Phylogeography of Japanese horse chestnut (<Emphasis Type="Italic">Aesculus turbinata</Emphasis>) in the Japanese Archipelago based on chloroplast DNA haplotypes

Japanese horse chestnut (Aesculus turbinata: Hippocastanaceae) is one of the typical woody plants that grow in temperate riparian forests in the Japanese Archipelago. To analyze the phylogeography of this plant in the Japanese Archipelago, we determined cpDNA haplotypes for 337 samples from 55 populations covering the entire distribution range. Based on 1,313 bp of two spacers, we determined ten haplotypes that are distinguished from adjacent haplotypes by one or two steps. Most of the populations had a single haplotype, suggesting low diversity. Spatial analysis of molecular variance suggested three obvious phylogeographic structures in western Japan, where Japanese horse chestnut is scattered and isolated in mountainous areas. Conversely, no clear phylogeographic structure was observed from the northern to the southern limit of this species, including eastern Japan, where this plant is more common. Rare and private haplotypes were also found in southwestern Japan, where Japanese horse chestnuts are distributed sparsely. These findings imply that western Japan might have maintained a relatively large habitat for A. turbinata during the Quaternary climatic oscillations, while northerly regions could not.     

Chloroplast DNA phylogeography of Fagus crenata (Fagaceae) in Japan

 CpDNA variation in Japanese beech, Fagus crenata (Fagaceae), was studied in 45 populations distributed throughout the species' range. Two cpDNA regions were sequenced: the non-coding region between the trnL (UAA) 5′exon and trnF (GAA), and the trnK region (including matK). Thirteen distinct cpDNA haplotypes were recognized and each haplotype was found to be geographically structured. Two major clades (I and II+III) were revealed in phylogenetic analyses among the haplotypes using F. sylvatica as an outgroup. The haplotypes of Clade I were distributed mainly along the Japan Sea side of the Japanese Archipelago, while those of Clade II+III occurred chiefly along the Pacific Ocean side. Consequently, the distribution of the two major cpDNA clades suggests that there were two migration routes in the history of F. crenata; one along the Japan Sea and the other along the Pacific Ocean side of the Japanese Islands. Received March 19, 2001 Accepted November 22, 2001     

Distribution and molecular characterization of distinct Asian populations of Bemisia tabaci (Hemiptera: Aleyrodidae) in Japan

Bemisia tabaci (Gennadius) is considered to be the most economically important pest insect worldwide. The invasive variant, the Q biotype of B. tabaci was first identified in 2004, and has caused significant crop yield losses in Japan. The distribution and molecular characterization of the different biotypes of B. tabaci in Japan have been little investigated. In this study, B. tabaci populations were sampled from the Japanese Archipelago, the Amami Archipelago and the Ryukyu Islands between 2004 and 2008, and the nucleotide sequences of their mitochondrial cytochrome oxidase I genes were determined. Bayesian phylogenetic relationship analysis provided the first molecular evidence that the indigenous Japanese populations could be separated into four distinct genetic groups. One major native population from the Japanese Archipelago, given the genetic group name Lonicera japonica, was separated into an independent group, distinct from the other genetic groups. The second major population, the Nauru biotype in the Asia II genetic group, was identified in the Amami Archipelago and the Ryukyu Islands. Two distinct minor genetic groups, the Asia I and the China, were also identified. One invasive B‐related population belonging to the Mediterranean/Asia Minor/Africa genetic group has been identified in Honshu. All lineages generated by the phylogenetic analyses were supported by high posterior probabilities. These distinct indigenous B. tabaci populations developed in Japan under geographical and/or biological isolation, prior to recent invasions of the B and Q biotypes.     

Multiple introduction events and artificial long-distance dispersal of the exotic slug Ambigolimax valentianus in Japan

ABSTRACT

The three-band garden slug Ambigolimax valentianus, native to the Iberian Peninsula, is an exotic species distributed worldwide and was introduced to Japan into the 1950s. For control of this slug, it is necessary to elucidate its introduction sources and dispersal patterns since the introduction event occurred. However, knowledge about this slug in Japan remains poor. Thus, we attempted to estimate the origin and dispersal patterns of this slug using genetic approaches. We investigated the genetic diversity of the mitochondrial cytochrome c oxidase subunit I gene across 11 populations of A. valentianus in three prefectures in central Japan. Ten haplotypes were found in the Japanese populations, five of which were haplotypes found in foreign individuals. The same haplotypes were found in all three prefectures, whereas the average haplotype diversity was high across all populations. Significant genetic differentiation was detected among 22 of 55 population pairs, but there was no isolation by distance. These molecular results suggest that multiple introductions to Japan may have occurred in the past such that the founder effect in the early stage of introduction was diluted. Furthermore, long-distance dispersal of A. valentianus would have occurred after introduction into Japan because of human activities rather than natural dispersal.     

