Genetic Divergence of Far-Eastern Dace Species Belonging to the Genus Tribolodon (Pisces, Cyprinidae) and Closely Related Taxa

Based on a biochemical–genetic approach, heterozygosity and divergence of structural genes at 30 enzyme loci were analyzed in six dace species. In addition, intra- and interspecific divergence of gene expression was analyzed based on a sample of 12 to 15 loci. Mean heterozygosities per individual varied as follows: Tribolodon species, H _obs = 0.007 ± 0.007 and H _exp = 0.007 ± 0.007; T. ezoe, H _obs = 0.045 ± 0.016 and H _exp = 0.067 ± 0.029. Several variants of genetic distances were estimated. Standard Nei's distances (D _N) varied from 0.145 to 0.284 in four dace species studied. As related to Tribolodon dace species, the following genetic distances were obtained for two members of other genera:Pseudaspius leptocephalus, D _N = 0.269; Leuciscus waleckii, D _N = 0.769. Based on the distance matrices, different clustering algorithms were realized. The main feature shared by different dendrograms was a separate position of the cluster joining Far-Eastern dace species, to whichP. leptocephalus and L. waleckii are successively added. Among the species studied, the proportion of loci similar by expression (E) varied from 87 to 100%. The greatest difference was found between landlocked and landlocked ecotypes of T. hakonensis, E = 67%. The following conclusions can be made: (1) Four studied species of the genus Tribolodon are rather well genetically differentiated. Diagnostic loci are available. (2) A nominal dace species, T. species, should be considered the fourth unambigous species of this genus, which is confirmed by its recent zoological acceptance of this species. (3) The origin and divergence of dace species belonging to the genus Tribolodon are relatively late (1 to 3 Myr ago) historical events. (4) Taxonomically, the genus Tribolodon belong to the tribe Pseudaspinini together with P. leptocephalus, which is confirmed by genetic data. (5) Data on heterozygosity and the divergence of structural and regulatory elements of genome, along with the proposed scheme of speciation types, suggest the following speciation modes for the species studied: for four species, adaptive divergence and for two species, genetic transformation.     

Variation among tripsacum populations of Mexico and Guatemala

Seven species of the genusTripsacum, one with a well marked subspecies, are indigenous to Mexico and Guatemala. Two diploids,T. zopilotense andT. maizar, are restricted to western and southwestern Mexico. The typical diploid form of a third species,T. latifolium, occurs in south central and eastern Guatemala; atypical tetraploid forms of this species are found in western Mexico. Four tetraploids,T. dactyloides, T. dactyloides ssp.hispidum, T. lanceolatum, andT. pilosum, have ranges extending from northwestern Mexico southeastward into Guatemala. The seventh species is the highly sterile tetraploid,T. laxum, of doubtful occurrence in the wild. It is readily propagated vegetatively and has been widely distributed in Latin America and the West Indies as a forage plant. Field studies of the range of variation in 80 Mexican and Guatemalan populations included an evaluation of 16 definitive morphological characteristics from an average of approximately six individuals of each population. Seventy-three of the 80 populations were allopatric, and of these, 50 were classed as typical, 13 as atypical, and ten as intermediates. Thirty-nine of the 50 populations classed as typical were tetraploid, and 11 were diploid. Of the 23 atypical and intermediate populations, 17 were tetraploid and six were diploid. Fifty-eight tetraploid populations, which included typical, atypical, and intermediate forms ofT. dactyloides, T. dactyloides ssp.hispidum, T. lanceolatum, T. pilosum, andT. latifolium, comprised an inclusive intergrading series having different combinations of characteristics distinguishing the two very dissimilar diploids,T. mizar andT. zopilotense. This series was interpreted as support for the hypothesis of Randolph & Hernández (1950), that the tetraploid populations originated as alloploid derivatives of these or closely related diploid species. The occurrence in some of the tetraploid populations of characteristics not seen in either of the putative parental species was noted, and the possibility that other taxa also might have been involved in their origin is under investigation. In addition to the 73 allopatric populations included in this survey there were seven sympatric and mixed associations of diploid and tetraploid taxa. Among these were hybrids with various combinations of the characteristics differentiating taxa of the associated populations. These hybrids effectively obscured differences between taxa, thus creating a syngameon complex from which genetic recombinants were observed to have spread into recently disturbed habitats of neighboring areas. From such direct evidence, and the existing interrelationships among allopatric and sympatric populations, it was concluded that the origin of the Mexican and Guatemalan tetraploidTripsacum species and various atypical and intermediate variants, has involved, and is continuing to involve, alloploid recombinants of diploid species and syngameon complexes, of which those encountered in this survey are examples.     

