J Syst Evol

• Research Articles •    

Mitochondrial genes from eighteen angiosperms fill sampling gaps for phylogenomic inferences of the early diversification of flowering plants

Jia-Yu Xue1,2,3, Shanshan Dong4, Ming-Qiang Wang1, Tian-Qiang Song5, Guang-Can Zhou1,6, Zhen Li3, Yves Van de Peer3,7, Zhu-Qing Shao5, Wei Wang8, Min Chen1, Yan-Mei Zhang1, Xiao-Qin Sun1, Hongfeng Chen9, Yong-Xia Zhang10, Shou-Zhou Zhang4, Fei Chen11, Liangsheng Zhang11, Cymon Cox12, Yang Liu4,*, Qiang Wang5,*, Yue-Yu Hang1,*   

  1. 1Center for Plant Diversity and Systematics, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China

    2College of Horticulture, Nanjing Agricultural University, Nanjing, China

    3VIB-UGent Center for Plant Systems Biology and Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium.

    4Fairy Lake Botanical Garden, Shenzhen & Chinese Academy of Sciences, Shenzhen 518004, Guangdong, China

    5State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, 210046, China

    6College of Agricultural and Biological Engineering (College of Tree Peony), Heze University, Heze 274015, Shandong, China

    7Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0028, South Africa

    8State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, the Chinese Academy of Sciences, Beijing 100093, China

    9South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China

    10College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, Guangdong 518060, China

    11State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

    12Centro de Ciências do Mar, Universidade do Algarve, Faro, Portugal.

  • Received:2020-03-15 Accepted:2020-11-16

Abstract: The early diversification of angiosperms is thought to have been a rapid process, which may complicate phylogenetic analyses of early angiosperm relationships. Plastid and nuclear phylogenomic studies have raised several conflicting hypotheses regarding overall angiosperm phylogeny, but mitochondrial genomes have been largely ignored as a relevant source of information. Here we sequenced mitochondrial genomes from 18 angiosperms to fill taxon-sampling gaps in Austrobaileyales, magnoliids, Chloranthales, Ceratophyllales, and major lineages of eudicots and monocots. We assembled a data matrix of 38 mitochondrial genes from 107 taxa to assess how well mitochondrial genomic data address current uncertainties in angiosperm relationships. Although we recovered conflicting phylogenies based on different datasets and analytical methods, we also observed congruence regarding deep relationships of several major angiosperm lineages: Chloranthales were always inferred to be the sister group of Ceratophyllales, Austrobaileyales to mesangiosperms, and the unplaced Dilleniales was consistently resolved as the sister to superasterids. Substitutional saturation, GC-compositional heterogeneity, and codon-usage bias are possible reasons for the noise/conflict that may impact phylogenetic reconstruction; and angiosperm mitochondrial genes may not be substantially affected by these factors. The third codon positions of the mitochondrial genes appear to contain more parsimony-informative sites than the first and second codon positions, and therefore produced better resolved phylogenetic relationships with generally strong support. The relationships among these major lineages remain incompletely resolved, perhaps as a result of the rapidity of early radiations. Nevertheless, data from mitochondrial genomes provides additional evidence and alternative hypotheses for exploring the early evolution and diversification of the angiosperms.

Key words: early angiosperm radiation, mitochondrial genome, phylogenomics, incongruence, systematic error