A catalogue of the nominal species of the monogenean family Dactylogyridae Bychowsky, 1933 (excluding Dactylogyrus Diesing, 1850)

A list of the nominal species of the Dactylogyridae Bychowsky, 1933 (with the exception of Dactylogyrus Diesing, 1850) is presented. It consists of almost 100 specific names in 10 genera, with their hosts (to the generic level) and geographical region. A reference list to the authorities for the taxa is included.     

One known and an unknown species of the genus Thaparocleidus Jain, 1952, infecting Sperata aor (Hamilton, 1822): comparison with species from China,on molecular basis

Sperata aor commonly called as long- whiskered cat fish or “Bada Tengan” in local fish markets harboured one new and one previously known species of genus Thaparocleidus Jain, 1952, along with two species of Cornudiscoides Kulkarni, 1969, infesting gills. Thaparocleidus aori (Rizvi, 1971) Lim, 1996, was earlier described by Rizvi therefore was briefly recorded in the present study, except the egg. The newly found species Thaparocleidus susanae n.sp was characterized by the structure of its peculiar copulatory organ. Phylogenetic relationship of the two species under study, along with 14, reterived from GenBank was established using the sequences of 28S rDNA region (Dactylogyrus Diesing, 1850 taken as an out group).     

<Emphasis Type="Italic">Monticellia santafesina</Emphasis> n. sp. (Cestoda: Proteocephalidea), a parasite of <Emphasis Type="Italic">Megalonema platanum</Emphasis> (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin,Argentina

The proteocephalidean tapeworm Monticellia santafesina n. sp. is described from the siluriform catfish Megalonema platanum (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin, Argentina. The new species is allocated to Monticellia La Rue, 1911 (Proteocephalidae: Monticelliinae) because of the cortical position of the testes, ovary, vitelline follicles and uterus, a globular scolex without a metascolex and uniloculate suckers. The new species differs from all other species of Monticellia (except for M. lenha Woodland, 1933) in possessing a vaginal canal opening anterior or posterior to the cirrus-sac. M. santafesina can be distinguished from M. lenha by the following characteristics: a larger body size; a weakly developed internal longitudinal musculature arranged in 15–35 slim bundles of muscle fibres; vitelline follicles not interrupted at the level of the cirrus-sac and vaginal canal, and with a few paramuscular and/or medullary follicles; the absence of large spinitriches on the anterior margin of the suckers; and the utilisation of Megalonema platanum (in the Paraná River basin) as its host, rather than Sorubimichthys planiceps (Spix & Agassiz) (in the River Amazon). Monticellia santafesina exhibits low values of prevalence (9%) and intensity of infection (1). Megalonema platanum was parasitised by two proteocephalidean cestodes, Rudolphiella cf. lobosa (Riggenbach, 1895) and the new species described in this paper.     

Chimaerarhynchus n. g. andPatellobothrium n. g., two new genera of trypanorhynch cestodes with unique poeciloacanthous armatures,and a reorganisation of the poeciloacanthous trypanorhynch families

Chimaerarhynchus rougetae n. g., n. sp. is described fromSqualus acanthias andCentrophorus sp. from the coast of Senegal, and differs from all other trypanorhynch genera in having a chainette composed of dissimilar elements, that is, double-winged hooks alternating with pairs of hooks each with a single lateral wing. The new genus is allocated to the Gymnorhynchidae Dollfus, 1935.Patellobothrium quinquecatenatum n.g., n. sp. is described from the spiral intestine ofSphyrna mokarran from Darwin, Northern Territory, Australia and plerocerci fromRachycentron canadus from Queensland, Australia. The genus is distinguished from all others in possessing five chainettes. It is allocated to the family Mustelicolidae Dollfus, 1969. The relationships of all genera of trypanorhynchs possessing chainettes are discussed, and they are divided into three groups: (1) Dasyrhynchidae Dollfus, 1935, Lacistorhynchidae Guiart, 1927, Mustelicolidae and Hornelliellidae Yamaguti, 1954 are considered closely related since all genera possess two bothridia, a hermaphroditic duct and have hollow hooks; (2) Gymnorhynchidae, amended to contain onlyGymnorhynchus Rudolphi, 1819 andChimaerarhynchus n.g., is distinct in possessing four bothridia, an accessory seminal vesicle and hollow hooks; (3) Mixodigmatidae Dailey & Vogelbein, 1982, amended to includeMixodigma Dailey & Vogelbein, 1982 andHalysiorhynchus Pintner, 1913 has four bothridia, lacks seminal vesicles and a hermaphroditic duct and has solid hooks.A new family Molicolidae n. fam. is erected forMolicola Dollfus, 1935 andStragulorhynchus Beveridge & Campbell, 1988. The new family has a poeciloacanthous armature, and is distinguished by possessing a band of hooks on the external surface of the tentacle, four sessile bothridia and an acessory seminal vesicle.Myrmillorhynchus Bilqees, 1980 is suppressed as a synonym ofPterobothrium Diesing, 1850.Neogymnorhynchus Bilquees & Shah, 1982, is suppressed as a synonym ofPterobothrium, with the type species,N. platycephali becoming a synonym ofP. heteracanthum Diesing, 1850.Eulacistorhynchus Subhapradha, 1957 is considered agenus inquirendum;Gymnorhynchus cymbiumi Chincholikar & Shinde, 1977 is also a synonym ofPterobothrium heteracanthum Diesing, 1850.     

