The diversity of chloroplast microsatellite loci in Siberian fir (Abies sibirica Ledeb.) and two Far East fir species A. nephrolepis (Trautv.) Maxim. and A. sachalinensis Fr. Schmidt

The genetic variability in 29 populations of Abies sibirica, three of A. nephrolepis, and seven of A. sachalinensis was studied using SSR markers of chloroplast DNA. Stable amplification and polymorphic products were obtained using primer pairs Pt71936 and Pt30204 (with nine and forteen alleles, respectively) of 10 pairs. Totally, 70 haplotypes were found, 43 in A. sibirica, 49 in A. sachalinensis, and 31 in A. nephrolepis. The highest values of genetic diversity parameters were observed in A. sachalinensis, and the lowest in A. nephrolepis. The Siberian fir differs from Far East species by the uneven multimodal frequency distributions of allele length in both cpSSR loci, which is explained by the presence of few separated from each other dominating haplotypes. This fact indicates that A. sibirica and the Far East species have different demographic histories. In A. sibirica, the proportion of diversity between populations in the total genetic diversity, calculated taking into account the differences between haplotypes (R(ST)) was 8.34% and 4.42% without accounting for haplotypes differences (R(ST) > G(ST), P= 0.01). The pairwise G(ST) correlate significantly with geographic distances between the populations A. sibirica and with genetic distances D calculated from allozyme data. No such correlations were found with the R(ST) parameter. The results of cpSSR variability analysis strongly support the conclusions inferred from allozyme data: several geographic groups of comparatively genetically close populations are identified, which may be explained by the invasion of colonization of the present-day Siberian fir range.     

Cytoplasmic composition in Pinus densata and population establishment of the diploid hybrid pine

Sequence and restriction site analyses of the paternally inherited chloroplast rbcL gene and maternally inherited mitochondrial nad1 fragments from the same set of populations and individuals were used to investigate cytoplasmic composition and population establishment of Pinus densata, a diploid pine that originated through hybridization between P. tabuliformis and P. yunnanensis. Two variable sites and three chlorotypes (TT, TC and GC) were detected on the rbcL gene of the three pines. P. densata harboured the three chlorotypes, two of which (TT, GC) were characteristic of the parental species, respectively. The third chlorotype (TC) was distributed extensively in seven of the 10 P. densata populations analysed, and might represent a mutation type or have been derived from an extinct parent. The distribution of chlorotypes, together with that of mitotypes, indicated that significant founder effect and backcross happened during the population establishment of the hybrid pine. P. tabuliformis and P. yunnanensis had acted as both mother and father donors, i.e. bi-directional gene flow existed between the two parental species in the past. Population differentiation of P. densata is high, as detected from the cytoplasmic genomes: GST = 0.533 for cpDNA and GST = 0.905 for mtDNA. The differences in cytoplasmic composition among the hybrid populations suggest that the local populations have undergone different evolutionary histories.     

DNA from bird-dispersed seed and wind-disseminated pollen provides insights into postglacial colonization and population genetic structure of whitebark pine (Pinus albicaulis)

Uniparentally inherited mitochondrial (mt)DNA and chloroplast (cp)DNA microsatellites (cpSSRs) were used to examine population genetic structure and biogeographic patterns of bird-dispersed seed and wind-disseminated pollen of whitebark pine (Pinus albicaulis Engelm.). Sampling was conducted from 41 populations throughout the range of the species. Analyses provide evidence for an ancestral haplotype and two derived mtDNA haplotypes with distinct regional distributions. An abrupt contact zone between mtDNA haplotypes in the Cascade Range suggests postglacial biogeographic movements. Among three cpSSR loci, 42 haplotypes were detected within 28 cpSSR sample populations that were aggregated into six regions. Analysis of molecular variance (amova) was used to determine the hierarchical genetic structure of cpSSRs. amova and population pairwise comparisons (FST ) of cpSSR, and geographical distribution of mtDNA haplotypes provide insights into historical changes in biogeography. The genetic data suggest that whitebark pine has been intimately tied to climatic change and associated glaciation, which has led to range movements facilitated by seed dispersal by Clark's nutcracker (Nucifraga columbiana Wilson). The two hypotheses proposed to explain the genetic structure are: (i) a northward expansion into Canada and the northern Cascades in the early Holocene; and (ii) historical gene flow between Idaho and the Oregon Cascades when more continuous habitat existed in Central Oregon during the late Pleistocene. Genetic structure and insights gained from historical seed movements provide a basis on which to develop recovery plans for a species that is at risk from multiple threats.     

