Genomic data resolve phylogenetic relationships of Australian mat-rushes, Lomandra (Asparagaceae: Lomandroideae)

Lomandra is the largest genus in Asparagaceae subfamily Lomandroideae and possesses economic, ecological, and ethnobotanical significance in Australia. Lomandra comprises four sections, L. section Capitatae, L. section Macrostachya, L. section Typhopsis and L. section Lomandra, the latter comprising series Lomandra and series Sparsiflorae, all recognized based solely on morphology. In this study, phylogenetic relationships were estimated for 79 Lomandroideae individuals, including 45 Lomandra species and subspecies (c. 63% of species and subspecies diversity). We generated genome-scale plastome sequence data and used maximum likelihood and Bayesian inference criteria for phylogenetic estimation. Lomandra was non-monophyletic, with Xerolirion divaricata nested within it. Two major clades were recovered: Capitatae-Macrostachya (CM) and Lomandra-Typhopsis (LT). The CM clade included a monophyletic Lomandra section Capitatae with a base chromosome number x = 7, and L. section Macrostachya (x = 8); the LT clade included L. sections Typhopsis and Lomandra, both x = 8. Section Lomandra series Lomandra and series Sparsiflorae were both recovered as non-monophyletic. Morphological characters were assessed to identify combinations of characters that characterize clades. A base chromosome number of x = 8 was plesiomorphic for Lomandra. The largest number of Lomandra species occupy the Mediterranean ecoregion and occupancy of sclerophyll vegetation was reconstructed as ancestral for the genus.