A new genus of Bucephalidae Poche, 1907 (Trematoda: Digenea) for three new species infecting the yellowtail pike,Sphyraena obtusata Cuvier (Sphyraenidae), from Moreton Bay,Queensland, Australia

Three new species of the family Bucephalidae Poche, 1907 (Trematoda: Digenea) are described from the yellowtail pike, Sphyraena obtusata Cuvier (Sphyraenidae), from Moreton Bay, Queensland, Australia. The three species are morphologically consistent with the present broad concept of the genus Bucephalus Baer, 1827, but significant phylogenetic and ecological differences relative to the type-species of Bucephalus require the proposal of a new genus. Aenigmatrema n. g. is proposed for A. undecimtentaculatum n. sp. (type-species), A. inopinatum n. sp. and A. grandiovum n. sp. In addition, based on morphological, ecological and biogeographical similarities, we recombine two existing species of Bucephalus as Aenigmatrema kaku (Yamaguti, 1970) n. comb. and Aenigmatrema sphyraenae (Yamaguti, 1952) n. comb. Although the three species described in this study are extremely morphologically similar, they can be differentiated from each other, and from A. kaku and A. sphyraenae, morphometrically on the basis of egg size, tentacle number and a combination of the caecum and vitelline field lengths. Complete ITS2 rDNA, partial 28S rDNA and partial cox1 mtDNA sequence data were generated for the three new species, which formed a well-supported clade in all 28S phylogenetic analyses. An expanded phylogenetic tree for the subfamily Bucephalinae Poche, 1907 is presented, demonstrating unresolved issues with the morphology-based taxonomy of the subfamily. The three largest genera, Bucephalus, Rhipidocotyle Diesing, 1858 and Prosorhynchoides Dollfus, 1929 remain extensively polyphyletic, indicating the need for significant further systematic revision.

     

Ithyoclinostomum yamagutii n. sp. (Digenea: Clinostomidae) in the great blue heron Ardea herodias L. (Aves: Ardeidae) from Mississippi,USA

With only six recognised genera, the family Clinostomidae Lühe, 1901 remains a global research interest of parasitologists and ecologists. Recent efforts have focused on providing molecular data to investigate species diversity, elucidate life-cycles, and make inferences on the group’s evolutionary history. Of the clinostomid genera, the monotypic Ithyoclinostomum Witenberg, 1926 has remained more enigmatic compared to the commonly encountered Clinostomum Leidy, 1856. Recent morphological and molecular evidence from metacercariae suggests a second Ithyoclinostomum species may exist in freshwater cichlids in Central America and Mexico. In a recent survey of great blue herons Ardea herodias L. from commercial catfish production farms in Mississippi, USA, two specimens of an abnormally large (> 20 mm) clinostomid were encountered in the oesophagus of a single bird. These specimens were identified as an Ithyoclinostomum sp. morphologically distinct from the only nominal species Ithyoclinostomum dimorphum (Diesing, 1850). Using morphological and molecular data these adult specimens were confirmed as conspecific with the larval metacercariae previously described from Central America and Mexico and represent the novel species, Ithyoclinostomum yamagutii n. sp.

