JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2024, Vol. 48 ›› Issue (4): 37-45.doi: 10.12302/j.issn.1000-2006.202406025

Special Issue: 专题报道Ⅰ:郑万钧先生诞辰120周年纪念专题Ⅱ

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Phylogenetic relationship and evolutionary patterns of Tsuga pollen morphology: a cluster analysis-based study

CHEN Zhihan1,3(), SHANG Xin1,2, XIE Zin2, ZHANG Xin1,*()   

  1. 1. College of Forestry, Northwest A&F University, Yangling 712100,China
    2. Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    3. Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
  • Received:2024-06-17 Revised:2024-07-10 Online:2024-07-30 Published:2024-08-05
  • Contact: ZHANG Xin E-mail:13657974778@163.com;xin.zhang@nwafu.edu.cn

Abstract:

【Objective】To analyze the phylogenetic relationships and evolutional patterns of pollen morphology in Tsuga, we observed and compared the pollen characteristics of all 10 extant species of Tsuga along with pollen fossils.【Method】Pollen morphology was examined using scanning electron microscopy (SEM), and hierarchical cluster analysis (HCA) was conducted using seven quantitative indicators and one qualitative indicator.【Result】Tsuga pollens typically exhibits characteristics of the N1P3C1 type, with a leptoma on the distal face. The equatorial length ranges from 21.20 to 58.00 μm, predominantly lacking sacci but occasionally with echinae saccate forms. The pollen surface is typically warty or sparsely micro-warty, with spines or without. According to the hierarchical cluster analysis, Tsuga could be divided into three categories: ①saccate but lacking echinae type: T. mertensiana and Nothotsuga longibracteata; ②lacking sacci and echinae type: T. caroliniana, T. canadensis and pollen fossil T. sp.2; ③lacking sacci but echinate type: T. heterophylla, T. ulleungensis, T. diversifolia, T. forrestii, T. sieboldii, T. dumosa, T. chinensis and pollen fossil T. sp.1, T. sp.3.【Conclusion】Pollen morphology in Tsuga has evolved from saccate to non-saccate forms, and from lacking spines to possessing spines. These pollen characteristics are closely related to geographic distribution, indicating similarity among pollen from the same regions. The clustering analysis based on pollen morphology largely aligns with molecular phylogenetic trees, offering a method to distinguish extant species and fossils of Tsuga and providing valuable insights for phylogenetic studies of Tsuga.

Key words: Tsuga, pollen morphology, scanning electron microscopy(SEM), cluster analysis

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