Phylogeny and Comparative Analysis for the Plastid Genomes of Five Tulipa (Liliaceae).

Species of Tulipa (Liliaceae) are of great horticultural importance and are distributed across Europe, North Africa, and Asia. The Tien Shan Mountain is one of the primary diversity centres of Tulipa, but the molecular studies of Tulipa species from this location are lacking. In our study, we assembled four Tulipa plastid genomes from the Tien Shan Mountains, T. altaica, T. iliensis, T. patens, and T. thianschanica, combined with the plastid genome of T. sylvestris to compare against other Liliaceae plastid genomes. We focussed on the species diversity and evolution of their plastid genomes. The five Tulipa plastid genomes proved highly similar in overall size (151,691-152,088 bp), structure, gene order, and content. With comparative analysis, we chose 7 mononucleotide SSRs from the Tulipa species that could be used in further population studies. Phylogenetic analyses based on 24 plastid genomes robustly supported the monophyly of Tulipa and the sister relationship between Tulipa and Amana, Erythronium. T. iliensis, T. thianschanica, and T. altaica were clustered together, and T. patens was clustered with T. sylvestris, with our results clearly demonstrating the relationships between these five Tulipa species. Our results provide a more comprehensive understanding of the phylogenomics and comparative genomics of Tulipa.

Insights into phylogeny, age and evolution of Allium (Amaryllidaceae) based on the whole plastome sequences.

BACKGROUND AND AIMS: The genus Allium L., one of the largest monocotyledonous genera and one that includes many economically important crops with nutritional and medicinal value, has been the focus of classification or phylogeny studies for centuries. Recent studies suggested that the genus can be divided into 15 subgenera and 72 sections, which were further classified into three evolutionary lineages. However, the phylogenetic relationships reconstructed by one or two loci showed weaker support, especially for the third evolutionary lineage, which might not show the species relationships very clearly and could hinder further adaptive and evolutionary study. METHODS: In this study, a total of 39 complete chloroplast genomes of Allium (covering 12 Allium subgenera) were collected, and combining these with 125 species of plastomes from 19 other families of monocots, we reconstructed the phylogeny of the genus Allium, estimated the origin and divergence time of the three evolutionary lineages and investigated the adaptive evolution in this genus and related families. RESULTS: Our phylogenetic analysis confirmed the monophyly and three evolutionary lineages of Allium, while new species relationships were detected within the third evolutionary lineage. The divergence time of the three evolutionary lineages was estimated to be in the early Eocene to the middle Miocene, and numerous positive selected genes (PSGs) and PSGs with high average Ka/Ks values were found in Allium species. CONCLUSIONS: Our results detected a well-supported phylogenetic relationship of Allium. The PSGs and PSGs with high Ka/Ks values, as well as diversified morphologies, complicated chromosome characteristics and unique reproductive modes may play important roles in the adaptation and evolution of Allium species. This is the first study that conducted phylogenetic and evolutionary analyses on the genus Allium combined with the plastome and morphological and cytological data. We hope that this study can contribute to further analysis of Allium for other researchers.