Effect of historical factors on genetic variation in the three terrestrial orchids <i></i>Cephalanthera erecta<i></i>, <i></i>Cephalanthera falcata<i></i>, and <i></i>Cephalanthera longibracteata<i></i> differing in breeding systems
3 April 2018
Chung, Mi Yoon; Lu, Nhan Thien ; López-Pujol, Jordi; Herrando-Moraira, Sonia; Chung, Jae Min; Tian, Huai Zhen; Suetsugu, Kenji; Kawahara, Takayuki; Yukawa, Tomohisa; Maki, Masayuki; Kumar , Pankaj ; Kim, Young-Dong; Chung, Myong GiPrevious studies have shown that levels of genetic diversity in species of the genus Cephalanthera vary depending on breeding systems. In the southern part of the Korean Peninsula, the three self-compatible, terrestrial orchids Cephalanthera erecta, C. falcata, and C. longibracteata flower synchronously in sympatric populations. The food-deceptive C. falcata, with bright yellow flowers, is predominantly outcrossing, whereas autogamy is the dominant strategy in both C. erecta and C. longibracteata, whose white flowers do not fully open. Given this, we expect that populations of C. falcata will harbor considerably higher levels of genetic variation than C. erecta and C. longibracteata. We examined genetic diversity (by means of allozymes) of the three species in sympatric populations (600 × 600-m area) in Yeonwhasan Provincial Park (YPP) and in non-sympatric populations outside YPP, South Korea. Thirteen out of 21 putative loci were variable across the three species, but unexpectedly we found a complete lack of allozyme variation within each species; in addition, the three species showed several diagnostic or unique alleles. Cephalanthera erecta and C. longibracteata are obligate autogamous species, with little chance to hybridize between them. Consistent with this, we did not detect allozyme-based hybrids within sympatric populations in YPP. Our results suggest that historical factors (i.e., the Quaternary climate oscillations) played a major role in determining levels of genetic diversity of the three Cephalanthera species. The Korean populations of C. erecta (a warm-temperate/temperate element) and C. falcata (a warm-temperate element) could have been established by a single introduction from a genetically depauperate ancestral population, likely located outside the Korean Peninsula. On the other hand, since C. longibracteata is a boreal/temperate element, it probably survived the Last Glacial Maximum in microrefugia located at low elevation regions within the Peninsula.