A mitochondrial DNA minisatellite reveals the postglacial history of jack pine (Pinus banksiana), a broad-range North American conifer

Jack pine (Pinus banksiana Lamb.) is a broadly distributed North American conifer and its current range was covered by the Laurentian ice sheet during the last glacial maximum. To infer about the history and postglacial colonization of this boreal species, range-wide genetic variation was assessed using a new and highly variable minisatellite-like marker of the mitochondrial genome. Among the 543 trees analysed, 14 distinct haplotypes were detected, which corresponded to different repeat numbers of the 32-nucleotide minisatellite-like motif. Several haplotypes were rare with limited distribution, suggesting recent mutation events during the Holocene. At the population level, an average of 2.6 haplotypes and a mean haplotype diversity (H) of 0.328 were estimated. Population subdivision of genetic diversity was quite high with G(ST) and R(ST) values of 0.569 and 0.472, respectively. Spatial analyses identified three relatively homogeneous groups of populations presumably representative of genetically distinct glacial populations, one west and one east of the Appalachian Mountains in the United States and a third one presumably on the unglaciated northeastern coastal area in Canada. These results indicate the significant role of the northern part of the US Appalachian Mountains as a factor of vicariance during the ice age. A fourth distinct group of populations was observed in central Québec where the continental glacier retreated last. It included populations harbouring haplotypes present into the three previous groups, and it had higher level of haplotype diversity per population (H = 0.548) and lower population differentiation (G(ST) = 0.265), which indicates a zone of suture or secondary contact between the migration fronts of the three glacial populations. Introgression from Pinus contorta Dougl. var. latifolia Engelm. was apparent in one western population from Alberta. Altogether, these results indicate that the mitochondrial DNA variation of jack pine is geographically highly structured and it correlates well with large-scale patterns emerging from recent phylogeographical studies of other tree boreal species in North America.     

Organellar Inheritance in Liverworts: An Example of <Emphasis Type="Italic">Pellia borealis</Emphasis>

Liverwort Pellia borealis is an allopolyploid species that originated after the hybridization and chromosome doubling of two cryptic species; Pellia epiphylla species N and Pellia epiphylla species S. A sequence comparison of chloroplast tRNAUCCGly, tRNAUUULys gene introns, the mitochondrial tRNAGCUSer gene intron, and the first intron of the coxIII gene in the case of three liverwort species studied revealed that the chloroplast and mitochondrial sequences are identical in P. borealis and P. epiphylla species N but different from homologous P. epiphylla species S sequences. Both mitochondria and chloroplasts of P. borealis were thus inherited from one parent- P. epiphylla species N. Studies on 14 different populations of P. borealis gave the same result. These are the first data on organellar transmission in liverworts, the earliest land plants. Moreover, we show that the intron sequences of some organellar genes, until now not used in any systematic studies, could be very good markers in studying taxonomic relationships in closely related species and reconstructing historical events.     

Allozyme polymorphism of Swiss stone pine Pinus cembra L. in mountainous populations of the Alps and the Eastern Carpathians

