Karyotypic variation in bisexual species and pseudogamous forms of the planthopper genus Ribautodelphax (Homoptera,Delphacidae)

Chromosome numbers of Ribautodelphax collinus. R. angulosus, R. pungens, R. imitans, R. fanari, R. pallens, R. albostriatus, and of four undescribed species, provisionally indicated as Taxon 1 to 4, were determined. The chromosome number of all species was found to be 2n=30 (14II+XX-XO); however, in several species some females with 2n=31 or 32 also occurred. One female of R. collinus and one of Taxon 1 possessed eggs with 16 bivalents and one egg with 32 bivalents. One female of R. pungens contained only tetraploid eggs. Pseudogamous triploid females occurred in populations of R. pungens and Taxon 4. Their chromosome numbers ranged from 3n=40 to 46 in R. pungens and 3n=41 to 45 in Taxon 4. In several pseudogamous females from two R. pungens populations, eggs with 45 univalents and with various numbers of univalents, bivalents and trivalents were found. The mode of origin of pseudogamous triploid females is discussed and it is concluded that karyotypic data are consistent with an autopolyploid origin.     

Distribution and Cytogenetic Features of Triploid Males of Crucian Carp in Azov Basin

When studying uni-bisexual crucian carp (Carassius auratus gibelio) populations in the Azov basin in 1995–2000, we found triploid males, which constituted 2.5%, on average, of the total numbers of studied samples. The areas of nuclei of erythrocytes of triploid males were, on average, 1.35 times those in diploid males. At the same optical density of DNA, the sizes of mature spermatozoon heads in triploid males were, on average, 1.8 times smaller than in diploid males, as follows from the data obtained in summer 1996. The results of similar studies carried out during the period of natural spawning activity in 1997–1999 suggest that the sizes of spermatozoon heads in triploid males were, on the contrary, 1.5 those in diploid males. Triploid males were characterized by mosaicism of spermatozoon sizes and chromosome mosaicism in somatic cells. Electrophoretic analysis for the locus of transferrin confirmed the triploid status of this genetic group. The results of comparative crosses of crucian carps with different ploidy suggest a high fertilizing capacity of triploid males, as well as normal viability of their progenies. A distinct positive correlation (r = 0.73) was found between the numbers of triploid females and triploid males in mixed di-triploid populations. No significant correlation was found between males and females within di- and triploid forms.     

Can obligate apomixis and more stable reproductive assurance explain the distributional successes of asexual triploids in Hieracium alpinum (Asteraceae)?

• Although reproductive assurance has been suggested to be one of the most important factors shaping the differential distributional patterns between sexuals and asexuals (geographic parthenogenesis), it has only rarely been studied in natural populations of vascular plants with autonomous apomixis. Moreover, there are almost no data concerning the putative relationship between the level of apomictic versus sexual plant reproduction on one hand, and reproductive assurance on the other.
• We assessed the level of sexual versus apomictic reproduction in diploid and triploid plants of Hieracium alpinum across its distributional range using flow cytometric analyses of seeds, and compared the level of potential and realized seed set, i.e. reproductive assurance, between the two cytotypes under field and greenhouse conditions.
• Flow cytometric screening of embryos and endosperms of more than 4,100 seeds showed that diploids produced solely diploid progeny sexually, while triploids produced triploid progeny by obligate apomixis. Potential fruit set was much the same in diploids and triploids from the field and the greenhouse experiment. While in the pollination‐limited environment in the greenhouse apomictic triploids had considerably higher realized fruit set than sexual diploids, there was no significant difference between cytotypes under natural conditions. In addition, sexuals varied to a significantly larger extent in realized fruit set than asexuals under both natural and greenhouse conditions.
• Our results indicate that triploid plants reproduce by obligate apomixis, assuring more stable and predictable fruit reproduction when compared to sexual diploids. This advantage could provide apomictic triploids with a superior colonisation ability, mirrored in a strong geographic parthenogenesis pattern observed in this species.