Analysis of mitochondrial DNA: Taxonomic and phylogenetic relationships in two fish taxa (Pisces: Mugilidae and Cyprinidae)

To solve some systematic questions as well as to study genetic variability and evolutionary relationships in two groups of fish belonging to the Mugilid (Mugilidae) and Cyprinid (Cyprinidae) families, we have used restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) fragments amplified in polymerase chain reaction. The analysis of three mtDNA fragments of 7220 bp total length of six Mugilid species has shown that Mediterranean Liza aurata, L. ramada, L. saliens, and Chelon labrosus form a common cluster, L. aurata and C. labrosus being the closest relatives, whereas L. haematocheilus (syn. C. haematocheilus) of the Sea of Japan forms a sister group to the Mediterranean cluster. It was found that Chelon and Liza genera are paraphyletic, and therefore their division into two genera is unnatural and they should be synonymized. According to priority, Liza species should be ascribed to Chelon genus. Mugil cephalus is the most distant compared to the rest of the species studied. The level of genetic divergence between allopatric samples of M. cephalus from the Sea of Japan and the Mediterranean Sea has proved to be very high—4.5% of nucleotide substitutions. The analysis of four mtDNA fragments of 9340 bp total length of six Cyprinid species has shown that L. waleckii is the most genetically distant. Pseudaspius leptocephalus is a sister group to Tribolodon species. All Tribolodon species form a common cluster with T. sachalinensis as a root. The remaining species form two branches, one of which includes T. nakamurai and T. brandtii, another one combines T. hakonensis and a new form of Tribolodon revealed that is close to T. hakonensis by its mtDNA (2.4% of nucleotide substitutions). This new form might be an independent species. Published in Russian in Biokhimiya, 2007, Vol. 72, No. 12, pp. 1651–1658.     

Chromosome relationships between Lolium and Festuca (Gramineae)

With a view to eclucidating chromosome relationships between Lolium perenne (Lp), L. multiflorum (Lm) and Festuca pratensis (Fp), chromosome pairing in different diploid (2n=14), auto-allotriploid (2n=3x=21), trispecific (2n=3x=21), amphidiploid (2n=4x=28) and auto-allohexaploid (2n=6x=42) hybrids between them was analysed. At all these levels of ploidy there was very good chiasmate pairing between the chromosomes of the three species and, on the whole, there was little evidence of preferential pairing of the chromosomes of a particular species in the triploid, tetraploid and hexaploid hybrids. A critical test for this also came from the synaptic ability of the chromosomes of the single genome with those of the duplicated genome in the auto-allotriploids which formed predominantly trivalents with 2, 3 or even 4 chiasmata. Moreover, the homology between the Lp and Lm chromosomes seems strong enough to pass the discrimination limits of the B-chromosomes which do not suppress homoeologous pairing in the Lp LmLm triploid and LpLm diploid hybrids. — The triploids having two genomes of a Lolium species and one of F. pratensis had some male and female fertility which suggested genetic compatibility of the parental chromosomes resulting, presumably, in compensation at the gametic level. Also, the occurrence of comparable chiasma frequencies in the auto-allotriploids and trispecific hybrids showed that they were not markedly affected whether two doses of one genome and one of the other or all the three different genomes from the three species were present. From the trend of chromosome pairing in all these hybrids it is concluded that there is little structural differentiation between the chromosomes of the three species, no effective isolation barrier to gene-flow between them, and that they are closely related phylogenetically, having possibly evolved from a common progenitor. Taxonomic revision of the two Lolium species is suggested.     