Swiss stone pine Pinus cembra L. is a species with fragmented range, occurring in the Alpine-East Carpathian mountain system. Seeds of P. cembra are dispersed by nutcrackers, which offers potential possibilities for gene exchange among populations. Using isozyme analysis, we have examined five samples from two parts of the Swiss stone pine range: the Alps (Switzerland and Austria) and the Carpathians (two samples from the northern macroslope of the Gorgany Ridge, Eastern Carpathians, Ivano-Frankovsk oblast and one sample from Trans-Carpathian oblast of Ukraine). The allele frequencies of 30 isozyme loci, coding for enzymes ADH, FDH, FEST, GDH, GOT, IDH, LAP, MNR, MDH, PEPCA, 6PGD, PGI, PGM, SDH, SKDH, SOD, were analyzed using cluster analysis and methods of principal components. Two clusters, corresponding to the isolated Alpine and Carpathian parts of the range, were found. The main contribution to these differences were made by loci Adh-1, Adh-2, Fest-2, Lap-3, Mdh-4, and Sod-4. The interpopulation differentiation proved to be somewhat higher than that typical for pines (F(ST) = 7.4%), but within the limits characteristic for taxonomically close species. Thus, isolation of the populations did not lead to their marked differentiation, which may be explained by gene flow and balancing selection, which equalizes gene frequencies across the fragmented species area. Interlocus F(ST) heterogeneity (from 0.003 to 0.173) suggests adaptive significance of some of the allozyme polymorphisms or linkage of some loci with adaptive genes. The Carpathian populations were shown to have higher gene diversity than the Alpine ones (expected heterozygosities 0.095-0.114 and 0.060-0.080, respectively). A deficit of heterozygotes (as compared to the Hardy-Weinberg proportions), observed in the embryo sample, was probably explained by inbreeding. The reduction in the area of Carpathian pine forests in Holocene, caused by the global climatic changes and the anthropogenic impact, is hazardous for the gene pool of the species. The maintenance of genetic uniqueness of both Carpathian populations of P. cembra in general, and individual stands in particular, requires special measures for protection of Swiss stone pine in the Eastern Carpathians.     

Analysis of the genus Petagnaea Caruel (Apiaceae), using new molecular and literature data

In Southern Italy, an endemic monotypic genus belonging to family Apiaceae occurs: Petagnaea (P. gussonei), relict of Tertiary flora, belonging to subfamily Saniculoideae. At present, P. gussonei is an endangered species and is included in various lists of species deserving special protection. The genus belongs to scapose hemicryptophytes and shares a sciaphilous habitat (hygrophilous woodland). This study is aimed at doing a complete contribution about the evolutionary history of Petagnaea, using molecular markers as plastidial DNA (cpDNA), nuclear ribosomal DNA (rDNA) and data present in literature. We used nucleotide sequences from four regions of the chloroplast genome (rps16 intron, trnL^(UAA) intron, atpB-rbcL intergenic spacer, and partial matK gene) to investigate possible haplotypes in Petagnaea populations. To have an idea of the molecular relationships of all populations of P. gussonei, the internal transcribed spacer (ITS) sequences, already employed in recent studies, were obtained for 18 populations. These sequences in combination with other Saniculoideae ITS sequences available from GenBank have been used for a further phylogenetic analysis. The results agree with the current classification of Saniculoideae in placing P. gussonei in tribe Saniculeae, since P. gussonei is in basal position to Sanicula. According to intraspecific chloroplast DNA diversity, no different haplotypes were detected. In addition to molecular data, morphology, cytology, phytochemistry and conservation status have been considered in the discussion.     

Patterns of variation at a mitochondrial sequence-tagged-site locus provides new insights into the postglacial history of European Pinus sylvestris populations

Due to their maternal mode of inheritance, mitochondrial markers can be regarded as almost 'ideal' tools in evolutionary studies of conifer populations. In the present study, polymorphism was analysed at one mitochondrial intron (nad 1, exon B/C) in 23 native European Pinus sylvestris populations. In a preliminary screening for variation using a polymerase chain reaction-restriction fragment length polymorphism approach, two length variants were identified. By fully sequencing the 2.5 kb region, the observed length polymorphism was found to result from the insertion of a 31 bp sequence, with no other mutations observed within the intron. A set of primers was designed flanking the observed mutation, which identified a novel sequence-tagged-site mitochondrial marker for P. sylvestris. Analysis of 747 trees from the 23 populations using these primers revealed the occurrence of two distinct haplotypes in Europe. Within the Iberian Peninsula, the two haplotypes exhibited extensive population differentiation (PhiST = 0.59; P < or = 0.001) and a marked geographical structuring. In the populations of central and northern Europe, one haplotype largely predominated, with the second being found in only one individual of one population.     