     

Identification of Monogenea made easier: a new statistical procedure for an automatic selection of diagnostic linear measurements in closely related species

We introduce a new statistical method to select which morphological characters are most useful to identify monogenean species. The method estimates the average size overlap of candidate diagnostic structures among a set of species to individuate those that mostly differ between the species. To demonstrate our approach, we report a comprehensive analysis conducted on two of the most species‐rich monogenean genera: Dactylogyrus Diesing, 1850 and Gyrodactylus von Nordmann, 1832. We demonstrate that, in contrast to common taxonomic practice, very few but highly diagnostic measurements are necessary to correctly identify a specimen. In particular, we found that most of Dactylogyrus and Gyrodactylus species can be classified on the basis of the width of the supplementary connecting bar and of the length of the hook sickle, respectively.     

CRYPTOMONAD EVOLUTION: NUCLEAR 18S rDNA PHYLOGENY VERSUS CELL MORPHOLOGY AND PIGMENTATION1

A nuclear18S rDNA phylogeny for cryptomonad algae is presented, including 11 species yet to be investigated by molecular means. The phylogenetic positions of the cryptomonad genera Campylomonas and Plagioselmis are assessed for the first time. Campylomonas groups most closely with morphologically similar species with the same accessory pigment from the genus Cryptomonas. Plagioselmis groups with the genera Teleaulax and Geminigera forming a clade whose members are united by unusual thylakoid arrangement. Nuclear 18S rDNA phylogeny divides cryptomonads into seven major lineages, two of which consist of the monospecific genera Proteomonas and Falcomonas. Analysis of nuclear18S rDNA sequence supports suggestions that a Falcomonas‐like cryptomonad gave rise to all other blue‐green cryptomonads. New sequence from the plastid‐lacking cryptomonad genus Goniomonas is also included, and the order of divergence of the major cryptomonad lineages is discussed. The morphology, number, and pigmentation of the cryptomonad plastidial complex are congruent with nuclear 18S rDNA phylogenies. Host cell features, such as periplast type, furrow/gullet system, and cell shape, can be more variable and may be markedly different in species that are closely related by nuclear 18S rDNA phylogeny. Conversely, some species that are not closely related by molecular phylogeny may display a very similar, possibly primitive, periplast and furrow morphology.     

New taxa refresh the phylogeny and classification of pleurostomatid ciliates (Ciliophora,Litostomatea)

A high diversity of pleurostomatid ciliates has been discovered in the last decade, and their systematics needs to be improved in the light of new findings concerning their morphology and molecular phylogeny. In this work, a new genus, Protolitonotus gen. n., and two new species, Protolitonotus magnus sp. n. and Protolitonotus longus sp. n., were studied. Furthermore, 19 novel nucleotide sequences of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2 were collected to determine the phylogenetic relationships and systematic positions of the pleurostomatid ciliates in this study. Based on both molecular and morphological data, the results demonstrated that: (i) as disclosed by the sequence analysis of SSU rDNA, LSU rDNA and ITS1‐5.8S‐ITS2, Protolitonotus gen. n. is sister to all other pleurostomatids and thus represents an independent lineage and a separate family, Protolitonotidae fam. n., which is defined by the presence of a semi‐suture formed by the right somatic kineties near the dorsal margin of the body; (ii) the families Litonotidae and Kentrophyllidae are both monophyletic based on both SSU rDNA and LSU rDNA sequences, whereas Amphileptidae are non‐monophyletic in trees inferred from SSU rDNA sequences; and (iii) the genera Loxophyllum and Kentrophyllum are both monophyletic, whereas Litonotus is non‐monophyletic based on SSU rDNA analyses. ITS1‐5.8S‐ITS2 sequence data were used for the phylogenetic analyses of pleurostomatids for the first time; however, species relationships were less well resolved than in the SSU rDNA and LSU rDNA trees. In addition, a major revision to the classification of the order Pleurostomatida is suggested and a key to its families and genera is provided.     

Nuclear DNA content,base composition,heterochromatin and rDNA in Picea omorika and Picea abies

Two closely related spruces, Picea abies and Picea omorika, a Balkan paleoendemic species, often share habitats, yet never hybridize in nature. The present study adresses their characteristics such as nuclear DNA content, base composition, heterochromatin and rDNA pattern. The genome size of P. abies was 10% larger than that of P. omorika when assessed by flow cytometry, respectively 2C=37.2 pg and 33.8 pg; although when estimated as total chromosome length it was virtually the same. The heterochromatin Chromomycin-A (CMA)/ DAPI fluorochrome banding patterns of both P. abies and P. omorika are given here for the first time. Simultaneous FISH (fluorescent in situ hybridization) using 18S-26S and 5S rDNA probes revealed 16 18S rDNA sites in P. omorika, 12 18S rDNA sites in P. abies, and a single 5S rDNA locus in both species. The genomes have about 41% GC. The number and position of CMA/DAPI bands and rDNA loci provide good chromosome markers to clarify the karyotypes of the two species. Received: 18 October 2000 / 14 June 2001     

