J Syst Evol

• Research Articles •    

Cryptic lineages and potential introgression in a mixed‐ploidy species (Phragmites australis) across temperate China

Le‐Le Liu1 , Mei‐Qi Yin1 , Xiao Guo2 , Jing‐Wen Wang1 , Yun‐Fei Cai3 , Cui Wang1 , Xiao‐Na Yu1 , Ning Du1 , Hans Brix4 , Franziska Eller4 , Carla Lambertini5 , and Wei‐Hua Guo1 *   

  1. 1 Institute of Ecology and Biodiversity, School of Life Sciences, Shandong University, Qingdao 266237, China
    2 College of Landscape Architecture and Forestry, Qingdao Agricultural University, Qingdao 266109, China
    3 School of Life Sciences, Qilu Normal University, Jinan 250013, China
    4 Department of Bioscience, Aarhus University, Aarhus 8000, Denmark
    5 Department of Agricultural and Food Sciences, University of Bologna, Bologna 40127, Italy
  • Received:2020-03-25 Accepted:2020-07-31 Online:2020-10-09

Abstract:

Polyploidization and hybridization are very common in natural plant species, and mixed‐ploidy species provide a unique opportunity to study the effects of evolutionary history, local abundance, and ploidy level on the direction and extent of introgression between intraspecific lineages. First, we delimited two morphologically cryptic lineages of Phragmites australis Trin. ex Steud. in temperate China using 11 nuclear microsatellites and two chloroplast DNA fragments with 225 samples from China as well as 11 samples from Oceania and Europe. Our evidence supported that haplotype O and haplotype P were two relatively independent lineages with low and high ploidy levels, respectively; haplotype M might be ancient and could have undergone a complex evolutionary history. Then we examined the lineage divergence and compared the introgression patterns between two major lineages along geographical and abundance gradients with a large number of samples (n = 1067) collected from China. The sympatric coexistence of two lineages in north and northeast China implies an ongoing or potential introgression between them. Cline analysis showed that the level of genetic admixture were significantly correlated with longitude rather than latitude. Our results also suggested that ploidy level could deeply influence the introgression asymmetry, and the effect of the current local abundance on introgression might be covered by the past coexistence time driven by phylogeographic history. Our study draws a baseline for future research on the ecological and evolutionary consequences of migration and introgression of Chinese P. australis under global change.

Key words: introgression, lineage divergence, Phragmites australis, ploidy level