Asymmetric hybridization in Rhododendron agastum: a hybrid taxon comprising mainly F(1)s in Yunnan, China

Hong-Guang Zha, Richard I. Milne, Hang Sun

Research output: Contribution to journalArticlepeer-review

Abstract

Background and Aims Rhododendron (Ericaceae) is a large woody genus in which hybridization is thought to play an important role in evolution and speciation, particularly in the Sino-Himalaya region where many interfertile species often occur sympatrically. Rhododendron agastum, a putative hybrid species, occurs in China, western Yunnan Province, in mixed populations with R. irroratum and R. delavayi.

Methods Material of these taxa from two sites 400 km apart (ZhuJianYuan, ZJY and HuaDianBa, HDB) was examined using cpDNA and internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) loci, to test the possibility that R. agastumwas in fact a hybrid between two of the other species. Chloroplast trnL-F and trnS-trnG sequences together distinguished R. irroratumR. delavayiand some material of R. decorum, which is also considered a putative parent of R. agastum.

Key Results All 14 R. agastum plants from the HDB site had the delavayicpDNA haplotype, whereas at the ZJY site 17 R. agastum plants had this haplotype and four had the R. irroratum haplotype. R. irroratum and R. delavayi are distinguished by five unequivocal point mutations in their ITS sequences; every R. agastum accession had an additive pattern (double peaks) at each of these sites. Data from AFLP loci were acquired for between ten and 21 plants of each taxon from each site, and were analysed using a Bayesian approach implemented by the program NewHybrids. The program confirmed the identity of all accessions of R. delavayi, and all R. irroratum except one, which was probably a backcross. All R. agastum from HDB and 19 of 21 from ZJY were classified as F1hybrids; the other two could not be assigned a class.

Conclusions Rhododendron agastum represents populations of hybrids between R. irroratum and R. delavayi, which comprise mostly or only F1s, at the two sites examined. The sites differ in that at HDB there was no detected variation in cpDNA type or hybrid class, whereas at ZJY there was variation in both.

Original languageEnglish
Pages (from-to)89-100
Number of pages12
JournalAnnals of Botany
Volume105
Issue number1
DOIs
Publication statusPublished - Jan 2010

Keywords

  • F1-dominated hybrid zone
  • species barrier
  • habitat disturbance
  • Rhododendron agastum
  • R. irroratum
  • R. delavayi

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