Extensive Introgression of Mitochondrial DNA Found between two Genetically Divergent Forms of Threespine Stickleback, Gasterosteus Aculeatus, around Japan

The genetic structure and phylogenetic relationships of Gasterosteus aculeatus around Japan were investigated for 15 populations of the Japan Sea and Pacific Ocean forms previously detected by allozyme analyses. PCR-RFLP analysis of mtDNA ND5/6 gene indicated two major divergent clades: (1) Alaskan population and (2) Russian and Japanese populations. Japanese populations were clearly subdivided into G. aculeatus populations and hariyo (G. aculeatus leiurus). However, the relationships among Japanese G. aculeatus populations did not support the genetic divergence between Japan Sea and Pacific Ocean forms shown by allozyme analyses. This suggests that mtDNA genetype similarity between the two forms could have resulted from complete replacement of mtDNA from one form to the other. MtDNA introgression is possible in two direction: from Japan Sea form to Pacific Ocean form and the reverse. The haplotype composition of each population observed in the present study suggests that the second direction is more likely. The migrant number of females per generation (Nm) between populations of the two forms was remarkablely large (9.083–infinite), suggesting that gene flow is taking place between the populations at the present time or might have occurred until recent years.     

Mitochondrial DNA variation and the evolutionary history of cryptic Gammarus fossarum types

The evolutionary history of the cryptic Gammarus fossarum species complex (Crustacea, Amphipoda) in Central Europe was approached by investigating the genetic variation in populations of a natural contact zone. Nucleotide sequence variation of a 395-bp segment of the mitochondrial 16S rRNA gene was compared to that of six nuclear allozyme loci. Three major mtDNA lineages were found, the eastern clade being consistent with the former allozyme type A. The two western clades (types B and C) were not distinguished previously. Strong sequence divergence and correlation with nuclear genetic isolation in syntopic populations, however, justifies the specific status of the three G. fossarum types. The common speciation event is believed to be very old (Miocene). The within-type mtDNA variation is probably molded by the ice ages, with type B populations being most affected. Moreover, the patch-like distribution of mtDNA type B lineages in an area near the contact zone corroborates the hypothesis of a recent colonization.     

Phylogeography and the maternal origin of the tetraploid form of the Japanese spined loach, <Emphasis Type="Italic">Cobitis biwae</Emphasis>, revealed by mitochondrial DNA analysis

The Japanese spined loach Cobitis biwae includes the tetraploid form, which has 96 chromosomes, as well as the diploid form, which has 48 chromosomes. In the present study, we analyzed the mitochondrial DNA (mtDNA) to examine the genetic relationships among 82 populations of diploid–tetraploid complexes of C. biwae. Restriction fragment length polymorphism (RFLP) analysis of the ND1 region on 202 individuals revealed that C. biwae contains three genetically divergent major groups corresponding to geographical proximities (the Eastern, Western, and Kochi groups). Phylogenetic analyses (neighbor-joining, NJ and maximum-parsimony, MP) of a part of the cytochrome b gene sequence (748bp) in 31 individuals supported the three major groups recognized by RFLP, and indicated considerable genetic differentiation between the Western group and the other two groups (average, 15.2%). The genetic relationship and distribution pattern of the three major groups hypothesized two major dispersions of C. biwae during the middle Miocene: first, the ancestor of the Eastern and Kochi groups had spread from the West through wide regions of present-day Honshu and Shikoku Islands, and following that period, the ancestor of the Western group with a different mtDNA composition, probably resulting from the mtDNA introgression from C. takatsuensis, moved into western Japan and pushed the former north eastward. All tetraploid form populations were included in the Western group and treated as a monophyletic cluster with low genetic divergence. It is notable that two diploid populations geographically adjacent to the tetraploid range were genetically closely related to the tetraploid forms. This result suggests that these diploid populations were directly related to the maternal origin of the tetraploid form.     