     

Cytogenetic studies of Poecilia (Pisces)

Natural populations of triploid females resembling the gynogenetic teleost, Poecilia formosa (Girard), occur in northeastern Mexico where they intermingle with diploid populations of this species and the members of congeneric bisexual species such as P. mexicana or P. latipinna. Mitotic configurations from gill epithelial cells show 46 chromosomes for the diploid fishes, but 69 chromosomes for members of the triploid clones associated with P. formosa. Triploid females have erythrocytes that are significantly larger than those from diploid specimens and also show a roughly 50% elevation in the average DNA content of their somatic nuclei. Similar analyses of two functionally incompetent males of P. formosa, of a number of bisexual F₁ and F₂ hybrid offpsring from P. latipinna x P. mexicana, and of females from several other poeciliid species consistently show only diploid DNA levels and somatic chromosome complements where 22N=46. Demonstration of cytogenetic criteria by which females from triploid clones may be clearly distinguished from sympatric diploid specimens of P. formosa or P. mexicana leaves unresolved, for the present, problems of an appropriate systematic designation for natural populations of triploid gynogenetic fishes. The role of sympatric speciation in the evolution of poeciliid genomes is discussed in terms of alternative mechanisms to account for the persistence in nature of a vertebrate triploid of hybrid origin.This work was supported by grants from the National Science Foundation (GB 7393) and from the U.S. Public Health Service (GM 14644).Recipient of a Research Career Development Award from the U.S. Public Health Service (1 K3 GM 3455).     

Contrasting patterns of spatial genetic structure of diploid and triploid populations of the clonal aquatic species,<Emphasis Type="Italic">Butomus umbellatus (Butomaceae)</Emphasis>, in Central Europe

Genetic diversity in a sample of an aquatic plantButomus umbellatus from 37 localities in Czechia and Slovakia was studied by analyzing six polymorphic loci in three enzymatic systems (SKDH, PGD and AAT). Diversity among ramets was low in eight populations with relatively extensive sampling (only one population possessed more than one multilocus genotype), suggesting high clonality of reproduction in these populations. However, among-population diversity was high: G = 0.782 and 0.881 for the samples of diploid and triploid populations, respectively. Heterozygosity of individual plants averaged over variable loci was also high: H = 0.554 for diploids and 0.453 for triploids. Genetic differentiation among populations was additionally studied using cluster analysis. Several populations of diploids clustered separately from all other populations, whereas another group of diploid populations clustered with some triploid populations, indicating the possibility of relatively recent, probably multiple origin of these triploid populations from their diploid progenitors. Association between matrices of Nei’s genetic distances among populations from different localities and matrices of geographic distances among these localities revealed highly significant correlation for the sample of diploid populations (r = 0.60,P < 0.001) but no significant correlation for the sample of triploid populations (r = 0.02,P = 0.593). These results indicate a spatial structure of diploid populations in accordance with the isolation by distance model, and a random distribution of genotypes among triploid populations ofB. umbellatus.     

三倍体丹参杂交种的花粉形态研究

三倍体丹参是以二倍体丹参为父本、人工染色体加倍的四倍体白花丹参为母本杂交选育的杂交种。为深入了解三倍体丹参花粉的特性,以及为三倍体种质利用提供孢粉学依据,该文以二倍体丹参为对照,研究了三倍体丹参杂交种花粉的形态变异规律。利用光学显微镜和扫描电镜对二倍体和三倍体丹参的花粉萌发沟、外壁纹饰、花粉粒形状等特征进行了显微和超微形态观察,综合进行了花粉形态差异比较,并对花粉大小和形状数据进行了差异显著性分析和正态检验。结果表明:(1)二倍体丹参为6沟花粉,三倍体花粉萌发沟有6沟和8沟两种类型,沟内疣状颗粒分布不匀,出现畸形萌发沟。(2)二倍体和三倍体花粉外壁均为网状雕纹。二倍体花粉网眼内具多个多边形穿孔,穿孔大; 6沟和8沟两种类型的三倍体花粉网眼无穿孔或仅有几个小穿孔,6沟和8沟花粉的外壁雕纹相同。(3)三倍体花粉的极轴长(P)和赤道宽(E)均值显著小于二倍体花粉,花粉大小呈偏正态分布,P*E的差异系数大于二倍体花粉,且有极值存在。三倍体和二倍体丹参的萌发沟和雕纹存在差异,而花粉形状差异不显著。综上结果表明三倍体丹参花粉在倍性效应和杂合性的双重影响下发生了形态变异,且有多种形态变化。     