Mitochondrial and chloroplast DNA-based phylogeny of Pelargonium (Geraniaceae)

Overall phylogenetic relationships within the genus Pelargonium (Geraniaceae) were inferred based on DNA sequences from mitochondrial(mt)-encoded nad1 b/c exons and from chloroplast(cp)-encoded trnL (UAA) 5' exon-trnF (GAA) exon regions using two species of Geranium and Sarcocaulon vanderetiae as outgroups. The group II intron between nad1 exons b and c was found to be absent from the Pelargonium, Geranium, and Sarcocaulon sequences presented here as well as from Erodium, which is the first recorded loss of this intron in angiosperms. Separate phylogenetic analyses of the mtDNA and cpDNA data sets produced largely congruent topologies, indicating linkage between mitochondrial and chloroplast genome inheritance. Simultaneous analysis of the combined data sets yielded a well-resolved topology with high clade support exhibiting a basic split into small and large chromosome species, the first group containing two lineages and the latter three. One large chromosome lineage (x = 11) comprises species from sections Myrrhidium and Chorisma and is sister to a lineage comprising P. mutans (x = 11) and species from section Jenkinsonia (x = 9). Sister to these two lineages is a lineage comprising species from sections Ciconium (x = 9) and Subsucculentia (x = 10). Cladistic evaluation of this pattern suggests that x = 11 is the ancestral basic chromosome number for the genus.     

Confirmation of a natural hybrid species in Petrocosmea (Gesneriaceae) based on molecular and morphological evidence

A natural hybrid species in Petrocosmea named Longianthera in Yanshan County,Yunnan Province is confirmed for the first time based on molecular and morphological evidence.The character count procedure of the variable characters show that Longianthera populations are characteristic of the intermediate morphological traits between its putative parents Yanshan and Petrocosmea martinii.The nuclear ribosomal internal transcribed spacer region and three chloroplast regions of matK,trnL-F,and trnT-L are sequenced in the putativehybrid and the related species.Both alignment of DNA sequences and the phylogenetic trees could exclude all the other species in Petrocosmea as the parental species except for Yanshan and P martinii.Eight haplotypes in the 31 internal transcribed spacer sequences and six haplotypes in 42 cpDNA sequences were found from 14 individuals of Longianthera populations.The analyses of DNA sequences,haplotypes,and phylogenetic trees indicate that Longianthera is likely a hybrid species between its putative parents Yanshan and P martinii,in which Yanshan might be the most possible maternal parent.Several factors may contribute to the natural hybridization between these two parental species in Petrocosmea,such as the overlapped geographic distribution,habitats,flowering periods,and shared pollinators.Finally,the new species of Yanshan and the natural hybrid species of Longianthera are described.     

Evolutionary analysis of Pinus densata (Masters), a putative Tertiary hybrid.

Summary Restriction fragment analysis and heterologous hybridization of chloroplast (cp) DNA was used to develop species-specific markers for P. tabulaeformis, P. yunnanensis and P. massoniana. Fragment patterns created by the BclI and DraI restriction enzymes and hybridization patterns to the psbC and psbD probes were distinctive among the three species. No intraspecific variation was detected with respect to any of the cpDNA markers developed in this study. The cpDNA markers obtained were subsequently used to examine the parentage of P. densata, a putative Tertiary hybrid between P. tabulaeformis and P. yunnanensis. The analysis demonstrated for the first time that P. densata populations accommodate chloroplast genomes of P. tabulaeformis and P. yunnanensis, which strongly supports earlier suggestions of the hybrid origin of this species. It appears that P. densata represents a stabilized natural hybrid that has become adapted to high mountain environments where neither of the parental species can normally grow.     

