiu‐Yan Feng _{1,

2} , Yi‐Qing Gong ₃ , Khang Sinh Nguyen _{4,

5} , Hiep Tien Nguyen ₆ , Yong‐Bo Liu ₇ , Jian Liu _{1,

2} , Xun Gong _{1,

2}

Affiliation

Understanding the driving forces of speciation is a central question in evolutionary biology. Cycas bifida (Dyer) K. D. Hill and Cycas micholitzii Dyer are two morphologically similar Cycas (Cycadaceae) species with deeply pectinate megasporophylls and dichotomously divided leaflets. Geographically, they are isolated by the Red River Fault Zone (RRFZ), which acts as a biogeographical barrier for many Cycas species. In this study, we investigated the divergence, genetic diversity, genetic structure, and demographic history of C. bifida and C. micholitzii to uncover the speciation mechanisms for the two endangered species. Results revealed high historical gene flow but low contemporary gene flow between the two species, with a deep divergence occurring in the Late Miocene. The long-term geographical isolation and ecological niche differentiation were identified as important factors in driving the divergence of the two species, supported by significant isolation by distance testing, barrier analysis, and niche consistency detection. Geographical isolation by the RRFZ played a pivotal role in facilitating their divergence by constraining gene flow. Conservation genetic analyses indicated high genetic diversity within both species, coupled with disparate responses to Pleistocene climate fluctuations: C. micholitzii experienced population expansion, while C. bifida displayed a mild bottleneck effect. To ensure the protection and long-term sustainability of two threatened species, relevant conservation guidelines were proposed based on the assessment of their genetic diversity and structure. This study furnishes valuable insights into the mechanisms underpinning species divergence and delivers actionable recommendations for cycad conservation.

中文翻译：

两种濒危苏铁物种的物种形成和保护遗传评估

了解物种形成的驱动力是进化生物学的核心问题。Cycas bifida (Dyer) KD Hill 和Cycas micholitzii Dyer 是两种形态相似的苏铁属（苏铁科）物种，具有深梳状大孢子叶和二歧式小叶。在地理上，它们被红河断裂带（RRFZ）隔离，该断裂带是许多苏铁物种的生物地理屏障。在这项研究中，我们研究了C. bifida和C. micholitzii的分歧、遗传多样性、遗传结构和种群历史，以揭示这两种濒临灭绝物种的物种形成机制。结果显示，这两个物种之间的历史基因流较高，但当代基因流较低，在中新世晚期出现了深刻的分歧。长期的地理隔离和生态位分化被认为是驱动两个物种分化的重要因素，并得到了距离测试、屏障分析和生态位一致性检测的显着隔离的支持。RRFZ 的地理隔离通过限制基因流动而在促进其分化方面发挥了关键作用。保护遗传分析表明，两个物种内都有很高的遗传多样性，加上对更新世气候波动的不同反应：C. micholitzii经历了种群扩张，而C. bifida显示出轻微的瓶颈效应。为了确保两个受威胁物种的保护和长期可持续性，在评估其遗传多样性和结构的基础上，提出了相关的保护指南。这项研究为物种分化的机制提供了宝贵的见解，并为苏铁保护提供了可行的建议。

更新日期：2023-12-07

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