Triploid bumblebees indicate a direct cost of inbreeding in fragmented populations

Hymenopteran species with single-locus complimentary sex-determination (sl-CSD) face an additional cost of inbreeding because of a loss of diversity at the sex-determining locus. Laboratory studies of a range of Hymenoptera have found that a small percentage of diploid males produce viable diploid sperm, and that if these males mate, then the resultant females produce triploid offspring that are sterile. Here, we use microsatellite markers to determine the frequency of triploid individuals of Bombus muscorum and B. jonellus in a model island system. Triploids were found in populations of both species. Observed triploid frequencies of up to 8% were detected, and estimated total frequencies peaked at 20% with respect to normal diploid workers. For both species, triploid frequency was negatively correlated with surrogates of population size, providing direct evidence for inbreeding in small populations. Populations limited to <～15 km(2) of suitable habitat were particularly likely to harbour triploids. Estimated total triploid frequencies were higher in B. muscorum than in B. jonellus, perhaps due to the greater dispersal range of the latter species. Implications for the conservation of rare social hymenopterans are discussed.     

Mode of hybridogenesis and habitat preferences influence population composition of water frogs (Pelophylax esculentus complex,Anura: Ranidae) in a region of sympatric occurrence (western Slovakia)

Coexistence of sperm‐dependent asexual hybrids with their sexual progenitors depends on genetic and ecological interactions between sexual and asexual forms. In this study, we investigate genotypic composition, modes of hybridogenetic gametogenesis and habitat preferences of European water frogs (Pelophylax esculentus complex) in a region of sympatric occurrence. Pelophylax esculentus complex comprises parental species P. ridibundus and P. lessonae, whose primary hybridization leads to hybridogenetic lineages of P. esculentus. Hybrids clonally transmit one parental genome and mate with the other parental species, forming a new generation of hybrids. In the region of western Slovakia, we found syntopic occurrence of diploid and triploid hybrids with P. lessonae, syntopic occurrence of all three taxa as well as the existence of pure P. ridibundus populations. All triploid hybrids were exclusively male possessing one ridibundus and two different lessonae genomes (RLL). Sex ratio in diploid hybrids was substantially female‐biased. Irrespective of the population composition, diploid hybrids excluded the lessonae genome from their germ line and produced ridibundus gametes. Contrarily, RLL males unequivocally eliminated the ridibundus genome and produced diploid lessonae sperms. Perpetuation of RLL males in studied populations is most likely achieved by their mating with diploid hybrid females. The composition of water frog populations is also shaped by taxon‐specific habitat preferences. While P. ridibundus preferred larger water bodies (gravelpits, fishery ponds, dead river arms), P. lessonae was most frequently found in marshes and smaller sandpits. Pelophylax esculentus occupied predominately similar habitats as its sexual host P. lessonae.     

Multiple supernumerary chromosomes in the pseudogamous parthenogenetic flatworm Polycelis nigra: lineage markers or remnants of genetic leakage?