Variation in the chloroplast DNA of Swiss stone pine (Pinus cembra L.) reflects contrasting post-glacial history of populations from the Carpathians and the Alps

Aim To characterize the genetic structure and diversity of Pinus cembra L. populations native to two disjunct geographical areas, the Alps and the Carpathians, and to evaluate the rate of genetic differentiation among populations. Location The Swiss Alps and the Carpathians. Methods We screened 28 populations at three paternally inherited chloroplast simple sequence repeats (cpSSRs) for length variation in their mononucleotide repeats. Statistical analysis assessed haplotypic variation and fixation indices. Hierarchical analysis of molecular variance (AMOVA), Mantel test, spatial analysis of molecular variance (SAMOVA) and barrier analyses were applied to evaluate the geographical partitioning of genetic diversity across the species’ range. Results Haplotypic diversity was generally high throughout the natural range of P. cembra, with the mean value substantially higher in the Carpathians (H = 0.53) than in the Alps (H = 0.35). The isolated Carpathian populations showed the highest haplotype diversity among the populations originating from the High Tatras (Velka Studena Dolina) and South Carpathians (Retezat Mountains). AMOVA revealed that only 3% of the total genetic variation derived from genetic differentiation between the two mountain ranges. Differentiation among Carpathian populations was higher (F_ST = 0.19) than among Alpine populations (F_ST = 0.04). Low, but significant, correlation was found between the geographical and genetic distances among pairs of populations (r = 0.286, P < 0.001). SAMOVA results revealed no evident geographical structure of populations. barrier analysis showed the strongest differentiation in the eastern part of the species’ range, i.e. in the Carpathians. Main conclusions The populations of P. cembra within the two parts of the species’ range still share many cpDNA haplotypes, suggesting a common gene pool conserved from a previously large, continuous distribution range. Carpathian populations have maintained high haplotypic variation, even higher than Alpine populations, despite their small population sizes and spatial isolation. Based on our results, we emphasize the importance of the Carpathian populations of Swiss stone pine for conservation. These populations comprise private haplotypes and they may represent a particular legacy of the species’ evolutionary history.     

Dynamics of allozyme heterozygosity in Siberian dwarf pine Pinus pumila (Pall.) Regel populations of the Russian Far East: comparison of embryos and maternal plants

Siberian dwarf pine, or Japanese stone pine, Pinus pumila (Pall.) Regel is widespread in eastern Siberia and the Russian Far East; the species is bird-dispersed and has a unique spreading or shrub living form. A mixed mating system (predominant outcrossing with self-pollination and matings of close relatives) leads to the formation of partly inbred progenies in P. pumila, as in the majority of other conifers. The question arises as to whether inbred individuals persist in the reproductive part of a population, which can have negative genetic consequences. The ADH, FDH, FEST, GDH, GOT, IDH, LAP, MNR, MDH, PEPCA, 6-PGD, PGI, PGM, SKDH, and SOD isozyme systems were analyzed to study the dynamics of heterozygosity in four P. pumila natural populations from the Pacific region, optimal for the species. Samples were collected in northern Koryakia, southern Kamchatka (two samples), and the Kunashir Island (Kurils). Wright's fixation index was used to estimate the level of inbreeding in embryos from dormant seeds resulting from free pollination and in maternal plants. A substantial level of inbreeding (F(IS) = 0.124-0.342) was observed in the embryo samples but not in three out of the four adult samples. The inbreeding level at the reproductive age was high only in the sample from Koryakia, which was explained by a relatively young age of plants in the population frequently affected by fires. A general increase in heterozygosity, characteristic of other conifers as well, was attributed to elimination of inbred progenies and by balancing selection for heterozygotes, which is a key factor maintaining allozyme polymorphism in populations.     

Glacial refugia of limber pine (Pinus flexilis James) inferred from the population structure of mitochondrial DNA

To make inferences about the glacial refugia that harboured the limber pine, Pinus flexilis James, we examined the range-wide population structure of mitochondrial DNA (mtDNA) with eight size variants in the second intron of nad1. The data consisted of haplotypes from 704 trees collected from 40 localities. The value of FST for these populations was 0.80, which is a much larger value than has been reported for allozymes and chloroplast DNA (cpDNA) in limber pine, and it suggests that the number of seeds moving among localities per generation is approximately 0.12. Gene flow of this magnitude would allow mutation and subsequent genetic drift to have a substantial impact on the population structure of mtDNA. The majority of the mtDNA haplotypes are restricted to minor portions of the geographical range. The data are consistent with mtDNA differentiation in seven glacial refugia, followed by dispersal out of those refugia.     