<Emphasis Type="Italic">Tamarix</Emphasis> (Tamaricaceae) hybrids: the dominant invasive genotype in southern Africa

Hybridization is regarded as a rapid mechanism for increasing genetic variation that can potentially enhance invasiveness. Tamarix hybrids appear to be the dominant genotypes in their invasions. Exotic Tamarix are declared invasive in South Africa and the exotic T. chinensis and T. ramosissima are known to hybridize between themselves, and with the indigenous T. usneoides. However, until now, it was not known which species or hybrid is the most prevalent in the invasion. With a biocontrol programme being considered as a way of suppressing the alien Tamarix populations, it is important to document the population genetic dynamics of all species in the region. This investigation sought to identify Tamarix species in southern Africa and their hybrids, describe their population structure, and reveal the geographic origin of the invasive species. To achieve this, nuclear Internal Transcribed Spacer (ITS) sequence data and the multilocus Amplified Fragment Length Polymorphisms (AFLPs) markers were used. Phylogenetic analysis and population genetic structure confirmed the presence of three species in South Africa (T. chinensis, T. ramosissima and T. usneoides) with their hybrids. The indigenous T. usneoides is clearly genetically distant from the alien species T. chinensis and T. ramosissima. Interestingly, the Tamarix infestation in South Africa is dominated (64.7 %) by hybrids between T. chinensis and T. ramosissima. The exotic species match their counterparts from their places of origin in Eurasia, as well as those forming part of the invasion in the US.     

Three new species ofTrisetum (Poaceae) from China

Three new species of the genusTrisetum from the province Yunnan are described:Trisetum lautum, T. debile andT. yunnanense which belong toTrisetum flavescens-group.     

Chromosome numbers in callirhoe (Malvaceae)

Forty-four chromosome counts from the North American genusCallirhoe are reported, including first-recorded counts ofC. alcaeoides, C. digitata, C. bushii, C. triangulata, andC. involucrata var.tenuissima. Information concerning chromosome numbers from present and previous reports is summarized and evaluated. Observations are presented on meiosis for the genus in general, for male sterile individuals of gynodioecious species, and for selected F₁ hybrids. Pollen fertility data are recorded for the latter. Chromosomally three species groups are recognized: an exinvolucellate, diploid species group withn=14; an involucellate, tetraploid and octoploid species pair,n=28 and 56; and an involucellate, diploid and tetraploid species group withn=15 and 30. Intrageneric relationships and those within the tribe Malveae subtribe Malvinae are discussed.     

Die GattungTeutonica Schröder 1991 (Gastropoda) aus dem Dogger Deutschlands und Nordwestpolens

Up to now the genusTeutonica has only been known by its type species. Four species and two subspecies are related to it herein; two species and one subspecies are new:T. verrucosa, T. procera andT. gramanni nodosa. Zygopleura rectecostata Walther is based on poorly preserved juvenile shells of aTeutonica species — therefore its specific identity will remain doubtful while its generic placement is clear. The genusTeutonica is known from the Bajocian and Bathonian. It was formerly related to the families Cerithiopsidae or Zygopleuridae. Here the genus is placed with the Polygyrinidae becausePolygyrina andTeutonica are very similar regarding teleoconch shape, course of the growth lines, and the protoconch shape.     

