Inferring spatial patterns and drivers of population divergence of Neolitsea sericea (Lauraceae), based on molecular phylogeography and landscape genomics.

The relative roles of geography, climate and ecology in driving population divergence and (incipient) speciation has so far been largely neglected in studies addressing the evolution of East Asia's island flora. Here, we employed chloroplast and ribosomal DNA sequences and restriction site-associated DNA sequencing (RADseq) loci to investigate the phylogeography and drivers of population divergence of Neolitsea sericea. These data sets support the subdivision of N. sericea populations into the Southern and Northern lineages across the 'Tokara gap'. Two distinct sublineages were further identified for the Northern lineage of N. sericea from the RADseq data. RADseq was also used along with approximate Bayesian computation to show that the current distribution and differentiation of N. sericea populations resulted from a combination of relatively ancient migration and successive vicariant events that likely occurred during the mid to late Pleistocene. Landscape genomic analyses showed that, apart from geographic barriers, barrier, potentially local adaptation to different climatic conditions appears to be one of the major drivers for lineage diversification of N. sericea.