Chloroplast DNA phylogeography of the endangered Japanese red maple (Acer pycnanthum): the spatial configuration of wetlands shapes genetic diversity

Aim Japanese red maple (Acer pycnanthum K. Koch) is an endangered species which grows in discrete wetland ecosystems within a limited geographical range. It is an important relic of geologic time, an endemic of unique wetland ecosystems and an indicator of hotspots of plant species diversity. However, information on its genetic characteristics across its range is lacking. Our aim was to determine the genetic structure and diversity of the species and make recommendations for conservation. Location Wetlands in central Honshu Island, Japan. Methods We collected leaf samples from 400 individuals of A. pycnanthum in 30 populations, extracted total DNA from each and sequenced three non‐coding regions of chloroplast DNA. Results We identified nine haplotypes. High haplotype diversity (0.81) and the occurrence of rare haplotypes in eight distant populations suggest that wetlands provided multiple, adequate‐size refuges during the Last Glacial Maximum. We found only one to four haplotypes within populations. The high degree of differentiation (G_ST = 0.83) implies that gene flow by seeds among populations is restricted. Eight populations demonstrated a positive contribution to the total genetic diversity owing to occurrence of rare and private haplotypes. Such populations are concentrated in the south‐western part of the species distribution. According to the spatial autocorrelation analysis, there were significant spatial clusters of populations, which were characterized by similar haplotype composition. Using the haplotype distribution, samova and barrier detected nearly identical genetic boundaries. Main conclusion In spite of the species’ limited geographical range, we identified a relatively high number of haplotypes and a clear geographical structure. We propose six management units, which can be used for future conservation activities, such as introduction of new individuals for on‐site conservation projects and seed collection for ex situ conservation.     

Phylogeography of Ophiorrhiza japonica (Rubiaceae) in continental islands,the Ryukyu Archipelago,Japan

Aim Phylogeographical patterns in the Ryukyu Archipelago have been explained primarily by landbridge formation and the opening of two straits in the Pliocene, namely the Tokara and Kerama gaps. These old straits have been considered to be the barriers most likely to determine genetic boundaries. To test this, we conducted a molecular analysis of the herb Ophiorrhiza japonica. We discuss the causes of and processes involved in its phylogeographical structure and explore aspects of island separation other than the duration of the straits to explain genetic boundaries at the gaps. Location Ryukyu Archipelago, Japan. Methods Plants were collected from 40 localities in the archipelago and vicinity. Non‐coding regions of chloroplast DNA were sequenced. The genealogical relationships among haplotypes were estimated using a statistical parsimony network. To examine the phylogeographical structure, we compared two parameters of population differentiation, namely G_ST and N_ST, and conducted correlation analysis of genetic and geographical distances. Genetic boundaries were identified using Monmonier’s maximum difference algorithm. To test vicariance–dispersal hypotheses, that is, vicariance after migration via the Pliocene landbridge or over‐sea dispersal in the Pleistocene, molecular dating analysis was conducted. Results A statistical parsimony network revealed that the haplotypes from the Ryukyu Archipelago and northwards coalesce to one ancestral haplotype in Taiwan. A clear phylogeographical structure was observed: plants within the same population and populations in geographical proximity were phylogenetically close. A genetic boundary was recognized across the Kerama Gap, but not across the Tokara Gap. Dating analysis suggested that population divergence across the Kerama Gap occurred in the early to late Pleistocene. Main conclusions The statistical parsimony network suggests migration from Taiwan and northward range expansion in the archipelago. Based on the divergence time, over‐sea dispersal in the Pleistocene is likely, although migration via a Pliocene landbridge is not totally rejected. Negligible genetic differentiation across the Tokara Gap suggests recent over‐sea dispersal, possibly facilitated by the small geographical width of the gap. Conversely, the large genetic differentiation across the Kerama Gap is probably explained by the large geographical distance across it. The past splitting of a landbridge would have had a significant influence on population differentiation after a certain geographical distance was reached.     

