Intraspecific Karyotypic Polymorphism and Cytogeography of <i>Lysimachia mauritiana</i> (Primulaceae) on Several Islands in the Okinawa and the Daito Groups of the Ryukyu Archipelago, Japan

Abstract

Summary A coastal biennial herb, Lysimachia mauritiana, exhibited remarkable intraspecific karyotypic diversity, especially in the Ryukyu Archipelago of Japan (the Ryukyus). The species displayed five chromosome numbers (2n=16, 17, 18, 19, 20) and 18 cytotypes in the Ryukyus alone. Our serial investigations elucidated that: (1) 11 cytotypes on Takarajima Island (Is.) showed the highest intra-and inter-populational cytotype polymorphism in the Ryukyus, (2) a total of 15 cytotypes was recognized and several cytotypes coexisted in every locality on Amamioshima, Kakeromajima and Tokunoshima Is., and (3) closely located two Islands of Amamioshima and Tokunoshima had different dominant cytotypes, 16 (6m) and 18 (6m), respectively. In the present study, to explore whether a similar karyotypic polymorphism exists on their neighbor islands belonging to the Okinawa and the Daito Groups, a total of 610 plants from 51 localities on 10 islands were analyzed karyomorphologically and cytogeographically. As a result, five chromosome numbers (2n=16, 17, 18, 19, 20) and 13 cytotypes were recognized in the areas. Okinawajima Is. was divided into two areas according to cytotype distribution patterns. Northern and western areas facing the East China Sea showed intra-and inter-populational polymorphism in cytotype. By contrast, southern, eastern and northeastern areas facing the Pacific Ocean showed a single cytotype in a locality. In the Daito Group, 20 (4m) TS cytotype with a wide distribution in southern Taiwan was found in Japan for the first time. The cytotype probably descended from currents of southern Taiwan and/or the Philippines.

Intraspecific Karyotype Polymorphism and Chromosomal Evolution of <i>Lysimachia mauritiana</i> (Primulaceae) in the Ryukyu Archipelago of Japan and Taiwan

“…18 (6m), well represented on Tokunoshima Island is distrib-uted across about half the Amami G, and 18 (4m) (coral) in Okinawa Island covered more than half of the Okinawa G (Fig. 2 and Kono et al 2013Kono et al , 2015Kono et al , 2016. The 20 (4m) HD cytotype (magenta) is uniquely distributed around the northernmost point, Cape Hedo, on Okinawa Island.…”

“…The Satsunan G comprises three smaller islands Gs: Osumi, Tokara, and Amami; the Ryukyu G consists of two island sub-Gs: Okinawa and Sakishima. Our studies revealed that each island G and/or individual islands possess different dominant cytotypes, and display varied cytogeographical patterns at both inter-and intra-populational levels (Kono et al 2015(Kono et al , 2016.…”

“…Detailed information of collecting, pretreatment, fixation, staining, and chromosome observations for karyo-morphological and meiotic analyses have been described earlier (Oginuma et al 2004a, Kono et al 2012. Designations for marker chromosomes (m/st) and cytotype(s) were consistently applied in previous reports for the simplification of the wide-ranging karyotypic polymorphism of L. mauritiana (Oginuma et al 2004a, b, Kono et al 2008, 2010, 2012, 2013, 2015, 2016.…”

“…The single chromosome number, 2n=20 or n=10, has been reported for this species earlier (e.g., Chuang et al 1962, Carr 1978, Tanaka and Hizume 1978. However, over the last two decades, our serial studies elucidated a remarkable, wide-ranging intraspecific karyotype polymorphisms and complex cytogeographical structure throughout the Ryukyus and Taiwan: five chromosome numbers (2n=16, 17, 18, 19, 20) and 21 cytotypes in the Ryukyus (Oginuma et al 2004a, Kono et al 2008, 2010, 2013, 2015, 2016, and four chromosome numbers (2n=16, 18, 19, 20) and eight cytotypes in Taiwan (Oginuma et al 2004b, Kono et al 2012. Thus, these areas appear to be the center of intraspecific karyotype polymorphism of L. mauritiana.…”