Chloroplast DNA insights into the phylogenetic position and anagenetic speciation of Phedimus takesimensis(Crassulaceae) on Ulleung and Dokdo Islands, Korea.

Seung-Chul Kim,Hee-Seung Seo,Lian-Ming Gao,Seon-Hee Kim

doi:10.1371/journal.pone.0239734

Abstract

Phedimus takesimensis (Ulleungdo flat-leaved stonecrop) is endemic to Ulleung and Dokdo Islands off the east coast of the Korean Peninsula. It was suggested that P. takesimensis originated via anagenetic speciation from the continental progenitor species P. kamtchaticus or P. aizoon. However, little is known of the phylogenetic relationships and population genetic structure among species of Phedimus in the Korean Peninsula and Ulleung/Dokdo Islands. We inferred the phylogenetic relationships among congeneric species in Korea based on nuclear ribosomal DNA internal transcribed spacer and chloroplast noncoding regions. We also sampled extensively for P. takesimensis on Ulleung Island and the continental species, P. kamtschaticus and P. aizoon, to assess the genetic consequences of anagenetic speciation. We found (1) the monophyly of P. takesimensis, (2) no apparent reduction in genetic diversity in anagenetically derived P. takesimensis compared to the continental progenitor species, (3) apparent population genetic structuring of P. takesimensis, and (4) two separate colonization events for the origin of the Dokdo Island population. This study contributes to our understanding of the genetic consequences of anagenetic speciation on Ulleung Island.

Highlights

The unique and diverse flora and fauna of the oceanic archipelagos are excellent model systems to investigate patterns and processes of evolution; oceanic islands are often considered as natural laboratories [1,2,3,4,5]
For P. latiovalifolius, which is endemic to Korea, we sampled a total of 10 accessions from Gangwon-do Province (Taebaek-si) and one accession from the same 15 populations sampled for the population genetic study for P. takesimensis (Table 1)
maximum likelihood (ML) analysis based on the nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) showed that Phedimus was strongly supported as a monophyletic group (100%) (Fig 3A)

Summary

Introduction

The unique and diverse flora and fauna of the oceanic archipelagos are excellent model systems to investigate patterns and processes of evolution; oceanic islands are often considered as natural laboratories [1,2,3,4,5]. Numerous insular endemic plant lineages with spectacular morphological, anatomical, and ecological diversity in the Pacific and Atlantic Oceans provide ample opportunities for naturalists to uncover their fascinating natural histories on islands Given the important role of anagenetic speciation ( known as phyletic or gradual speciation; see anacladogenesis, [22]) for explaining the origin of the majority of plant endemics, Ulleung Island has been recognized as an ideal place to investigate this particular mode of speciation among other oceanic archipelagos

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Results

Conclusion