Phylogenetic Analysis of the Genus Bifidobacterium and Related Genera Based on 16S rDNA Sequences

The 16S rRNA gene sequences were determined for type strains of 21 Bifidobacterium species. A phylogenetic tree was constructed using the determined sequences and sequences from DNA databases, which contain the sequences of 11 type strains of Bifidobacterium species and 11 strains of related genera. All species of the genus Bifidobacterium and Gardnerella vaginalis ATCC 14018 belonged to a cluster phylogenetically distinct from the other genera. The cluster was divided into two subclusters: subcluster 1 composed of most species of Bifidobacterium and G. vaginalis, and subcluster 2 consisting of two species, B. denticolens and B. inopinatum; both of which were isolated from human dental caries. In the genus Bifidobacterium, four groups of species are known to be moderately to highly related by DNA-DNA hybridization. The four groups of species exhibited more than 99% similarity among their 16S rDNA sequences within each group. These results indicated that species with around 99% or more similarity in their 16S rDNA sequences should be confirmed for species identities.     

Phylogenetic relationships within Nephtyidae (Polychaeta,Annelida)

Ravara, A., Wiklund, H., Cunha, M. R. & Pleijel, F. (2010). Phylogenetic relationships within Nephtyidae (Polychaeta, Annelida). —Zoologica Scripta, 39, 394–405. We present the first phylogeny of nephtyids, a common, soft‐bottom living polychaete family comprising five genera and over 100 species. Characters used to distinguish nephtyid genera are a matter of controversy and considerable confusion remains as to the generic delineations. The phylogeny is estimated with molecular data from the mitochondrial genes cytochrome oxidase I and 16S rDNA, the nuclear genes 18S rDNA and 28S rDNA and morphological data. The results reveal two well‐supported major clades, corresponding in part to the two main genera of the family, Aglaophamus and Nephtys. The species Nephtys pulchra and Nephtys australiensis are transferred to Aglaophamus, and new diagnoses for the genera are provided. Dentinephtys is synonymized with Nephtys, and Nephtys cornuta is sister to the remaining nephtyids and is referred to the new genus Bipalponephtys, together with Nephtys danida and Micronephthys neotena. Micronephthys is sister to Nephtys and Inermonephtys is of uncertain position.     

贵州寒武系杷榔组Sphenothallus Hall,1847的发现及古生态意义*

在安徽省萧县凤凰山剖面炒米店组中上部(江山阶上部到第十阶)岩层中采得丰富的索克虫科三叶虫标本。共计4属6种(含2新种), 包括Eosaukia bella (Walcott, 1906)、E. anhuiensis sp. nov.、Lophosaukia orientalis (Kobayashi, 1933)、Prosaukia campe (Walcott, 1905)和P. xiaoxianensis sp. nov.、Lichengia onigawara Kobayashi, 1942。在对属征进行修订与讨论的基础上, 通过对比这些属的模式种及其他种, 对4个旧种进行了再研究和种征厘定, 最后对这6个种的谱系关系展开了简要讨论。     

