Abstract
We analyzed variations in chloroplast DNA (cpDNA) in the widespread herbaceous species Hosta sieboldiana and Hosta albomarginata across large portions of their geographic ranges in the Japanese archipelago. Our objective was to compare the phylogeographic histories and phylogeographic structures of the two congeneric species in the Japanese archipelago. The location of the study is Japanese archipelago. We sequenced 1380 bp of noncoding cpDNA from 45 populations of H. sieboldiana (n = 362) and 55 populations of H. albomarginata (n = 436) to assess genetic variations within and among populations across almost the entire distributions of the species in Japan. Extant patterns of geographic structure were analyzed using statistical parsimony networks and spatial analysis of molecular variance (SAMOVA). We also used Monmonier's algorithm to detect genetic barriers between regions. Relationships between the populations were examined using a neighbor-joining (NJ) method. Four haplotypes were found for H. sieboldiana, whereas eight haplotypes were identified for H. albomarginata. Total genetic haplotype diversity (hT) and within-population haplotype diversity (hS) for H. sieboldiana were 0.352 and 0.040, respectively, while the values for H. albomarginata were 0.529 and 0.085, respectively. The population differentiations (GST) for H. sieboldiana and H. albomarginata were 0.839 and 0.886, respectively. The SAMOVA analysis revealed two clusters in H. sieboldiana and four clusters in H. albomarginata. Differentiations between and among the clusters were supported by the BARRIER analysis and the NJ tree. We detected differences in the population genetic structure between the two species. We found that H. sieboldiana had lower haplotype diversity than H. albomarginata. These results may be partially explained by the difference in ecological habitats and geographic distributions between the species. Hosta albomarginata is more widely distributed than H. sieboldiana in East Asia including Russia, and this large distribution range would enable more chances to intraspecific gene flow.
Highlights
Ecology and Evolution published by John Wiley & Sons Ltd
When indels were included in the sequencing data analyses, 16 haplotypes were found in a total of 362 individuals from 45 populations of H. sieboldiana, whereas 23 haplotypes were found in a total of 436 individuals from 55 populations of H. albomarginata (Table 2a,b)
The genetic relationships between the haplotypes of H. sieboldiana and H. albomarginata were revealed in the parsimony network (Fig. 3a,c)
Summary
The geographic distributions of intraspecific cpDNA variations have been examined in a variety of plant species to elucidate their postglacial migration history (Petit et al 2002; Mclachlan et al 2005; Ikeda et al 2009; Bai et al 2010; Kikuchi et al 2010; Lafontaine et al 2010; Chou et al 2011; Higashi et al 2012; Sede et al 2012; Cosacov et al 2013). A principal goal of comparative phylogeography is to infer biogeographic history from recurrent patterns in the geographic distribution of genetic variation in co-distributed species (Bermingham and Moritz 1998; Moritz and Faith 1998; Avise 2000). Comparative phylogeography of woody plants has been especially useful in reconstructing Quaternary forest distributions, in Europe and eastern North America (Palme et al 2003, 2004; Heuertz et al 2004; Grivet et al 2006; Maliouchenko et al 2007; Saeki et al 2011), and similar types of studies on Japanese plants have been performed on tree species (Okaura and Harada 2002; Kanno et al 2004; Okaura et al 2007; Iwasaki et al 2012) and alpine plants in temperate zones (Ohi et al 2003; Fujii and Senni 2006; Ikeda and Setoguchi 2006, 2007; Ikeda et al 2006, 2008a,b).
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