J Syst Evol

• Research Article •    

Palynological and macroscopic characters evidence infer the evolutionary history and insight into pollination adaptation in Impatiens (Balsaminaceae)

Yong-Xiu Song1,2,3†, Tian Hu1,2†, Shuai Peng2,4,5, Yi-Yan Cong1*, and Guang-Wan Hu2,4,5*   

  1. 1 College of Life Sciences, Hunan Normal University, Changsha 410081, China
    2 CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture/Core Botanical Gardens, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan 430074, China
    3 College of Life Sciences, Sichuan University, Chengdu 610064, China
    4 Sino-Africa Joint Research Center, Chinese Academy of Sciences, Wuhan 430074, China
    5 University of Chinese Academy of Sciences, Beijing 100049, China
    Yong-Xiu Song and Tian Hu contributed equally to this work.
    *Authors for correspondence. Yi-Yan Cong. E-mail:congyiyan2004@aliyun.com;Guang-Wan Hu. E-mail:guangwanhu@wbgcas.cn
  • Received:2022-11-29 Accepted:2023-04-25 Online:2023-06-19

Abstract: The genus Impatiens comprises more than 1000 species and displays enormous morphological diversity. As a taxon that is notoriously difficult to classify morphologically, the taxonomic significance of pollen morphology has been discussed in previous studies. However, there was only limited study on the evolution of palynological and macroscopic character in this genus before. In this paper, we observed pollen of 143 species of Impatiens, including all representatives of infrageneric groups and discussed their taxonomic value. Meanwhile, based on the reconstructed phylogenetic framework, we selected five pollen traits, and nine macroscopic traits including both vegetative and reproductive organs for evolutionary analysis. The character reconstruction showed that the morphology and number of aperture, granules in lumina, seed number of per capsule, number of sepals, lateral united petals connate, spur length, and phyllotaxy could be identified as unambiguous, while other characters were ambiguous in the last common ancestor of Impatiens. The results of comprehensively macroscopic characters and palynological evidence suggest that these traits experienced a complicated evolution, exhibit high levels of instability and variability and occur character multiple reversals in the evolutionary processes of Impatiens due to different selection pressures. In addition, we found that there is an evident mosaic evolution in this genus. Pollen and macroscopic character are conserved with a slower evolutionary rate in the I. subgen. Clavicarpa, however, these characters showed higher diversity with a rapid rate of evolution in the I. subgen. Impatiens. Furthermore, the relationship between floral morphology and pollinators was discussed.

Key words: character evolution, Impatiens, palynology, pollination, taxonomy