Population genetic structure and the effect of founder events on the genetic variability of introduced sika deer, Cervus nippon, in Germany and Austria

The relationships among 214 wild-living sika deer from five locations in Germany and two in Lower Austria were examined using mitochondrial DNA (mtDNA) control region sequence. A total of 18 haplotypes are grouped consistently into two major divergent clades, A and B, which differ by a mean of 8.4% sequence divergence. Recently introduced sika deer showed a complex pattern of population structuring, which probably results from historical vicariance in at least two unknown source populations from southeastern Asia (as previously described by morphological and mtDNA findings), and subsequent population admixture as a result of human-mediated restocking. A strong genetic differentiation among populations was indicated by a global _ST value of 0.78 reflecting mainly the differential distribution of clades A and B haplotypes. There was no association between related haplotypes and their distribution among local populations. These indicate that genealogy is a better predictor of the genetic affinity among most sika deer populations than their present-day locations. The abundant mitochondrial divergence we observed, may reflect a subspecies differentiation and could be associated with phenotypic differences among the introduced sika deer.An erratum to this article can be found at     

Phylogenetic relationships of silver crusian carp Carassius auratus gibelio, C. auratus cuvieri, crucian carp Carassius carassius, and common carp Cyprinus carpio as inferred from mitochondrial DNA variation

PCR-RFLP analysis of the ND3/ND4L/ND4 and 12S/16S rRNA regions and nucleotide sequence variation of the cytochrome b gene were used to study the mtDNA divergence in species of the family Cyprinidae, to examine the phylogenetic relationships of the species, and to identify their taxonomic status. The results indicated that an ancestral form diverged into silver crucian carp and crucian carp after its separation from the common carp lineage. The divergence of continental Carassius auratus gibelio and Japanese C. auratus cuvieri occurred more recently. Two well distinguishable mtDNA phylogroups, suggesting divergent evolution, were observed in continental C. auratus gibelio populations. The divergence was possibly related to the formation of two silver crucian carp groups with different types of reproduction, triploid gynogenetic and diploid gonochoric. At the same time, the results supported the high probability of current genetic exchange between the forms. In view of these findings and high morphological similarity of the two forms, they were not considered to be separate species.     

Estimation of genetic diversity among Turkish kale populations (<Emphasis Type="Italic">Brassica oleracea</Emphasis> var. <Emphasis Type="Italic">acephala</Emphasis> L.) using RAPD markers

Twenty populations of kale (Brassica oleracea var. acephala L.) selected from 127 populations in terms of yield and leaf quality characteristics as superior types using weight-based ranking method from the Black Sea Region of Turkey were evaluated at the DNA level using randomly amplified polymorphic DNA (RAPD) markers compared to some morphological characters. The seven primers selected from 100 decamers used generated 110 bands, of which 60 (54.5%) were polymorphic. Jaccard’s genetic distances were calculated and dendrogram was generated using the UPGMA algorithm. The dendrogram obtained was classified into three main groups and four subgroups. The accessions showed a limited clustering as compared to morphological characters such as the number of leaves, intentation of the leaf margin, leaf and midrib color, and thickness of midrib, than geographical characteristics. Leaf color and midrib thickness characters clustered in the same group as OR49 and G18 accessions; S20, G6, and OR37 accessions, respectively. The text was submitted by the authors in English.     

Molecular and morphological differences between two geographic populations of Salanx ariakensis (Salangidae) from Korea and Japan

Geographic variations of a salangid, Salanx ariakensis, from Korea and Japan, based on partial mtDNA cyt b gene sequences and morphometric data, are presented and compared with Salanx cuvieri from China. Analyses of molecular variance (AMOVA) suggested that the two populations of S. ariakensis differed significantly from each other in pairwise fixation index (F _ST = 0.43), although their reciprocal monophyly was not constructed in the phylogenetic analysis. The phylogenetic analysis, however, supported the reciprocal monophyly of S. ariakensis (Korean population + Japanese population) and S. cuvieri. Differences in genetic structure between the two populations of S. ariakensis were suggested by diversity indices, mismatch distribution shape, and minimum spanning network. In particular, diversity indices indicated that the Korean population was historically larger and more stable than the Japanese population. In addition, both the principal component analysis (PCA) and canonical discriminant analysis (CDA) for morphometric characters, and the Kruskal–Wallis test for some meristic characters, showed that the two populations of S. ariakensis differed from each other, although morphological differences between the two populations of S. ariakensis were smaller than those between S. ariakensis and S. cuvieri. Such morphological differences were consistent with the differences in mtDNA.     