Colonization routes of Pinus sylvestris inferred from distribution of mitochondrial DNA variation

Understanding the present-day distribution of molecular variation requires knowledge about the history of the species. Past colonization routes and locations of refugia of Scots pine (Pinus sylvestris) were inferred from variation in mitochondrial DNA in material collected from 37 populations located in countries within, and immediately adjacent to the continent of Europe. Two mitochondrial regions, nad1 intron (exon B/C) and nad7 intron 1, were included in the study. Differentiation in maternally inherited mitochondria was high (G _ST′ = 0.824). Two new haplotypes were found at the nad7 intron 1. The occurrence of a 5-bp indel variant was restricted to the Turkish Kalabak population and a 32 bp only found in Central, Eastern, and Northern Europe. The complete absence of the 32-bp indel from the Mediterranean peninsulas supports the view that coniferous forests existed outside these areas during the last glacial maximum, and these populations contributed to the subsequent colonization of the northern parts of Europe. P. sylvestris shares features of its glacial and postglacial history with two other northern, cold-tolerant tree species, Picea abies and Betula sp. These three species differ from many other European trees for which pollen core and molecular evidence indicate colonization from southern refugia after the last glacial period.     

Nuclear and cytoplasmic variation within and between Eurasian Larix (Pinaceae) species

The genetic variation in nuclear and cytoplasmic markers was investigated in 28 populations belonging to Eurasian Larix species (L. decidua, L. sibirica, L. gmelinii, L. olgensis, and L. kaempferi). Nuclear genetic variation was assessed at 214 AFLP loci, and both PCR-RFLP and four microsatellite loci were used to estimate variation of the chloroplast DNA. Variation of the mitochondrial genome was measured using RFLPs. Although population differentiation at both nuclear and chloroplast markers was much weaker than at mitochondrial DNA, it nonetheless corroborated the grouping observed with mitochondrial DNA. The AFLPs led to the same population grouping as mtDNA. Notably, the presence of two ancient western and eastern groups within L. sibirica was confirmed and possible postglacial routes inferred. The genetic composition of the northernmost L. sibirica population in our sample established that it is located at the confluence of the eastern and western recolonization routes. The joint use of the three markers also indicated that populations around Lake Baikal are hybrids between L. gmelinii and L. sibirica, with L. gmelinii primarily acting as the pollinator. Finally, AFLP-based estimates of nucleotide variation were an order of magnitude larger than the strikingly low estimates of nucleotide variation recently reported in Pinus sylvestris.     

Genetic diversity and biogeography of native and introduced populations of Ulva pertusa (Ulvales,Chlorophyta)

Genetic diversity of native and introduced populations of Ulva pertusa (Ulvales, Chlorophyta) was examined using genetic markers of chloroplast, mitochondria and nuclear non‐coding region sequences. In the preliminary investigations to genetically identify the species for further analyses, U. pertusa was found only from temperate coasts of the more extensive collection sites including tropical coasts suggesting that it is a temperate species and basically not distributed in tropical regions. For chloroplast and mitochondrial sequences, repeating patterns of short tandem repeat sequences and nucleotide substitutions were used to recognize the haplotypes (genetic types). A total of 48 haplotypes based on combinations of chloroplast and mitochondrial haplotypes were recognized in the 244 specimens collected in the presumptive native range (Northeast Asia) and introduced populations (North America, Australia, New Zealand, Chile and Europe). Among them, 46 haplotypes (H1–H8 and H11–H48) were recognized in Northeast Asia, whereas only 1–5 haplotypes were recognized in the other areas. Nuclear microsatellite sequences were also analyzed. The lengths of the PCR products including the nuclear microsatellite region of 234 specimens were determined, and a total of 17 genotypes were recognized. Among them, 14 genotypes were found in Northeast Asia, whereas 1–7 genotypes were recognized in the other areas. Based on the results, the hypothesis that the native range of the species is in Northeast Asia was supported, and the populations outside this range were concluded to be non‐indigenous populations.     