Genetic differentiation among populations ofArabis serrata (Brassicaceae) along its geographic distribution

Levels and distribution of genetic variation were investigated in ten populations of the perennialArabis serrata distributed along a latitudinal gradient throughout Japan. Populations of this endemic species occupy predominantly three types of habitats: limestone and derived soils, volcanic and disturbed sites. Previous studies showed that plants ofA. serrata are differentiated in morphological and ecological traits under both natural conditions and common garden experiments suggesting genetic differentiation among populations. To assess the degree of genetic differentiation under different habitats ofA. serrata populations, we analyzed the isozyme genetic structure. Ten populations, located in mountains of central and northern Honshu and Hokkaido, were analyzed by starch gel enzyme electrophoresis. Fourteen loci of eight enzymes were resolved and six loci were monomorphic for all the populations. Populations sampled maintain low levels of genetic variation (P=0.16;H=0.05;A=1.16) compared to that maintained by other outcrossing seed plants. In some cases, few or no heterozygous individuals were detected, and consequently, mean observed heterozygosity was zero or near zero. Six (29%) of the fixation indices,F, estimated deviated significantly from Hardy Weinberg genotypic expectations indicating a deficiency of heterozygotes in most of the cases. The mean genetic identity (Nei'sI) between population pairs was 0.852 and indicates a moderate level of genetic differentiation among populations.Arabis serrata has most of its genetic variation distributed among rather than within populations. The among-population component of the total genetic diversity (G _ST mean value) was 0.416, indicating genetic differentiation between populations. There groups of populations were recognized in an unrooted tree generated by the Neighbor-Joining method. These results suggest groups of populations differentiated regionally. Estimates of interpopulational gene flow (Nm) were very variable (range 0.049–3.718) with a meanNm=1.203 for all populations.     

Phylogeography of the endangered tideland snail Batillaria zonalis in the Japanese and Ryukyu Islands

The phylogeography of the endangered tideland snail Batillaria zonalis in the Japanese and Ryukyu Islands was analyzed on the basis of nucleotide sequences of a mitochondrial gene for cytochrome oxidase c subunit I (COI). Extremely low genetic diversity was found in populations at both the northern and southern boundaries of the geographic distribution of this species in Japan, i.e., Sendai Bay and Iriomotejima Island, respectively, which might be attributed to the population bottleneck due to historical environmental variations and/or the recent foundation of populations in the marginal part of the inhabitable range. Most populations contained unique rare haplotypes, and significant genetic differentiation on the whole was shown, while no clear geographic genetic structure was detected between the Japanese and Ryukyu Islands or over the distribution area of B. zonalis in Japan, with the exception of significant genetic divergences in Ago Bay in the central part of Honshu and the southern part of Okinawajima Island.     

Contact zone of two different chloroplast lineages and genetic guidelines for seed transfer in Quercus serrata and Quercus crispula

Within their natural distribution ranges, plant species exhibit a genetic structure that has been created by global climate change and natural selection over long periods. This genetic structure needs to be conserved for sustainable use of genetic resources. To conserve local forests with different genetic structures, genetic guidelines for seed and seedling transfer in individual species are necessary. Genetic guidelines have been published for 43 Japanese tree species using population genetic data; however, for practical use, more detailed genetic borders between important genetic lineages should be clarified to inform seed collection and planting. Thus, we investigated in detail the genetic borders between two important Japanese oak species, Quercus serrata and Quercus crispula, in the Chubu region of Japan using chloroplast and nuclear DNA markers, and we discuss the factors that influenced border creation using the results of species distribution modeling (SDM). The chloroplast DNA (cpDNA) haplotype was clearly different within the Chubu region of Japan but the difference in nuclear DNA between northern and southern haplotype populations was very small, both in Q. serrata and Q. crispula. The results of SDM showed that during the last glacial maximum (LGM) Q. serrata was distributed mostly along the coastline but Q. crispula was distributed not only along the coast but also in mountainous areas further inland. The cpDNA genetic borders of these two oak species are complex and seem to have been influenced by topography and their distribution during the LGM. We propose and discuss genetic guidelines for these two oak species based on the results of this study.     