Polycelis nigra is a free-living simultaneous hermaphroditic flatworm that has amphimictic and pseudogamous parthenogenetic biotypes. Sexual individuals are always diploid (2n = 16) and pseudogamous parthenogens are polyploid (usually triploid). Two types of supernumerary chromosomes are found in parthenogens, those resembling autosomes ("A-like") and typical B chromosomes, both of which reach frequencies in populations of close to 100%. Experiments measuring the transmission rates of the B chromosomes indicated that they are potentially inherited via the male line, escaping expulsion by pseudogamous parthenogenesis. This study used the C-banding technique to demonstrate (i) that there is a single morphologically distinct B chromosome (B1) and (ii) that there are two "A-like" chromosomes that can be considered B chromosomes (B2 and B3) and which are not simple polysomics of one of the eight autosomes. As there is no genetic exchange between pseudogamous parthenogenetic lineages, two different individuals carrying a similar B morph must either have received it through common ancestry (a lineage marker) or have acquired it horizontally from another parthenogenetic lineage (leakage). C-banding further revealed intra-individual heteromorphy for band regions on chromosomes 5 and 8. This supports the karyotypic observation that oogenesis is preceded by premeiotic chromosome doubling followed by pairing of replicate homologues.     

The gynogenetic reproduction of diploid and triploid hybrid spined loaches (<Emphasis Type="Italic">Cobitis</Emphasis>: Teleostei), and their ability to establish successful clonal lineages—on the evolution of polyploidy in asexual vertebrates

Polyploidisation is assumed to have played a significant role in the evolution of hybrid asexual lineages. The virtual absence of natural asexual systems in which more than a single ploidy level successfully establishes successful independent clonal lineages is generally explained by the strong effects of polyploidisation on fitness. Experimental crosses were made between diploid and triploid asexual Cobitis elongatoides × C. taenia hybrids (female) and both parental spined loach species (male). Genotyping of the progeny using allozymes and multilocus DNA fingerprinting, along with flow cytometric measurement of ploidy level, demonstrated the occurrence of gynogenetic reproduction in both female biotypes. The incorporation of the sperm genome occurred in some progeny, giving rise to a higher ploidy level, but the rate of polyploidisation differed significantly between the diploid and triploid females. These outcomes are consistent with the existence of developmental constraints on tetraploidy, which determine the rarity of tetraploids in natural populations. No cases of ploidy level reduction were observed. Since diploid and triploid hybrid populations occur where the lack of potential progenitor excludes the possibility of de novo origin, it is probable that both diploid and triploid females can establish successful clonal lineages. Spined loaches represent a unique example, among asexual vertebrates, where more than one ploidy level can establish persistent clonal lineages, which are reproductively independent of one another.     

Hybridization studies in the planthopper genus Ribautodelphax (Homoptera,Delphacidae)

Seven known Ribautodelphax species and four recently discovered taxa were crossed. Forty-three percent of the interspecific crosses were successful. Interspecific crosses generally resulted in low numbers of hybrids. In some combinations prolonged larval development of the hybrid males was observed. Backcrosses showed that both male and female hybrids were fertile. Reproductive isolation was mainly maintained by premating barriers. Insemination tests revealed that prolonged confinement of males and females lowered mating thresholds. The taxonomic status of the known species and new taxa was shown to be in need of revision. No indications for a hybrid origin of the pseudogamous triploid Ribautodelphax females were found.     

Life‐history traits of the Whiting polyploid line of the parasitoid Nasonia vitripennis

In hymenopterans, males are normally haploid (1n) and females diploid (2n), but individuals with divergent ploidy levels are frequently found. In species with ‘complementary sex determination’ (CSD), increasing numbers of diploid males that are often infertile or unviable arise from inbreeding, presenting a major impediment to biocontrol breeding. Non‐CSD species, which are common in some parasitoid wasp taxa, do not produce polyploids through inbreeding. Nevertheless, polyploidy also occurs in non‐CSD Hymenoptera. As a first survey on the impacts of inbreeding and polyploidy of non‐CSD species, we investigate life‐history traits of a long‐term laboratory line of the parasitoid Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) (‘Whiting polyploid line’) in which polyploids of both sexes (diploid males, triploid females) are viable and fertile. Diploid males produce diploid sperm and virgin triploid females produce haploid and diploid eggs. We found that diploid males did not differ from haploid males with respect to body size, progeny size, mate competition, or lifespan. When diploid males were mated to many females (without accounting for mating order), the females produced a relatively high proportion of male offspring, possibly indicating that these males produce less sperm and/or have reduced sperm functionality. In triploid females, parasitization rate and fecundity were reduced and body size was slightly increased, but there was no effect on lifespan. After one generation of outbreeding, lifespan as well as parasitization rate were increased, and a body size difference was no longer apparent. This suggests that outbreeding has an effect on traits observed in an inbred polyploidy background. Overall, these results indicate some phenotypic detriments of non‐CSD polyploids that must be taken into account in breeding.     

