Comparative plastome genomics and phylogenetic analyses of Liliaceae

Abstract

Liliaceae, distributed mainly across the temperate Northern Hemisphere, are of great horticultural, culinary and medical importance, but are also a family with a long history of taxonomic uncertainty. Challenges in accurate species identification persist and phylogenetic relationships among genera in the family continue to be unresolved and/or weakly supported due to the use of limited molecular markers with insufficient variability. Here, nine newly sequenced plastomes for nine Liliaceae genera have been combined with previously published plastome data for this family, providing a total of 86 complete plastid genome sequences covering all 15 currently recognized genera for analyses. All these plastid genomes (146.9–158.3 kb) possess the typical quadripartite structure with conserved genome arrangement and content. Phylogenomic analyses strongly confirm the recognition of four subfamilies: Tricyrtidoideae with four genera; Medeoloideae with two genera; Lilioideae with eight genera and Calochortoideae, for Calochortus alone, as sister to Medeoloideae and Lilioideae. At least ten intergenic spacer regions that may serve as universal markers were identified in the family and, on a finer scale, nine and seven intergenic spacer regions are especially variable in Lilium and Fritillaria, respectively. The intergenic spacer regions rpoB-trnC, trnS-trnG, trnT-psbD and trnT-trnL, which showed high phylogenetic effectiveness, may be the best choices for future phylogenetic, phylogeographic and population genetic studies.