COLOR PATTERN EVOLUTION,ASSORTATIVE MATING,AND GENETIC DIFFERENTIATION IN BRIGHTLY COLORED BUTTERFLYFISHES (CHAETODONTIDAE)

In butterflyfishes (Chaetodontidae), color pattern evolves rapidly and is often the only morphological trait separating closely related species. Vivid coloration is frequently assumed to provide critical signals for mate recognition and mate choice, but few direct experimental tests are available. Here we analyze the relationship between color pattern change, mate choice, and genetic differentiation in a group of three very closely related allopatric butterflyfishes. We found that in only one member of this group, Chaetodon multicinctus, is color pattern evolution associated with mate preference and genetic divergence. For its two sister species, C. punctatofasciatus and C. pelewensis, color pattern change has not resulted in assortative mating (based on laboratory pairing experiments and field observations) or in significant mtDNA or allozyme differentiation. In a contact zone on reefs in the Solomon Islands and Papua New Guinea, hybridization between the two forms has nearly homogenized color pattern differences. Outside these areas, however, color pattern remains distinct. Genetic variation is homogeneous over a much larger geographic scale. Sequence variation in the tRNA-proline end of the mitochondrial control region and allozyme variation was distributed widely within C. punctatofasciatus and C. pelewensis, which suggests few constraints to mitochondrial or nuclear gene flow across the color pattern boundary. These contrasting patterns strongly suggest that selection is maintaining color pattern differences in allopatry in the face of potentially homogenizing levels of gene flow. The mating pattern data show that this selection is not operating on mate recognition in the strictest sense, but probably on some other aspect of the social system of these territorial fish. In this case, divergence in mating preference can follow color pattern evolution, but is not contemporaneous with it.     

Origin and differentiation of human mitochondrial DNA.

A recent study of mitochondrial DNA (mtDNA) polymorphism has generated much debate about modern human origins by proposing the existence of an "African Eve" living 200,000 years ago somewhere in Africa. In an attempt to synthesize information concerning human mtDNA genetic polymorphism, all available data on mtDNA RFLP have been gathered. A phylogeny of the mtDNA types found in 10 populations reveals that all types could have issued from a single common ancestral type. The distribution of shared types between continental groups indicates that caucasoid populations could be the closest to an ancestral population from which all other continental groups would have diverged. A partial phylogeny of the types found in five other populations also demonstrates that the myth of an African Eden was based on an incorrect "genealogical tree" of mtDNA types. Two measures of molecular diversity have been computed on all samples on the basis of mtDNA type frequencies, on one hand, and on the basis of the number of polymorphic sites in the samples, on the other. A large discrepancy is found between the two measures except in African populations; this suggests the existence of some differential selective mechanisms. The lapse of time necessary for creating the observed molecular diversity from an ancestral monomorphic population has been calculated and is found generally greater in Oriental and caucasoid populations. Implications concerning human mtDNA evolution are discussed.     

Intraspecific Genetic Admixture and the Morphological Diversification of an Estuarine Fish Population Complex

The North-east American Rainbow smelt (Osmerus mordax) is composed of two glacial races first identified through the spatial distribution of two distinct mtDNA lineages. Contemporary breeding populations of smelt in the St. Lawrence estuary comprise contrasting mixtures of both lineages, suggesting that the two races came into secondary contact in this estuary. The overall objective of this study was to assess the role of intraspecific genetic admixture in the morphological diversification of the estuarine rainbow smelt population complex. The morphology of mixed-ancestry populations varied as a function of the relative contribution of the two races to estuarine populations, supporting the hypothesis of genetic admixture. Populations comprising both ancestral mtDNA races did not exhibit intermediate morphologies relative to pure populations but rather exhibited many traits that exceeded the parental trait values, consistent with the hypothesis of transgressive segregation. Evidence for genetic admixture at the level of the nuclear gene pool, however, provided only partial support for this hypothesis. Variation at nuclear AFLP markers revealed clear evidence of the two corresponding mtDNA glacial races. The admixture of the two races at the nuclear level is only pronounced in mixed-ancestry populations dominated by one of the mtDNA lineages, the same populations showing the greatest degree of morphological diversification and population structure. In contrast, mixed-ancestry populations dominated by the alternate mtDNA lineage showed little evidence of introgression of the nuclear genome, little morphological diversification and little contemporary population genetic structure. These results only partially support the hypothesis of transgressive segregation and may be the result of the differential effects of natural selection acting on admixed genomes from different sources.     