皖北地区寒武系芙蓉统炒米店组中上部的索克虫类三叶虫*

塔里木盆地塔中台地奥陶系海百合茎化石丰富。本文通过研究塔中35井上奥陶统良里塔格组和桑塔木组岩芯中的海百合与其共生生物的关系, 讨论了海百合化石的古生态。在塔中35井上奥陶统取芯中识别出7种海百合茎类型: 圆圆茎、星星茎、星圆茎、椭圆圆茎、星椭圆茎、圆角星星茎和不规则星茎, 根据茎板形态划分为五射茎板组(Pentameri)、椭圆茎板组(Elliptici)、圆茎板组(Cyclici)、特殊茎板组(Varii)四种组合类型; 统计了海百合茎化石各种切面的大小和百分含量; 结合岩性分析了每段地层的沉积环境。研究发现, 在局限泻湖环境下, 蓝细菌–四分珊瑚为主的生物组合中不见海百合化石碎片; 仅见腹足类和介壳类化石的细砂屑滩中, 偶见细小的海百合茎化石; 在开阔海环境中, 海百合广泛与苔藓虫、管孔藻、粗枝藻等共生。在海百合–苔藓虫组合中, 海百合茎板的类型最丰富多样, 五射茎板组、椭圆茎板组、圆茎板组、特殊茎板组等四种茎板组合类型都存在; 在管孔藻–海百合组合中, 海百合茎板主要为圆茎板类型, 粗大、密集, 海百合茎碎片含量最高; 在海百合–粗枝藻组合中, 海百合茎板的数量减少、大小变小, 但茎板的类型比较丰富, 四种茎板组合类型都有。由此认为, 塔中台地上奥陶统沉积期, 海百合生长的首选环境为开阔台地, 并受水动力能量和水体清洁度控制: 水动力能量高, 水体清洁, 海百合繁盛; 水动力能量低, 水体动荡浑浊, 海百合可以生存; 水动力能量低、较为动荡、微生物席发育的环境, 不利于海百合生存。     

Chromosomal mapping of the major and minor ribosomal genes, (GATA)<Subscript>n</Subscript> and U2 snRNA gene by double-colour FISH in species of the Batrachoididae family

In the present study dual-colour fluorescence in situ hybridization (FISH) was performed to study the chromosomal distribution of 18S and 5S rDNAs, (GATA)_n and 5S rDNA, and U2 snRNA and 18S rDNA in four species of Batrachoididae family: Amphichthys cryptocentrus, Batrachoides manglae, Porichthys plectrodon and Thalassophryne maculosa. The 18S rDNA signals were present in only one pair of chromosomes in all the four Batrachoididae species. The 5S rDNA was mapped on one pair of chromosomes, except in B. manglae, which showed a hybridization signal in two pairs. The two ribosomal genes are located on different chromosome pairs, except in A. cryptocentrus, in which they appear co-located. In all the cases, the (GATA)_n probe produced disperse hybridization signals in all four species. The U2 snRNA signals appear very widely scattered in A. cryptocentrus, P. plectrodon, but show a degree of clustering in a specific chromosome pair in B. manglae. In T. maculosa, they are thinly dispersed and strong hybridization signals are observed co-located to the 18S rDNA-bearing chromosomes. Finally, a double-colour FISH with U2 snRNA and 5S rDNA probes was performed in B. manglae, and this showed that these genes were not co-located. These results have been compared with those from another Batrachoididae species, and evolutive processes of these species are discussed.     

The first report of two species of <Emphasis Type="Italic">Polyporus</Emphasis> (Polyporaceae,Basidiomycota) from South Korea

Based on morphological examination, two species of Polyporus, P. dictyopus, and P. tuberaster, were identified, which constitutes the first record of these species in South Korea. To confirm their affinity within the genus Polyporus, the phylogenetic relationships of Polyporus and allied genera were established from nuclear large subunit ribosomal DNA (nLSU rDNA) sequences, and a morphological diagnostic key is presented to clarify the Korean species of Polyporus.     

Evolution of rDNA FISH patterns in the Fagaceae

The Fagaceae is one of the most important plant families in European forest ecosystems, and it includes several genera distributed in the Northern hemisphere. In this work we studied the genome organization and evolution within the family, by karyotyping and physically mapping rDNA in ten European and Asian species of the genera Fagus, Quercus, and Castanea. All of the species studied had a chromosome number of 2n=2x=24, except for the first report of a single individual of Quercus suber which proved to be triploid (2n=3x=36). The rDNA physical mapping revealed several patterns: the dominant one is present in European and Asian Quercus subgenus Quercus, and in Castanea sativa and Castanea crenata, consisting of two 18S–25S rDNA loci (one subterminal major and one pericentromeric minor) and one 5S rDNA pericentromeric locus. In Fagus sylvatica and in Quercus sessilifolia, different patterns were observed: four terminal 18S–25S rDNA loci and two 5S rDNA pericentromeric loci in the former, and five 18S–25S rDNA loci (three terminal and two intercalary) and one 5S rDNA pericentromeric locus in the latter. In Castanea mollissima a distinct rDNA distribution pattern with two intercalary 18S–25S rDNA loci and two 5S rDNA was found. These findings suggest rDNA loci restructuring during Castanea evolution, and variability of 18S–25S loci between Quercus and Cyclobalanopsis subgenera.     