Phylogenetic relationships and natural hybridization in Triadica inferred from nuclear and chloroplast DNA analyses

Triadica (Euphorbiaceae) is a small genus endemic to East Asia and Southeast Asia, consisting of three species differentially adapted to heterogeneous habitats. To date, the phylogenetic relationships of this genus have not been resolved, and there has been no evidence for interspecific hybridization in Triadica. In this study, we sequenced the nrITS regions, two nuclear genes and a chloroplast gene to reconstruct the molecular phylogeny of Triadica and to test the hypothesis of natural hybridization between Triadica sebifera and Triadica cochinchinensis, and between T. sebifera and Tridica rotundifolia. Phylogenetic analysis showed that T. sebifera diverged first within this genus, and T. cochinchinensis and T. rotundifolia were sister species. Both of the two putative hybrids show chromatogram additivity at each of the two nuclear genes, providing convincing evidence for natural hybridization between T. sebifera and T. cochinchinensis, and between T. sebifera and T. rotundifolia. The chloroplast gene sequences of both hybrids were identical with that of T. sebifera, suggesting that T. sebifera was the maternal parent of the two hybrids. This is the first report of natural hybridization in Triadica, and the hybrids identified in this study should be a good starting point for further hybridization-based breeding in T. sebifera.     

The problem of carotenoid biosynthesis in the taxonomy of genera Rhodotorula and Rhodosporidium

This report presents results in the composition of major carotenoids of various coloured mutants of the genusRhodotorula and of mating types of the genusRhodosporidium. The separation of carotenoid intermediates was carried out by thin layer chromatography using Silufol 254 Kavalier and the determination of eluated spots by spectrophotometry. There was found no difference in carotenoid composition of both mating typesa and α of individual species of the genusRhodosporidium. The vegetative and sexual reproduction ofRhodotorula andRhodosporidium can be separated from the carotenogenesis using 10^?4 mol diphenylamine. It was concluded that lycopene could be the intermediate to mono- and dicyclic carotenoids; in the case of partial inhibition of the dehydrogenation step the direct cyclization of neurosporene to β-zeacarotene can be expected. An unknown compound, probably lycopersene was found and was considered to be the precursor of phytoene. Phytoene and phytofluene were proved in all studied samples. Nutritional conditions (vitamins, sulfur amino acids, etc.) are able to shift the ratios between major carotenoids. Rhodotorula aurantiaca strains were observed to be auxotrophic mutants of various characters and the existence of this species as independent one, was denied.     

The genus anemia (Schizaeaceae) in Mexico

The fern genusAnemia is represented in Mexico by 21 species and hybrids, of which five are here described as new:A. familiaris, A. multiplex. A. ×paraphyllitidis. A.×recondita andA. semihirsuta. Hybridization is frequent, resulting in both sterile and fertile hybrids, and has probably led to much recent speciation in the genus, including presumably sexual polyploids up to possibly the tetrakaidecaploid level.     

No reduction of hatching rates among F1 hybrids of naturally hybridizing three Far Eastern daces,genus <Emphasis Type="Italic">Tribolodon</Emphasis> (Cypriniformes,Cyprinidae)

Egg hatching rates of F1 hybrids among three fishes, Japanese dace Tribolodon hakonensis, Pacific redfin T. brandtii, and rosyface dace T. sachalinensis, were compared with pure crosses. They are highly divergent (diverged 10–20 million years ago) but naturally hybridizing. Although crosses involving female rosyface dace were not available, hatching success was high among all combinations of hybrids (76 ± 23%) and comparable to pure crosses (86 ± 8%), implying ecological or genetic isolation mechanisms maintaining each species in later life stages.     

Unreduced gamete formation in wheat × <Emphasis Type="Italic">Aegilops</Emphasis> spp. hybrids is genotype specific and prevented by shared homologous subgenomes

Key message

The presence of homologous subgenomes inhibited unreduced gamete formation in wheat × Aegilops interspecific hybrids. Unreduced gamete rates were under the control of the wheat nuclear genome.