Historic speciation and recent colonization of Eurasian monkey gobies (Neogobius fluviatilis and N. pallasi) revealed by DNA sequences,microsatellites, and morphology

Aim Hidden diversity within an invasive ‘species’ can mask both invasion pathways and confound management goals. We assessed taxonomic status and population structure of the monkey goby Neogobius fluviatilis across Eurasia, comparing genetic variation across its native and invasive ranges. Location Native populations were analysed within the Black and Caspian Sea basins, including major river drainages (Dnieper, Dniester, Danube, Don and Volga rivers), along with introduced locations within the upper Danube and Vistula river systems. Methods DNA sequences and 10 nuclear microsatellite loci were analysed to test genetic diversity and divergence patterns of native and introduced populations; phylogenetic analysis of mtDNA cytochrome b and nuclear RAG‐1 sequences assessed taxonomic status of Black and Caspian Sea lineages. Multivariate analysis of morphology was used to corroborate phylogenetic patterns. Population genetic structure within each basin was evaluated with mtDNA and microsatellite data using F_ST analogues and Bayesian assignment tests. Results Phylogenetic analysis of mitochondrial and nuclear sequences discerned a pronounced genetic break between monkey gobies in the Black and Caspian Seas, indicating a long‐term species‐level separation dating to c. 3 million years. This pronounced separation further was confirmed from morphological and population genetic divergence. Bayesian inference showed congruent patterns of population structure within the Black Sea basin. Introduced populations in the Danube and Vistula River basins traced to north‐west Black Sea origins, a genetic expansion pattern matching that of other introduced Ponto‐Caspian gobiids. Main conclusions Both genetic and morphological data strongly supported two species of monkey gobies that were formerly identified as subspecies: N. fluviatilis in the Black Sea basin, Don and Volga Rivers, and the Kumo‐Manych Depression, and Neogobius pallasi in the Caspian Sea and Volga River delta. Genetic origins of introduced N. fluviatilis populations indicated a common invasion pathway shared with other introduced Ponto‐Caspian fishes and invertebrates.     

Analysis of mitochondrial DNA in Bolivian llama,alpaca and vicuna populations: a contribution to the phylogeny of the South American camelids

The objectives of this work were to assess the mtDNA diversity of Bolivian South American camelid (SAC) populations and to shed light on the evolutionary relationships between the Bolivian camelids and other populations of SACs. We have analysed two different mtDNA regions: the complete coding region of the MT‐CYB gene and 513 bp of the D‐loop region. The populations sampled included Bolivian llamas, alpacas and vicunas, and Chilean guanacos. High levels of genetic diversity were observed in the studied populations. In general, MT‐CYB was more variable than D‐loop. On a species level, the vicunas showed the lowest genetic variability, followed by the guanacos, alpacas and llamas. Phylogenetic analyses performed by including additional available mtDNA sequences from the studied species confirmed the existence of the two monophyletic clades previously described by other authors for guanacos (G) and vicunas (V). Significant levels of mtDNA hybridization were found in the domestic species. Our sequence analyses revealed significant sequence divergence within clade G, and some of the Bolivian llamas grouped with the majority of the southern guanacos. This finding supports the existence of more than the one llama domestication centre in South America previously suggested on the basis of archaeozoological evidence. Additionally, analysis of D‐loop sequences revealed two new matrilineal lineages that are distinct from the previously reported G and V clades. The results presented here represent the first report on the population structure and genetic variability of Bolivian camelids and may help to elucidate the complex and dynamic domestication process of SAC populations.     

Morphological stasis in the Eurytemora affinis species complex (Copepoda: Temoridae)

Morphological stasis has long been regarded as one of the most challenging problems in evolutionary biology. This study focused on the copepod species complex, Eurytemora affinis, as a model system to determine pattern and degree of morphological stasis. This study revealed discordant rates of morphological differentiation, molecular evolution, and reproductive isolation, where speciation was accompanied by lack of morphological differentiation in secondary sex characters. Comparisons were made among phylogenies based on morphometrics, nuclear (allozyme) loci, and mitochondrial DNA (mtDNA) sequences from cytochrome oxidase I, for a total of 43 populations within the complex. These systematic relationships were also compared to patterns of reproductive isolation. In addition, genetic subdivision of nuclear molecular (allozyme) markers (G _ST) and quantitative (morphological) characters (Q _ST) were determined to infer evolutionary forces driving morphological differentiation. The morphometric phylogeny revealed that all clades, excluding the European clade, were morphologically undifferentiated and formed a polytomy (multifurcation). Morphometric distances were not correlated with mtDNA distances, or with patterns of reproductive isolation. In contrast, nuclear and mtDNA phylogenies were mostly congruent. Reproductive isolation proved to be the most sensitive indicator of speciation, given that two genetically and morphologically proximate populations showed evidence of hybrid breakdown. Quantitative genetic (morphological) subdivision (Q _ST = 0.162) was lower than nuclear genetic subdivision (G _ST = 0.617) for four laboratory-reared North American populations, indicating retarded evolution of morphological characters. This result contrasts with most other species, where Q _ST typically exceeds G _ST as a result of directional selection. Thus, in all but the European populations, evolution of the secondary sex characters was marked by morphological stasis, even between reproductively-isolated populations.     