MicroRNA expression changes following synthesis of three full-sib <Emphasis Type="Italic">Populus</Emphasis> triploid populations with different heterozygosities

Key message

Through high-throughput sequencing, we compared the relative expression levels of miRNA in three full-sib Populus triploid populations with that in their parents and one diploid hybrid population. We found similar numbers of miRNAs differentially expressed between the parents and the four progeny hybrid populations. In addition, unbalanced parental expression level dominance of miRNAs were found in the three allotriploid and interspecific hybrid populations, which may reprogram gene expression networks and contribute to the growth of Populus hybrids. These results indicated that hybridization has a great impact on the miRNA expression variation in the newly synthesized Populus triploid and diploid hybrid populations. However, we also found no significant differences in miRNA expression among one diploid and three triploid hybrid populations, hinting that miRNA abundances do not increase with the genome content. No dosage effect of miRNA expression could lead to dosage-dependent negative effects on target genes and their downstream pathway in polyploids. We speculate that polyploids may gain advantages from the slight decrease in miRNA regulation, suggesting an important molecular mechanism of polyploid advantage.

Abstract

Hybridization with three types of induced 2n gametes transmitted different parental heterozygosities has been proven as an efficient method for Populus triploid production. Several researches have shown that miRNA could be non-additively expressed in allopolyploids. However, it is still unclear whether the non-additively expressed miRNAs result from the effect of hybridization or polyploidization, and whether a dose response to the additional genomic content exists for the expression of miRNA. Toward this end, through high-throughput sequencing, we compared the expression levels of miRNA in three full-sib Populus triploid populations with that in their parents and one interspecific hybrid population. We found similar numbers of miRNAs differentially expressed between the parents and the four progeny hybrid populations. Unbalanced parental expression level dominance of miRNAs were found in the three triploid and diploid hybrid populations, which may reprogram gene expression networks and affect the growth of Populus hybrids. These results indicated that hybridization has a great impact on the miRNA expression variation in the newly synthesized Populus triploid and diploid hybrid populations. However, we also found no significant differences in miRNA expression among the three triploid populations and the diploid hybrid population. No dosage effect of miRNA expression could lead to dosage-dependent negative effects on target genes and their downstream pathway in polyploids. We speculate that polyploids may gain advantages from the decrease in miRNA negative regulation, suggesting an important molecular mechanism of polyploid advantage.

     

Ploidy distribution and DNA content variations of <Emphasis Type="Italic">Lonicera caerulea</Emphasis> (Caprifoliaceae) in Japan

Ploidy level and geographical distribution were investigated in Japanese Lonicera caerulea L. Flow cytometric analysis revealed the presence of DNA diploid and DNA tetraploid plants in Japan. Chromosome observation confirmed that diploid and tetraploid plants showed 2n = 2x = 18 and 2n = 4x = 36, respectively. The DNA diploid populations were found only in lowland mires, Betsukai, Bekanbeushi, Kushiro and Kiritappu located in eastern Hokkaido. On the other hand, DNA tetraploid populations were distributed in a wide area of Hokkaido, and mainland of Japan. The habitats of DNA tetraploid plants were lowland to alpine region. The DNA content measurement with flow cytometry revealed significant differences in the relative DNA contents among DNA tetraploid populations. The relative DNA content within DNA tetraploid populations varied 1.157-fold at maximum, and might correlate with altitude indicating that DNA contents were smaller as altitude increases. The wide area of distribution in various environments of DNA tetraploid plants suggested the adaptability of the tetraploid plants. Although diploid and tetraploid populations were found, no triploid was detected, indicating crossing difficulty between diploid and tetraploid as confirmed by crossing experiment.     