Abstract

Production of unreduced gametes is common among interspecific hybrids, and may be affected by parental genotypes and genomic similarity. In the present study, five cultivars of Triticum aestivum and two tetraploid Aegilops species (i.e. Ae. triuncialis and Ae. cylindrica) were reciprocally crossed to produce 20 interspecific hybrid combinations. These hybrids comprised two different types: T. aestivum × Aegilops triuncialis; 2n = ABDU^tC^t (which lack a common subgenome) and T. aestivum × Ae. cylindrica; 2n = ABDD^cC^c (which share a common subgenome). The frequency of unreduced gametes in F₁ hybrids was estimated in sporads from the frequency of dyads, and the frequency of viable pollen, germinated pollen and seed set were recorded. Different meiotic abnormalities recorded in the hybrids included precocious chromosome migration to the poles at metaphase I and II, laggards in anaphase I and II, micronuclei and chromosome stickiness, failure in cell wall formation, premature cytokinesis and microspore fusion. The mean frequency of restitution meiosis was 10.1 %, and the mean frequency of unreduced viable pollen was 4.84 % in T. aestivum × Ae. triuncialis hybrids. By contrast, in T. aestivum × Ae. cylindrica hybrids no meiotic restitution was observed, and a low rate of viable gametes (0.3 %) was recorded. This study present evidence that high levels of homologous pairing between the D and D^c subgenomes may interfere with meiotic restitution and the formation of unreduced gametes. Variation in unreduced gamete production was also observed between T. aestivum × Ae. triuncialis hybrid plants, suggesting genetic control of this trait.

     

Taxonomic revision of the Kimmeridgian (Upper Jurassic) genusMesosimoceras (Ammonoidea) and institution of the new genusPresimoceras (Ammonitina,Idoceratinae)

Presimoceras is a new genus of Idoceratinae. The biostratigraphical range ofPresimoceras is limited to theStrombecki, Divisum and lower part of theAcanthicum Zone within the Kimmeridgian (in the Southern European sense). The genusMesosimoceras (Idoceratinae) was instituted by Spath (1925), withSimoceras cavouri Gemmellaro as type species; this genus is here emended with the institution ofPresimoceras n. gen. The species groupcavouri-risgoviense is preserved in the emended genusMesosimoceras, while the groupherbichiludovicii-teres is accommodated inPresimoceras on account of the radical and numerous differences and the stratigraphical gap betweenMesosimoceras andPresimoceras. As type species of the new genusAmmonites nodulatus Quenstedt is designated. The new genus is here subdivided into three groups of species:herbichi, ludovicii andteres. Phylogenetically,Presimoceras is derived fromPassendorferia, Mesosimoceras fromNebrodites.     

Structural chromosome differentiation between Triticum timopheevii and T. turgidum and T. aestivum

 Chromosome pairing at metaphase-I was analyzed in F₁ hybrids among T. turgidum (AABB), T. aestivum (AABBDD), and T. timopheevii (A^tA^tGG) to study the chromosome structure of T. timopheevii relative to durum (T. turgidum) and bread (T. aestivum) wheats. Individual chromosomes and their arms were identified by means of C-banding. Homologous pairing between the A-genome chromosomes was similar in the three hybrid types AA^tBG, AA^tBGD, and AABBD. However, associations of B-G were less frequent than B-B. Homoeologous associations were also observed, especially in the AA^tBGD hybrids. T. timopheevii chromosomes 1A^t, 2A^t, 5A^t, 7A^t, 2G, 3G, 5G, and 6G do not differ structurally from their counterpart in the A and B genomes. Thus, these three polyploid species inherited translocation 5AL/4AL from the diploid A-genome donor. Chromosome rearrangements that occurred at the tetraploid level were different in T. turgidum and T. timopheevii. Translocation 4AL/7BS and a pericentric inversion of chromosome 4A originated only in the T. turgidum lineage. The two lines of T. timophevii studied carry four different translocations, 6A^tS/1GS, 1GS/4GS, 4GS/4A^tL, and 4A^tL/3A^tL, which most likely arose in that sequence. These structural differences support a diphyletic origin of polyploid wheats. Received: 15 June 1998 / Accepted: 19 August 1998     

A new species ofTragopogon from the Iraqi Kurdistan

A new species of the genusTragopogon (T. kurdistanicum) has been described from Iraq.