Phylogeography of Arcterica nana (Ericaceae) suggests another range expansion history of Japanese alpine plants

We conducted a phylogeographic study on the alpine plant Arcterica nana based on haplotypes of chloroplast DNA. Using a sequence of approximately 1,071 bp of intergenic spacers of chloroplast DNA (trnT-L, psbB–psbF), we detected 13 haplotypes among 193 individuals sampled from 22 populations. Two dominant haplotypes were distributed over the entire range of this species in Japan, and we found several local private haplotypes. An analysis of molecular variance (AMOVA) indicated no geographic structure within the haplotype distribution. In addition, the genetic distance was not related to its corresponding geographic distance (Mantel test: r=−0.049, P=0.66), indicating a homogeneous geographic structure throughout the entire distribution range in the Japanese archipelago. The most parsimonious explanation for this geographic structure is that A. nana spread across its extant distribution range in the Japanese archipelago through a recent range expansion event. However, this pattern is inconsistent with the previous phylogeography of Japanese alpine plants, which reveals that haplotypes in central Honshu are differentiated from those in more northern regions. Arcterica nana may have experienced a different history from other alpine plants, suggesting that the history of Japanese alpine flora may include at least two different geographic radiation patterns.     

DNA barcoding reveals 24 distinct lineages as cryptic bird species candidates in and around the Japanese Archipelago

DNA barcoding using a partial region (648 bp) of the cytochrome c oxidase I (COI) gene is a powerful tool for species identification and has revealed many cryptic species in various animal taxa. In birds, cryptic species are likely to occur in insular regions like the Japanese Archipelago due to the prevention of gene flow by sea barriers. Using COI sequences of 234 of the 251 Japanese‐breeding bird species, we established a DNA barcoding library for species identification and estimated the number of cryptic species candidates. A total of 226 species (96.6%) had unique COI sequences with large genetic divergence among the closest species based on neighbour‐joining clusters, genetic distance criterion and diagnostic substitutions. Eleven cryptic species candidates were detected, with distinct intraspecific deep genetic divergences, nine lineages of which were geographically separated by islands and straits within the Japanese Archipelago. To identify Japan‐specific cryptic species from trans‐Paleartic birds, we investigated the genetic structure of 142 shared species over an extended region covering Japan and Eurasia; 19 of these species formed two or more clades with high bootstrap values. Excluding six duplicated species from the total of 11 species within the Japanese Archipelago and 19 trans‐Paleartic species, we identified 24 species that were cryptic species candidates within and surrounding the Japanese Archipelago. Repeated sea level changes during the glacial and interglacial periods may be responsible for the deep genetic divergences of Japanese birds in this insular region, which has led to inconsistencies in traditional taxonomies based on morphology.     

Phylogeographic analysis of the brown alga Cutleria multifida (Tilopteridales,Phaeophyceae) suggests a complicated introduction history

In depth genetic comparisons of populations of Cutleria multifida (Tilopteridales, Phaeophyceae) collected from Europe, the northwestern Pacific Ocean, Australia and New Zealand using the DNA sequences of four gene regions (the mitochondrial cox2 and cox3 genes, the intergeneric spacer region adjacent to cox3, and the open reading frame) suggested that the northwestern European and Japanese populations were considerably greater in terms of their genetic divergence than Mediterranean, Australian or New Zealand populations. The haplotypes of the populations in northwestern European (distribution range including the type locality, seven haplotypes) and Japanese populations (seven haplotypes) were unique except for one shared haplotype. There were weak but positive correlations between the geographical distance and the genetic divergence among northwestern European and Japanese populations. Moreover, both female and male gametophytes occurred in eight of the nine Japanese localities, suggesting Japanese populations showed normal sexual heteromorphic life history of the species. In light of these results, it appears that Japanese populations were native to the area despite earlier hypothesis. In contrast, Australian and New Zealand populations were composed of only one haplotype that is very close to those found in northwestern Europe and Japan, suggesting a recent introduction history from Europe (or from northeastern Asia via Europe) by ship transport to Australia and New Zealand. The Mediterranean populations included two haplotypes identical to those found in northwestern Europe and Japan, and it is suggestive of transoceanic introductions of some populations between Mediterranean and Japanese coasts.     