Gamete production patterns,ploidy, and population genetics reveal evolutionary significant units in hybrid water frogs (Pelophylax esculentus)

The European water frog Pelophylax esculentus is a natural hybrid between P. lessonae (genotype LL) and P. ridibundus (RR). It reproduces through hybridogenesis, eliminating one parental genome from its germline and producing gametes containing the genome of the other parental species. According to previous studies, this elimination and transmission pattern is very diverse. In mixed populations, where only diploid hybrids (LR) live in sympatry and mate with one or both parental species, the excluded genome varies among regions, and the remaining genome is transmitted clonally to haploid gametes. In all‐hybrid populations consisting of diploid (LR) and triploid (LLR and/or LRR) frogs, diploid individuals also produce gametes clonally (1n in males, 2n in females), whereas triploids eliminate the genome they have in single copy and produce haploid gametes containing the recombined other genome. However, here, too, regional differences seem to exist, and some triploids have been reported to produce diploid gametes. In order to systematically study such regional and genotype differences in gamete production, their potential origin, and their consequences for the breeding system, we sampled frogs from five populations in three European countries, performed crossing experiments, and investigated the genetic variation through microsatellite analysis. For four populations, one in Poland, two in Germany, and one in Slovakia, our results confirmed the elimination and transmission pattern described above. In one Slovakian population, however, we found a totally different pattern. Here, triploid males (LLR) produce sperm with a clonally transmitted diploid LL genome, rather than a haploid recombined L genome, and LR females clonally produce haploid R eggs, rather than diploid LR eggs. These differences among the populations in gamete production go along with differences in genomotype composition, breeding system (i.e., the way triploids are produced), and genetic variation. These differences are strong evidence for a polyphyletic origin of triploids. Moreover, our findings shed light on the evolutionary potential inherent to the P. esculentus complex, where rare events due to untypical gametogenetic processes can lead to the raise, the perpetuation, and the dispersion of new evolutionary significant lineages which may also deserve special conservation measures.     

Host plant relations in the planthopper genus Ribautodelphax (Homoptera, Delphacidae)

ABSTRACT. 1. Host plant relations of closely related species and pseudogamous triploid forms of the planthopper genus Ribautodelphax were studied.
2. From field data and experimental results it is concluded that eleven European Ribautodelphax species and undescribed taxa are monophagous or oligophagous on different grass species. Only two Ribautodelphax species are found on the same grass species in the field.
3. Differential host plant relations indicate that four recently discovered taxa are probably true species.
4. Ribautodelphax species show a more restricted host plant range in choice experiments compared with breeding tests.
5. Choice experiments indicate no differences in host plant preference between males and females of two Ribautodelphax species.
6. No differences are found in host plant relations between bisexual species and associated pseudogamous triploid forms.     

Morphometric and DNA investigations into European water frogs (Rana kl. esculenta Synklepton (Anura, Ranidae)) from different population systems

The population specific variability of diploid and triploid R. kl. esculenta individuals was investigated by means of morphometric methods (canonical discriminant analysis, UPGMA cluster analysis) and DNA fingerprinting. As a result of the morphometric investigations, as well as of the DNA investigations, a clear separation of single populations was possible. However, no correlations between the morphometry and different population systems could be recognized. Clear morphometric differences could be seen between diploid ♀♀ and ♂♂ and triploid ♀♀ on the one hand, and triploid ♂♂ on the other. While the diploid ♀♀ and ♂♂ and the triploid ♀♀ were located in the intermediate area between the parental species R. lessonae and R. ridibunda according to their morphometric parameters, the triploid ♂♂ showed a great overlap with R. lessonae. Up to now, this phenomenon has not been explained. The first results of the DNA investigations provided further hints at the high inter-individual and population-specific variability of R. kl. esculenta. R. kl. esculenta individuals of the R. lessonae/esculenta population Toter See could be distinguished from conspecific individuals of the R. ridibunda/esculenta-♀♀ population Alte Oder according to their fingerprint patterns. Moreover, in the R. lessonae / esculenta population, the fingerprints or the diploid R. kl. esculenta-♀♀ and the investigated R. lessonae-♀ were very similar. Furthermore, in this population, many R. kl. esculenta genotypes resemble R. lessonae in their morphometric features. This finding suggests the occurrence of recombination in R. kl. esculenta. In general, every population seems to have its own genetic background. A classification of water-frog populations according to population systems is only possible under certain conditions.     

