R&D CENTER

Morphological, molecular phylogenetic, and genomic study in the progenitor and derivative species pairs of Pseudostellaria palibiniana and Pseudotellaria longipedicellata (Caryophyllaceae)

Jongsun Park*, Yongsung Kim, Hong Xi, and Seung-Chul Kim
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Pseudostellaria Pax (Caryophyllaceae) is a small genus with about 25 species and is distributed in temperate regions, primarily extending from Central Asia and Afghanistan to Korea and Japan. A single species is also known from southeastern Europe, while three species occur exclusively in western North America. Recently, a new endemic species, Pseudostellaria longipedicellata was described in Korea, of which morphology is clearly differentiated from its close relative P. palibiniana, especially for elongated pedicel toward the ground after flowering. With exception in certain areas of the Korean peninsula, the two species show allopatric distribution; P. palibiniana occurs widely in somewhat dry places near mountain summits in southwestern and northern part, whereas P. longipedicellata is narrowly restricted to east and west sides of the Taebaek Mountains. Phylogenetic analyses based on seven chloroplast markers and nuclear ITS sequences showed that the clade containing P. longipedicellata is not highly resolved its close relatives (i.e., P. palibinina, P. okamotoi and P. setulosa). Nevertheless, molecular phylogenetic analyses and morphology suggested that P. longipedicellata is most closely related to P. palibiniana, suggesting a progenitor and derivative species relationship. To further clarify morphological and genomic differences between the species pairs of P. longipedicellata and P. palibiniana, we sequenced and assembled the genome of two species. The de novo draft assembly of P. longipedicellata and P. palibiniana resulted in 1.25 Gbp (Max length is 2,945,605 bp and N50 is 10,144bp) and 1.29 Gbp (Max length is 70,167bp and N50 is 932bp; low coverage), respectively. Genome-wide alignment between the two genomes showed 61.5\% of P. palibinina genome are aligned against P. longipedicellata genome with 9.25 million SNPs and INDELs. This variation level is within the range of within a species or between species, suggesting the progenitor and derivative species relationship between them. Further comparative genomic analyses with additional genomes originated from multiple populations will shed new light into the genomic basis of species differences in the progenitor and derivative species pairs as well as the complex evolutionary history of recently diversified plant lineages in East Asia.