Molecular and morphological analysis of endangered species <Emphasis Type="Italic">Gymnodiptychus integrigymnatus</Emphasis> (Teleostei: Cyprinidae)

Gymnodiptychus integrigymnatus is a critically endangered species endemic to the Gaoligongshan Mountains. It was thought to be only distributed in several headwater-streams of the Longchuanjiang River (west slope of the Gaoligongshan Mountains, belonging to the Irrawaddy River drainage). In recent years, dozens of G. integrigymnatus specimens have been collected in some streams on the east slope of the Gaoligongshan Mountains (the Salween drainage). We performed a morphological and genetic analyses (based on cytochrome b and D-loop) of the newly discovered populations of G. integrigymnatus to determine whether the degree of separation of these populations warrants species status. Our analysis from the cytochrome b gene revealed that nine individuals from the Irrawaddy drainage area and seven individuals from the Salween drainage area each have only one unique haplotype. The genetic distance between the two haplotypes is 1.97%. Our phylogenetic analysis revealed that G. integrigymnatus is closely related to highly specialized schizothoracine fishes. Analysis from the mitochondrial control region revealed that G. integrigymnatus has relatively high genetic diversity (π was 0.00891 and h was 0.8714), and individuals from different river drainages do not share the same haplotypes. The AMOVA results indicated 87.27% genetic variability between the Salween and Irrawaddy populations. Phylogenetic trees show two major geographic groups corresponding to the river systems. We recommend that G. integrigymnatus should be considered as a high priority for protected species status in the Gaoligongshan Mountains National Nature Reserve, and that the area of the Gaoligongshan Mountains National Nature Reserve should be expanded to cover the entire distribution of G. integrigymnatus. Populations of G. integrigymnatus from different river systems should be treated as evolutionarily significant units.     

Morphological and Molecular-Genetic Polymorphism of <Emphasis Type="Italic">Canthocamptus staphylinus</Emphasis> Jurine (Harpacticoida,Copepoda, Crustacea)

External morphological and genetic structures of 94 individuals of Canthocamptus staphylinus Jurine (Harpacticoida, Copepoda, Crustacea) from ten European water bodies differing in type, including species type locality, have been analyzed. Significant distinctions of populations on six morphological features and morphometric indexes are established. The variability of both morphological and genetic markers is noted. As a result, two main species morph forms are allocated, typical and small. According to nucleotide, the variety of mitochondrial DNA harpacticoid specimens falls into ten haplotypes and three clades on the phylogenetic tree. One of them corresponds with the group isolated on morphological features (harpacticoids from the Sysola River basin, Komi Republic). The same-sex population from Lake Pääjärvi (Finland), which is morphologically indistinguishable from the population from a type locality, is considerably divergent by nucleotide sequences of mtDNA. The role of geographical isolation and ecological factors in C. staphylinus microevolution is shown.     

Phylogeography of lateral plate dimorphism in the freshwater type of ninespine sticklebacks, genus Pungitius