Population fragmentation causes randomly fixed genotypes in populations of <Emphasis Type="Italic">Arabidopsis kamchatica</Emphasis> in the Japanese Archipelago

Populations of arctic alpine plants likely disappeared and re-colonised several times at the southern edge of their distributions during glacial and interglacial cycles throughout the Quaternary. Range shift and population fragmentation after a glacial period would affect the genetic structure of such plants in southernmost populations. We aimed to elucidate how climatic oscillations influenced the population subsistence of alpine plants in the Japanese Archipelago as one of the southernmost populations, by inferring the genetic structure of Arabidopsis kamchatica subsp. kamchatica and the intraspecific littoral taxon, subsp. kawasakiana. We identified genotypes based on the haplotypes of five nuclear genes and two chloroplast DNA spacers for 164 individuals from 24 populations. Most populations harboured only one private genotype, whereas few polymorphisms were found in each population. Two genetic genealogies were found, suggesting that northern Japanese populations of alpine subsp. kamchatica, subsp. kawasakiana and the northerly subsp. kamchatica in eastern Russia and Alaska clustered and differentiated from populations in central Honshu, western Japan and Taiwan. During climatic oscillations, the genetic structure of extant southernmost populations would have been shaped by strong genetic drift under population fragmentation and randomly fixed to a single genotype among their ancestral polymorphisms.     

Phylogeography of the leaf beetle Chrysolina virgata in wetlands of Japan inferred from the distribution of mitochondrial haplotypes

The genetic differentiation among populations of the leaf beetle Chrysolina virgata living in wetlands of Japan was studied based on the sequence data of the mitochondrial cytochrome oxidase subunit I gene region (750 bp). Two distinct lineages of mitochondrial haplotypes were found: one (clade A) consisted of 26 haplotypes distributed over the distribution range of C. virgata between north‐east Honshu and Kyushu, whereas the other (clade B) was monotypic and confined to a small region in north‐east Honshu where it coexisted with clade A. Nested clade analysis for these haplotypes suggested that range expansion and following differentiation due to isolation by distance might have resulted in the present distribution pattern of the haplotypes in clade A. We discuss the evolutionary process leading to the occurrence of two distinct haplotype clades in Japan in terms of repeated colonization from the continent and range expansion and contraction during climatic changes.     

Phylogeography of Asparagopsis taxiformis revisited: Combined mtDNA data provide novel insights into population structure in Japan

Six intraspecific lineages (Lineages 1–6) of Asparagopsis taxiformis have been previously established based on mitochondrial cox2‐cox3 intergenic spacer and a partial cox1 sequences. ‘Lineage 2’ (L2) was suggested to be a recent introduction to the Mediterranean Sea, but its source population has not yet been identified. In order to clarify the nature of northwestern Pacific populations, we performed extensive sampling in Japan (60 individuals from 16 locations) and molecular phylogenetic analyses based on mitochondrial sequences. Sixteen additional individuals, collected from eight locations in the Indo‐Pacific, Caribbean, and Mediterranean regions, were also analyzed. Combined sequence analyses revealed that the Japanese populations only consisted of L2. Out of 19 combined haplotypes identified within L2, two are shared between Japan and the Mediterranean Sea and the Hawaiian Islands, and 12 were identified as endemic to Japan. Genetic analyses of population differentiation suggested that Japanese populations are genetically isolated from the Mediterranean and the Hawaiian populations. A genetic disjunction appears to separate two subpopulations within Japan: one between Toi and Kagoshima and the other between Ojikajima Island and Kagoshima in the Kyushu area.     

Intraspecific sequence variation of chloroplast DNA inPedicularis chamissonis Steven (Scrophulariaceae) and geographic structuring of the Japanese “Alpine” plants

In order to clarify evolutionary patterns and processes of intraspecific diversification ofPedicularis chamissonis Steven, we analyzed intraspecific variation of the nucleotide sequences of non-coding regions of chloroplast DNA: the intergenic spacers betweentrnT (UGU) andtrnL (UAA) 5′exon,trnL (UAA) 3′exon andtrnF (GAA), andatpB andrbcL. In 24 populations ofP. chamissonis, 33 nucleotide substitutions and 12 insertions/deletions were inferred, and their genetic distances ranged from 0.001 to 0.014. Seventeen distinct cpDNA haplotypes could be recognized and each haplotype was found to be geographically structured. Two major clades (the Northern and Southern clades) were revealed in phylogenetic analyses of cpDNA haplotypes. The haplotypes of the Northern clade had a wider distribution area in the populations of Mts. lide of central Honshu in Japan, northward to Unalaska Island in the Aleutians. Relationships among most haplotypes were unresolved polytomies. On the other hand, the haplotypes of the Southern clade occurred from the populations of Mt. Gassan southwards to Mt. Arakawa of central Honshu. Within this clade, three subclades were clearly recognized. From these results, we concluded that the haplotypes of the Northern and Southern clades inP. chamissonis might have traveled down to Japanese Archipelago from the north in not a single glacial period.     