Phylogeography of a northeast Asian spruce, Picea jezoensis, inferred from genetic variation observed in organelle DNA markers

Range-wide genetic variation of the widespread cold-temperate spruce Picea jezoensis was studied throughout northeast Asia using maternally inherited mitochondrial DNA and paternally inherited chloroplast DNA markers. This study assessed 33 natural populations including three varieties of the species in Japan, Russia, China, and South Korea. We depicted sharp suture zones in straits around Japan in the geographical distribution pattern of mitochondrial haplotypes (GST=0.901; NST=0.934). In contrast, we detected possible extensive pollen flow without seed flow across the straits around Japan during the past population history in the distribution pattern of chloroplast haplotypes (GST=0.233; NST=0.333). The analysis of isolation by distance of the species implied that by acting as a barrier for the movement of seeds and pollen, the sharp suture zones contributed considerably to the level of genetic differentiation between populations. Constructed networks of mitochondrial haplotypes allowed inference of the phylogeographical history of the species. We deduced that the disjunction with Kamchatka populations reflects range expansion and contraction to the north of the current distribution. Within Japan, we detected phylogeographically different types of P. jezoensis between Hokkaido and Honshu islands; P. jezoensis in Honshu Island may have colonized this region from the Asian continent via the Korean peninsula and the species in Hokkaido Island is likely to have spread from the Asian continent via Sakhalin through land bridges. Japanese endemism of mitochondrial haplotypes in Hokkaido and Honshu islands might have been promoted by separation of these islands from each other and from the Asian continent by the straits during the late Quaternary.     

Multiple origins of polyploidy and the geographic structure of Heuchera grossulariifolia

Multiple origins of polyploidy from an ancestral diploid plant species were investigated using restriction site polymorphism and sequence variation in the chloroplast DNA (cpDNA) of Heuchera grossulariifolia (Saxifragaceae). Phylogenetic analysis indicated that autopolyploidy has arisen at least twice in the evolutionary history of this species and potentially up to as many as seven times. These results suggest a greater range of independent polyploid origins as compared to a previous study of H. grossulariifolia using cpDNA restriction sites that indicated a minimum of three independent origins. Moreover, most polyploid populations did not contain cpDNA haplotypes from a single origin, but rather combined haplotypes from at least two polyploid origins. Past migration among polyploid populations of independent origin or localized polyploid formation may explain the distribution of polyploid haplotypes within and among populations. The analysis also revealed a discrepancy between relatedness and geographical location. In nearly all sympatric populations of diploids and polyploids, polyploids had the same cpDNA haplotypes as diploids from a geographically remote population. This geographical discordance has several possible explanations, including small sample sizes, extinction of parental diploid haplotypes, chloroplast introgression, and homoplasy in the cpDNA sequence data. We conclude that the recurrent formation of polyploids is an important evolutionary mechanism in the diversification of H. grossulariifolia .     

Organellar Inheritance in Liverworts: An Example of Pellia borealis

Abstract Liverwort Pellia borealis is an allopolyploid species that originated after the hybridization and chromosome doubling of two cryptic species; Pellia epiphylla species N and Pellia epiphylla species S. A sequence comparison of chloroplast tRNAUCCGly, tRNAUUULys gene introns, the mitochondrial tRNAGCUSer gene intron, and the first intron of the coxIII gene in the case of three liverwort species studied revealed that the chloroplast and mitochondrial sequences are identical in P. borealis and P. epiphylla species N but different from homologous P. epiphylla species S sequences. Both mitochondria and chloroplasts of P. borealis were thus inherited from one parent—P. epiphylla species N. Studies on 14 different populations of P. borealis gave the same result. These are the first data on organellar transmission in liverworts, the earliest land plants. Moreover, we show that the intron sequences of some organellar genes, until now not used in any systematic studies, could be very good markers in studying taxonomic relationships in closely related species and reconstructing historical events.