Large-scale phylogenomics reveals ancient introgression in Asian Hepatica and new insights into the origin of the insular endemic Hepatica maxima

Abstract

Hepatica maxima is native to Ulleungdo, which is one of the oceanic islands in Korea, and it likely originated via anagenetic speciation from the Korean mainland species H. asiatica. However, the relationships among the Asian lineages remain unresolved. Phylogenomics based on plant genomes can provide new insights into the evolutionary history of plants. We first generated plastid, mitochondrial and transcriptome sequences of the insular endemic species H. maxima. Using the genomic data for H. maxima, we obtained a phylogenomic dataset consisting of 76 plastid, 37 mitochondrial and 413 nuclear genes from Asian Hepatica and two outgroups. Coalescent- and concatenation-based methods revealed cytonuclear and organellar discordance in the lineage. The presence of gynodioecy with cytoplasmic male sterility in Asian Hepatica suggests that the discordance is correlated with potential disruption of linkage disequilibrium between the organellar genomes. Species network analyses revealed a deep history of hybridization and introgression in Asian Hepatica. We discovered that ancient and recent introgression events occurred throughout the evolutionary history of the insular endemic species H. maxima. The introgression may serve as an important source of genetic variation to facilitate adaptation to the Ulleungdo environment.