J Syst Evol ›› 2020, Vol. 58 ›› Issue (6): 958-971.DOI: 10.1111/jse.12547

• Research Articles • Previous Articles     Next Articles

Phylogenetic relationships and biogeographic history of the unique Saxifraga sect. Irregulares (Saxifragaceae) from eastern Asia

Meng‐Hua Zhang1,2,3 , Chao‐Yong Wang1 , Cheng Zhang1 , Dai‐Gui Zhang1 , Ke‐Gang Li1 , Ze‐Long Nie1 , and Ying Meng1 *   

  1. 1 Key Laboratory of Plant Resources Conservation and Utilization, College of Biological Resources and Environmental Sciences, Jishou University, Jishou 416000, Hunan, China
    2 State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    3 College of Life Sciences, University of Chinese Academy of Science, Beijing 100049, China
  • Received:2019-02-26 Accepted:2019-10-21 Online:2019-10-23 Published:2020-11-01

Abstract:

Saxifraga L. is the largest genus in Saxifragaceae and a characteristic component of the herbaceous flora of the temperate and alpine mountains in the Northern Hemisphere. Section Irregulares is a small group of 15–20 species, representing one of the early‐diverged lineages in the genus characterized with unique zygomorphic flowers. We used both nuclear internal transcribed spacer and chloroplast DNA regions (psbA‐trnH, trnL‐F, and matK) to reconstruct its species relationships, estimate divergence times, and infer its historical biogeography. Our phylogenetic results corroborate the monophyly of sect. Irregulares and its sister relationship to sect. Heterisia from North America. The section was well resolved into two lineages corresponding to their morphological features and biogeographic distributions. One represents ser. Stoloniferae including S. stolonifera Curtis and S. nipponica Makino with long‐creeping stolons/rhizomes and small petals with spots and the other comprises the remaining taxa (ser. Rufescentes) which lack long‐creeping rhizomes. Spots on leaves (abaxially spotted vs. abaxially without spots) and spots on petals (without spots vs. with spots) are inferred to be phylogenetically informative within ser. Rufescentes. Divergence time estimates and ancestral area analysis suggested a western North American origin of sect. Irregulares with migration into East Asia by way of the Bering land bridge in the Middle Oligocene. The development of drying and desertification belt in the late Miocene could have played an important role in the subsequent restriction and separation of the north and south lineages within eastern Asia.

Key words: eastern Asia, historical biogeography, Saxifraga sect. Irregulares, Saxifragaceae