The freshwater type of ninespine sticklebacks, genus Pungitius, is widely distributed in northern Japan and reproductively isolated from other genetically divergent types endemic to small regions in Japan. This type expresses dimorphism in its lateral plate morphology: complete and partial row morphs. The two morphs show a parapatric distribution in Japan. To clarify the process involving the distribution of these two morphs, we examined their phylogeography based on restriction fragment length polymorphism of an entire mitochondrial DNA (mtDNA). The survey was carried out with seven restriction enzymes on the populations of the freshwater type collected from 41 localities across the distribution range in Japan, and 6 further Pungitius populations from the Okhotsk Sea coast of Russia were appended. An unweighted pair-group method with arithmetic averages (UPGMA) tree among 54 mtDNA haplotypes resolved eight clustering groups that differed in sequence divergence by approximately 1.3%–2.1%. Two of the eight groups were found only in Russia. mtDNA phylogenies constructed by neighbor-joining and Wagner parsimony methods suggested that the haplotypes of each plate morph were polyphyletic. The geographic distribution pattern of these groups suggests that they should be classified into two broad categories, one with extensive distribution and the other with localized distribution of the constituent haplotypes within a group. The former groups were found mainly in the populations with the completely plated morph and the latter groups with the partially plated morph. It is supposed that twice dispersals of dimorphic or complete plated ancestors and genetic differentiation during the interglacial played an important role in the formation of the present distribution of the two morphs in Japan. Received: March 28, 2000 / Revised: November 3, 2000 / Accepted: January 16, 2001     

Species identification of Chilean Artemia populations based on mitochondrial DNA RFLP analysis

Aim Two species of the brine shrimp, namely Artemia franciscana Kellogg and A. persimilis Piccinelli and Prosdocimi, inhabit Chile. Most studies so far have shown that A. franciscana is the most widely distributed species in Chile, with A. persimilis present only in Chilean Patagonia. In general, there is good agreement between morphological and genetic comparisons of Chilean populations with respect to species discrimination. However, a number of results indicate an overlap with some populations tending to diverge from A. franciscana and/or resembling A. persimilis. Prior to the mid 90's the use of DNA markers in Artemia was rather limited, despite their successful application in numerous other species. In this study, we investigate whether the conclusions drawn from traditional comparative tools are congruent with the pattern of genetic divergence depicted by DNA analysis at the mitochondrial level. Location Eight sites in Chile and two reference samples of A. franciscana and A. persimilis from San Francisco Bay (USA) and Buenos Aires (Argentina), respectively. Methods Restriction fragment length polymorphism (RFLP) analysis of a 535 bp segment of the mitochondrial 16S rRNA gene with nine restriction enzymes in 240 individuals. Results No haplotype was shared between the two species. Five restriction enzymes produced species‐specific patterns, enabling the unambiguous assignment of populations to species. Very high (100%) bootstrap values supported the clustering of haplotypes in two groups corresponding to the two species. The two species were clearly differentiated with average sequence divergence of 12.3%. High genetic differentiation was also found among con‐specific populations of A. franciscana with an F_ST estimate of 91%. Main conclusions The mitochondrial DNA (mtDNA) results of this study show a broadly similar pattern to those of previous allozyme and nuclear DNA analyses, with the two New World species appearing as highly divergent. The presence of A. persimilis in southern Chile (Chilean Patagonia) was confirmed. Hence, a species previously regarded as geographically restricted mainly to Argentina, appears to have expanded its range. Populations of A. franciscana appear highly structured with a level of inter‐population genetic differentiation much higher for mtDNA than previously reported with allozymes. Clustering of these populations does not follow a clear geographic pattern. The identification of population‐specific genetic markers for A. persimilis and A. franciscana will help to tackle further aspects of the speciation patterns of these species.     

Plastid DNA diversity in natural populations of Beta maritima showing additional variation in sexual phenotype and mitochondrial DNA

Summary Plants of two natural populations of Beta maritima, characterized by high percentages of male-sterile plants, have been investigated for organelle DNA polymorphism. We confirm the two classes of mitochondrial DNA variation previously described: (i) mitochondrial DNA (mtDNA) type N is associated with male fertility, whereas mtDNA type S can cause cytoplasmic male sterility (CMS); (ii) the 10.4-kb linear plasmid is observed in both types of mitochondria and is not correlated with the cytoplasmic male sterility occurring in this plant material. A third polymorphism is now described for chloroplast DNA (ctDNA). This polymorphism occurs within single populations of Beta maritima. Three different ctDNA types have been identified by HindIII restriction analysis. Among the plants studied, ctDNA type 1 is associated with N mitochondria and type 2 with S mitochondria. Chloroplast DNA type 3 has been found both in a fertile N plant and in a sterile S plant. This finding suggests that the chloroplast DNA polymorphism reported is not involved in the expression of male sterility. A comparison with Beta vulgaris indicates that ctDNA type 3 of Beta maritima corresponds to the ctDNA of fertile sugar beet maintainer lines. The three types of Beta maritima ctDNA described in this study differ from the ctDNA of male-sterile sugar beet.