COMPLEX PHYLOGENETIC PLACEMENT OF ILEX SPECIES (AQUIFOLIACEAE):

A CASE STUDY OF MOLECULAR PHYLOGENY

 

FAN YI^1,2, LE SUN^1,2, DA-CHENG HAO³, YONG PENG^1,2,* FENG-MING HAN^4,* AND PEI-GEN XIAO^1,2

 

¹Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Beijing 100193, China

²Key Laboratory of Bioactive Substances and Resources Utilization of Chinese Herbal Medicine,

Ministry of Education, Beijing 100193, China

³Biotechnology Institute, School of Environment and Chemical Engineering, Dalian Jiaotong University,

 Dalian 116028, China

⁴Beijing Biomarker Technologies Co., LTD, Beijing 101300, China

*Corresponding author’s email: ypeng@implad.ac.cn; fantasyee8991@163.com

 

Abstract

 To investigate the phylogenetic relationships among Ilex species distributed in China, we analyzed two alignments including 4,698 characters corresponding to six plastid sequences (matK, rbcL, atpB-rbcL, trnL-F, psbA-trnH, and rpl32-trnL) and 1,748 characters corresponding to two nuclear sequences (ITS and nepGS). Using different partitioning strategies and approaches (i.e., Bayesian inference, maximum likelihood, and maximum parsimony) for phylogeny reconstruction, different topologies and clade supports were determined. A total of 18 Ilex species was divided into two major groups (group I and II) in both plastid and nuclear phylogenies with some incongruences. Potential hybridization events may account, in part, for those phylogenetic uncertainties. The analyses, together with previously identified sequences, indicated that all 18 species were recovered within Eurasia or Asia/North America groups based on plastid data. Meanwhile, the species in group II in the nuclear phylogeny were placed in the Aquifolium clade, as inferred from traditional classification, whereas the species in group I belonged to several other clades. The divergence time of most of the 18 Ilex species was estimated to be not more than 10 million years ago. Based on the results of this study, we concluded that paleogeographical events and past climate changes during the same period might have played important roles in these diversifications.

 

Key words: Dating, Ilex, Molecular phylogeny, Phylogeography.