Peering through the hedge: Multiple datasets yield insights into the phylogenetic relationships and incongruences in the tribe Lilieae (Liliaceae)

Abstract

The increasing use of genome-scale data has significantly facilitated phylogenetic analyses, contributing to the dissection of the underlying evolutionary mechanisms that shape phylogenetic incongruences, such as incomplete lineage sorting (ILS) and hybridization. Lilieae, a prominent member of the Liliaceae family, comprises four genera and approximately 260 species, representing 43% of all species within Liliaceae. They possess high ornamental, medicinal and edible values. Yet, no study has explored the validity of various genome-scale data in phylogenetic analyses within this tribe, nor have potential evolutionary mechanisms underlying its phylogenetic incongruences been investigated. Here, transcriptome, Angiosperms353, plastid and mitochondrial data, were collected from 50 to 93 samples of Lilieae, covering all four recognized genera. Multiple datasets were created and used for phylogenetic analyses based on concatenated and coalescent-based methods. Evolutionary rates of different datasets were calculated, and divergence times were estimated. Various approaches, including coalescence simulation, Quartet Sampling (QS), calculation of concordance factors (gCF and sCF), as well as MSCquartets and reticulate network inference, were carried out to infer the phylogenetic discordances and analyze their underlying mechanisms using a reduced 33-taxon dataset. Despite extensive phylogenetic discordances among gene trees, robust phylogenies were inferred from nuclear and plastid data compared to mitochondrial data, with lower synonymous substitution detected in mitochondrial genes than in nuclear and plastid genes. Significant ILS was detected across the phylogeny of Lilieae, with clear evidence of reticulate evolution identified. Divergence time estimation indicated that most of lineages in Lilieae diverged during a narrow time frame (ranging from 5.0 Ma to 10.0 Ma), consistent with the notion of rapid radiation evolution. Our results suggest that integrating transcriptomic and plastid data can serve as cost-effective and efficient tools for phylogenetic inference and evolutionary analysis within Lilieae, and Angiosperms353 data is also a favorable choice. Mitochondrial data are more suitable for phylogenetic analyses at higher taxonomic levels due to their stronger conservation and lower synonymous substitution rates. Significant phylogenetic incongruences detected in Lilieae were caused by both incomplete lineage sorting (ILS) and reticulate evolution, with hybridization and “ghost introgression” likely prevalent in the evolution of Lilieae species. Our findings provide new insights into the phylogeny of Lilieae, enhancing our understanding of the evolution of species in this tribe.