Phylogeographical structure in Zelkova serrata in Japan and phylogeny in the genus Zelkova using the polymorphisms of chloroplast DNA

The genetic differentiation inherent in Zelkova serrata in Japan and the southern portion of the Korean Peninsula was examined by comparing a chloroplast DNA (cpDNA) sequence over a 16?k baselength in 40 individual samples collected from an area covering the natural distribution range of Z. serrata in Japan and the southern portion of the Korean Peninsula. We detected over 50 single-nucleotide polymorphisms in the protein-coding and intergenic regions, and over 30 insertions/deletions in the intergenic region. From the polymorphisms detected in the cpDNA, 14 haplotypes were identified. These 14 haplotypes had cluster-like structures and genetic differentiation between the clusters was large. Closely related haplotypes existed in adjacent regions. One haplotype existed in both Japan and the Korean Peninsula. By comparison with other Zelkova species, Z. serrata is apparently distinct from European and East Asian Zelkova species and Z. serrata is closest to the Ulmus species in the genus Zelkova. The effects of the analyzed length of the cpDNA sequence on the detection of polymorphisms were analyzed by re-sampling simulation.     

Amphibian chytridiomycosis in Japan: distribution,haplotypes and possible route of entry into Japan

A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes and 2103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that three of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host‐specific distribution of the fungus.     

PHYLOGEOGRAPHY OF CUTLERIA CYLINDRICA (CUTLERIALES,PHAEOPHYCEAE) IN NORTHEASTERN ASIA,AND THE IDENTITY OF AN INTRODUCED POPULATION IN CALIFORNIA1

Cutleria cylindrica Okamura was described from Japan in 1902 and has been reported only from northwestern Asia until its relatively recent discovery in California, USA, and Baja California, Mexico. To clarify the genetic relationships within and among the disjunct populations, we carried out a molecular phylogenetic study, as well as the examination of sex ratio and the life‐history patterns, of populations in Japan, Korea, and California. Based on the DNA sequences of mitochondrial genes cox2, cox3, the open reading frame (ORF) region, and the spacer between cox3 and ORF, a total of 23 haplotypes were detected in the 85 individuals from 20 localities in Japan, Korea, and California. All localities in Japan and Korea included multiple haplotypes, but only a single haplotype was found in California. There was a positive relationship between distance and genetic divergence in Japan and Korea. The single haplotype found in California was the same as one occurring in Japan (Aomori Pref. and Fukuoka Pref.) and Korea (Daedaepo, Pusan). Both male and female gametophytes were distributed in most northeastern Asian populations. Only female gametophytes, developing parthenogenetically from female gametes, were found in California and Aomori Pref., Japan. On the basis of these results, we conclude that the disjunct population of C. cylindrica in California originated from a relatively recent introduction from Japan and shares its origin with the parthenogenetic population in the Tsugaru Strait.     

Low genetic differentiation among populations ofArabis serrata (Brassicaceae) along an altitudinal gradient

We investigated the extent of genetic differentiation among populations of fujihatazao,Arabis serrata along an altitudinal gradient at Mt. Fuji in Shizuoka Prefecture. This species is a perennial plant, widely distributed in Japan forming small isolated populations. However, at Mt. Fuji, this species constitutes a large population distributed from 1440 to 2400 m altitude. A total of 411 individuals were sampled from ten subpopulations. Eighteen loci were detected on eleven enzyme systems. Eleven loci were monomorphic and seven loci were polymorphic with a mean of 2.11 alleles per loci. Nei's genetic distance (mean 0.01) and genetic identity (mean 0.968) were very similar among populations indicating a low genetic differentiation. The total genetic diversity (H _T ) estimated for the polymorphic loci was, in average, 0.396. The mean gene differentiation (G_ST=0.091) was very low. Gene frequency of seven polymorphic loci was analyzed by spatial autocorrelation methods based on Moran's indexes. Only Pgi-3 exhibited a significant negative autocorrelation (−0.160;P<0.05); other loci values ranged from −0.134 to 0.027. Gene flow estimated by indirect methods varied between genes but most of the values were high (meanNm=20.8) suggesting that subpopulations at different altitudes are probably connected. Despite plants at different altitudes present different ecological traits (e.g., differences in phenology, growth and reproductive traits), subpopulations ofA. serrata are still low differentiated, at least for the loci studied. This may be explained by the recent origin of some habitats (e.g., second crater and surrounded areas) in this locality.