Crape myrtles are economically important ornamental trees of the genus Lagerstroemia L. (Lythraceae), with a distribution from tropical to northern temperate zones. They are positioned phylogenetically to a large subclade of rosids (in the eudicots) which contain more than 25% of all the angiosperms. They commonly bloom from summer till fall and are of significant value in city landscape and environmental protection. Morphological traits are shared inter-specifically among plants of Lagerstroemia to certain extent and are also influenced by environmental conditions and different developmental stages. Thus, classification of plants in Lagerstroemia at species and cultivar levels is still a challenging task. Chloroplast (cp) genome sequences have been proven to be an informative and valuable source of cp DNA markers for genetic diversity evaluation. In this study, the complete cp genomes of three Lagerstroemia species were newly sequenced, and three other published cp genome sequences of Lagerstroemia were retrieved for comparative analyses in order to obtain an upgraded understanding of the application value of genetic information from the cp genomes. The six cp genomes ranged from 152,049 bp (L. subcostata) to 152,526 bp (L. speciosa) in length. We analyzed nucleotide substitutions, insertions/deletions, and simple sequence repeats in the cp genomes, and discovered 12 relatively highly variable regions that will potentially provide plastid markers for further taxonomic, phylogenetic, and population genetics studies in Lagerstroemia. The phylogenetic relationships of the Lagerstroemia taxa inferred from the datasets from the cp genomes obtained high support, indicating that cp genome data may be useful in resolving relationships in this genus.

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Background Crape myrtles, belonging to the genus Lagerstroemia L., have beautiful paniculate inflorescences and are cultivated as important ornamental tree species for landscaping and gardening. However, the phylogenetic relationships within Lagerstroemia have remained unresolved likely caused by limited sampling and the insufficient number of informative sites used in previous studies. Results In this study, we sequenced 20 Lagerstroemia chloroplast genomes and combined with 15 existing chloroplast genomes from the genus to investigate the phylogenetic relationships and divergence times within Lagerstroemia. The phylogenetic results indicated that this genus is a monophyletic group containing four clades. Our dating analysis suggested that Lagerstroemia originated in the late Paleocene (~ 60 Ma) and started to diversify in the middle Miocene. The diversification of most species occurred during the Pleistocene. Four variable loci, trnD-trnY-trnE, rrn16-trnI, ndhF-rpl32-trnL and ycf1, were discovered in the Lagerstroemia chloroplast genomes. Conclusions The chloroplast genome information was successfully utilized for molecular characterization of diverse crape myrtle samples. Our results are valuable for the global genetic diversity assessment, conservation and utilization of Lagerstroemia.

Species composition, physiognomy, and plant diversity of the less known cloud forests in Yunnan were studied based on data collected from 35 sample plots at seven sites. In floristic composition, the cloud forests are mainly comprised of Fagaceae, Ericaceae, Vacciniaceae, Aceraceae, Magnoliaceae, Theaceae, Aquifoliaceae, Illiciaceae, Lauraceae, and Rosaceae. Physiognomically, the forests are dominated by tree and shrub species. Lianas are rare in the forests. The plants with microphyllous or nanophyllous leaves comprise 44.32-63.46% of the total species, and plants with an entire leaf margin account for more than 50% of the tree and shrub species. There are few tree and shrub species with a drip tip leaf apex and papery leaves. Evergreen species make up more than 75% of the total tree and shrub species. In a 2,500 m 2 sampling area, the number of vascular species ranged between 57 and 110; Simpson's diversity index ranged from 0.7719 to 0.9544, Shannon-Winner's diversity index from 1.8251 to 3.2905, and Pielou's evenness index from 0.5836 to 0.8982 for trees. The cloud forests in Yunnan are physiognomically similar to the tropical cloud forests in America and Southeast Asia. They very much resemble the mountain dwarf mossy forest in Hainan Island, southeastern China, and the Mountain ericaceous forests in the Malay Peninsula. The cloud forests in Yunnan are considered to be developed, as are the tropical upper montane cloud forests in Asia.