title: Intraspecific karyotypic polymorphism is highly concordant with allozyme variation in Lysimachia mauritiana (Primulaceae: Myrsinoideae) in Taiwan: implications for the colonization history and dispersal patterns of coastal plants.
abstract: OBJECTIVE
  Investigating intraspecific karyotypic and genetic variations jointly can provide unique insights into how historical, ecological and cytogenetic factors influence microevolution. A coastal herb, Lysimachia mauritiana, exhibits extensive karyotypic polymorphism and displays a complex cytogeographic pattern across the Ryukyus. To explore whether a similar degree of chromosomal variation exists south of the Ryukyus, and in an attempt to ascertain the mechanisms that may have generated the patterns, comprehensive sampling was conducted in Taiwan.
  
  
  METHODS
  Karyotypes were analysed at mitotic metaphase for 550 individuals from 42 populations throughout Taiwan Proper and its adjacent islands. In addition, genetic variation was estimated using 12 allozymes (21 loci) of 314 individuals sampled from 12 localities.
  
  
  RESULTS
  Four chromosome numbers and eight cytotypes, including four endemic cytotypes, were detected. Cytotype distributions were highly structured geographically, with single cytotypes present in most populations and four major cytotypes dominating the north, east and south of Taiwan and the Penghu Archipelago. Allozyme variation was very low and F-statistics indicated an extremely high level of population differentiation, implying limited gene flow among populations. Cluster analysis of allozyme variation uncovered four geographic groups, each corresponding perfectly to the four dominant cytotypes. The geographic structure of cytotype distribution and allozyme variation probably resulted from severe genetic drift triggered by genetic bottlenecks, suggesting that Taiwanese populations were likely to be derived from four independent founder events. In the few localities with multiple cytotypes, cytogeographic patterns and inferences of chromosomal evolution revealed a trend of northward dispersal, consistent with the course of the Kuroshio Current that has been influential in shaping the coastal biota of the region.
  
  
  CONCLUSIONS
  The data elucidate the patterns of colonization and the effects of the Kuroshio Current on the distribution of L. mauritiana in Taiwan. These inferences are highly relevant to other coastal plant species in the region and will stimulate further studies.
authors.affiliation: Herbarium (HAST), Biodiversity Research Center, Academia Sinica, Taipei 11529, Taiwan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Kono
authors.forename: Kuo-Fang
authors.initials: KF
authors.lastname: Chung
authors.forename: Chih-Hui
authors.initials: CH
authors.lastname: Chen
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Hoshi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Setoguchi
authors.forename: Chang-Hung
authors.initials: CH
authors.lastname: Chou
authors.forename: Kazuo
authors.initials: K
authors.lastname: Oginuma
authors.forename: Ching-I
authors.initials: CI
authors.lastname: Peng
mesh_terms: D005075:Biological Evolution; D032461:Chromosomes, Plant / Q000235:genetics; D056426:Genetic Loci / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D007527:Isoenzymes; D059785:Karyotype; D008540:Meiosis / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D010802:Phylogeny; D011110:Polymorphism, Genetic / Q000235:genetics*; D029623:Primulaceae / Q000201:enzymology / Q000235:genetics*; D013624:Taiwan
chemical_list: D007527:Isoenzymes