Allozyme variation among natural populations of Holopedium gibberum (Crustacea; Cladocera)

• 1 Holopedium gibberum, from twenty lakes in Rhode Island and Maine, were examined for allozyme variation at five loci to determine the pattern and degree of generic variation among sites and the genetic structure within individual lakes.
• 2 There were significant differences in allele frequencies among sites. Most populations were fixed for a particular allele at each locus. Only five lakes had polymorphic populations.
• 3 Polymorphic populations showed significant deviation from expected Hardy-Weinberg genotype frequencies. In each case, there was an excess of homozygotes.
• 4 Two lakes were examined for intra-lake allele frequency differences. In one lake there were no differences. The other lake exhibited significant allele frequency differences between stations at the north and south ends of the lake.
• 5 Populations were examined for the frequency distribution of composite genotypes over three loci. Most populations were dominated by one or two genotypes.
• 6 The results suggest sporadic sexual recruitment and a high degree of genetic isolation among these populations of H. gibberum. In these respects they resemble the permanent pond populations of Daphnia magna examined by Hebert (1974a).

     

Disruption of normal meiosis in artificial inter-populational hybrid females of <Emphasis Type="Italic">Misgurnus</Emphasis> loach

Artificial cross between two genetically different populations of Japanese Misgurnus loach was made to examine the reproductive capacity of the artificial inter-populational hybrid females. Ploidy status and microsatellite genotypes of the eggs laid by these hybrids were inferred from those determined in progenies developed by normal fertilization with haploid loach sperm, induced gynogenesis with UV-irradiated goldfish sperm and/or hybridization with intact goldfish sperm. Some hybrid females laid unreduced diploid eggs genetically identical to the mother. However, these diploid eggs could not develop by spontaneous gynogenesis, but grow to triploid by incorporation of a sperm nucleus. Other hybrid females laid haploid eggs together with diploid eggs and/or various aneuploid and polyploid eggs. Thus, a disruption of normal meiosis occurred in inter-populational hybrid females. The results suggested that the two populations should be so distant as to give rise to atypical formation of unreduced and other unusual eggs in their hybrids.     

Geographical separation of diploid and triploid cytotypes of <Emphasis Type="Italic">Allium scorodoprasum</Emphasis> in Lithuania

The aim of this study was to determine the geographical and ecological distribution of Allium scorodoprasum cytotypes in Lithuania. 46 populations were studied: environmental variables were recorded and somatic chromosome numbers of 797 individuals from all populations were assessed. Diploids were found in 13 populations in the northern part of the study area, while triploids occurred in 33 populations from the western part of Lithuania. A. scorodoprasum frequently occurred in river valleys, particularly in the rarely flooded high level floodplains or on lower terraces. Only one population was recorded in Alno-Ulmion forest and three on the Glechometalia hederaceae forest edges, while 42 populations occurred in mesophilous or semidry Arrhenatheretalia elatioris, Mesobromion erecti and Trifolio-Geranietea sanguinei grasslands. No distinct differences in relative frequencies of diploid and triploid cytotypes in different plant communities were found whereas the soil chemical composition between the habitats of both cytotypes differed statistically. These differences however were indicative of the geographical separation of habitats rather than ecological differentiation between the two cytotypes. The results suggest that there were at least two separate roads of colonization of diploid and triploid A. scorodoprasum into Lithuania.