4 Phylogeny of the dasycladales (ulvophyceae,chlorophyta) based on analyses of nuclear‐encoded large subunit rDNA

The Dasycladales is an ancient order of tropical benthic marine green algae, unique in their radially arranged unicellular thalli and well‐preserved fossil record due to extensive calcification of the thallus. The inference of an accurate phylogeny for the Dasycladales is important in order to better understand stratigraphy, character evolution, and classification. Previous analyses (rbcL and 18S rDNA) suggested that the Family Acetabulariaceae is monophyletic, but that the Family Dasycladaceae is a basal paraphyletic assemblage. However, the two data sets disagreed regarding genus‐ and species‐level relationships within the Dasycladales. For example, the placement of the genera, Halicoryne, Bornetella and Cymopolia were incongruent. Given the conflicting results of these previous analyses, the current project examined a third highly conserved nuclear‐encoded gene, 26S rDNA. Aligned 26S rDNA sequences were analyzed with parsimony and model‐based methods and compared to previous results based on18S and rbcL sequences. Family‐level relationships based on 26S rDNA were congruent with previous studies: the Acetabulariaceae is monophyletic while the Dasycladaceae is paraphyletic. In addition, acetabulariacean genera are not monophyletic, suggesting that the presence of a corona inferior or calcification of gametes may not be appropriate to define genera. Within the Dasycladaceae, the basal position of Cymopolia is supported by 26S rDNA, a result congruent with rbcL and stratigraphy but not with 18S data. These results will be discussed in the context of morphological character evolution, fossil stratigraphy and family, tribal and generic relationships among these living algal fossils. Supported in part by NSF grant DEB‐0128977 to FWZ.     

Systematics and evolution of syllids (Annelida,Syllidae)

A large, combined phylogenetic analysis (including morphological and molecular data from 18S rDNA, 16S rDNA and cytochrome c oxidase subunit I), with the highest number of species and genera of Syllidae studied to date (213 terminals), is examined. The data were explored with different parameters and optimality criteria (parsimony, likelihood, and bayesian inference). The monophyly of Syllidae and most of the traditional subfamilies is supported. The subfamily Eusyllinae is polyphyletic, as currently delineated, but it is herein reorganized and its diagnosis modified to be a valid group. Additional well supported clades arise. The phylogenetic relationships of the well known and established genera, as well as several enigmatic genera (e.g. Anguillosyllis, Paraopisthosyllis and Parahaplosyllis), the position of which in syllid taxonomy was uncertain or dubious to date, are clarified. The results corroborate previous hypotheses about the evolution of the reproductive and brooding modes. Within Syllinae, the nature of the stolon is phylogenetically informative. The classification of the whole family is revised and discussed on the basis of this phylogenetic hypothesis. © The Willi Hennig Society 2011.     

Physical mapping of ribosomal RNA genes in peonies (Paeonia,Paeoniaceae) by fluorescent in situ hybridization: implications for phylogeny and concerted evolution

Physical maps of the 18S–5.8S–26S ribosomal RNA genes (rDNA) were generated by fluorescent in situ hybridization for five diploid Paeonia species, P. delavayi and P. rockii of section Moutan, and P. emodi, P. tenuifolia, and P. veitchii of section Paeonia. Of five pairs of mitotic chromosomes, rDNA loci were mapped near the telomeres of chromosomes 3, 4, and 5 of P. rockii and P. tenuifolia, chromosomes 2, 3, 4, and 5 of P. delavayi, and all five pairs of chromosomes of P. emodi and P. veitchii. Combining this information with the previously obtained rDNA maps of P. brownii and P. californica of section Oneapia, we hypothesized that the most recent common ancestor of extant peony species had three rDNA loci located on chromosomes 3, 4, and 5. Increase in number of rDNA loci occurred later in each of the three sections, and the increase from three to four loci represents a parallel gain of an rDNA locus on chromosome 2 in P. delavayi of section Moutan and P. brownii of section Oneapia. The increase in number of rDNA loci likely resulted from the translocation of rDNA repeats from chromosomes bearing rDNA loci to chromosomes without them; such translocation is probably facilitated by the telomeric location of rDNA loci. For allotetraploid peony species lacking polymorphism in sequences of the internal transcribed spacers (ITS) of rDNA, the rDNAs derived from divergent diploid parents may have been homogenized through concerted evolution among at least six rDNA loci in the allotetraploids. Chromosomal location of rDNA loci has a more substantial impact on the tempo of concerted evolution than the number of loci.