Similar Karyotypes Research Articles

Synaptic behavior of Leptodactylus pentadactylus (Anura: Leptodactylidae) by immunolocalization of proteins

Most species of the genus Leptodactylus share similar karyotypes, with 2n=22 and NF=44. The species L. pentadactylus presents a multivalent in its karyotype, resulting from multiple translocations, forming a ring chromosome during meiosis I. In this study analyzed the meiotic behavior of L. pentadactylus, from Brazilian Amazonia, through immunoprotein markers. Testicular tissues of an adult male were collected and analyzed by immunofluorescence microscopy, using antibodies to detect the following meiotic proteins: SMC3, component of chromosomal axis, and responsible for cohesion between sister chromatids; ?-H2AX in a protein marker of meiotic silencing of unsynapsed chromatin (MSUC). The results showed that: in leptotene, SMC3 and ?-H2AX mark fuzzy segments throughout all the chromatin; in the zygotene; regions that start synapses are intensely marked by ?-H2AX; in turn, with the advancement of the synapse at the end of the zygotene, ?-H2AX markings expand evenly in the chromatin; in pachytene, the synapsis remains incomplete, and several asynaptic regions were noted, with ?-H2AX markings more intense on synapsed regions of chromosomes involved or not in multivalent links; in diplotene, the synaptonemal complex is disorganized, SMC3 cohesin is present on partially decondensed, chromatin, and ?-H2AX markings are present only in some regions; in diakinesis, SMC3 maintains the same pattern of diplotene, however, ?-H2AX markings are quite reduced. The results of meiotic behavior of L. pentadactylus show asynaptic axes in pachytene, which probably do not present homology with each other, corresponding to segments that suffered multiple rearrangements. SMC3 pattern and reduction of ?-H2AX markings in diplotene, suggest decondensation of chromatin, with reactivation of transcription in chromosomal handles. The absence of ?-H2AX markings in diakinesis show that the rearranged chromosomes of L. pentadactylus do not compromise the spermatogenesis of the animal, ensuring its meiotic dynamic and fertility.

Comparative Oligo-FISH Mapping: An Efficient and Powerful Methodology To Reveal Karyotypic and Chromosomal Evolution.

Developing the karyotype of a eukaryotic species relies on identification of individual chromosomes, which has been a major challenge for most nonmodel plant and animal species. We developed a novel chromosome identification system by selecting and labeling oligonucleotides (oligos) located in specific regions on every chromosome. We selected a set of 54,672 oligos (45 nt) based on single copy DNA sequences in the potato genome. These oligos generated 26 distinct FISH signals that can be used as a "bar code" or "banding pattern" to uniquely label each of the 12 chromosomes from both diploid and polyploid (4× and 6×) potato species. Remarkably, the same bar code can be used to identify the 12 homeologous chromosomes among distantly related Solanum species, including tomato and eggplant. Accurate karyotypes based on individually identified chromosomes were established in six Solanum species that have diverged for >15 MY. These six species have maintained a similar karyotype; however, modifications to the FISH signal bar code led to the discovery of two reciprocal chromosomal translocations in Solanum etuberosum and S. caripense We also validated these translocations by oligo-based chromosome painting. We demonstrate that the oligo-based FISH techniques are powerful new tools for chromosome identification and karyotyping research, especially for nonmodel plant species.

Cytotaxonomy of Allium (Amaryllidaceae) subgenera Cyathophora and Amerallium sect. Bromatorrhiza

In the present study, we examined the karyotype data of subg. Cyathophora and sect. Bromatorrhiza, to determine some disputed karyotypes (e.g., A. spicatum and A. fasciculatum), and further to estimate the karyotype evolution along their phylogenetic frameworks. Our results revealed a fairly stable basic chromosome number (x = 8) in subg. Cyathophora, and we therefore revised x = 8 as the basic chromosome number of A. spicatum, rather than x = 10 mostly due to misidentifications concerning A. fasciculatum. The karyotype asymmetry analyses for subg. Cyathophora indicated that, the karyotype evolution for diploid species showing a high karyotype similarity was mainly due to intrachromosomal changes, while the interchromosomal changes were linked to the evolution of tetraploid populations. However, indeed different dysploid basic chromosome numbers (x = 7, 10, 11) and greatly different karyotype patterns occurred in sect. Bromatorrhiza, corresponding to the subsections revealed by molecular evidence. The combined evidence suggested that species with x = 11 compose a segmental allotriploid complex. It was also indicated that karyotype pattern of polyploids usually is closely related with their diploid progenitors.

Chromosome mapping of 28S ribosomal genes in 11 species of Cassidinae (Coleoptera: Chrysomelidae)

In this study, we examined for the first time the distribution of the 28S ribosomal genes in beetles of the subfamily Cassidinae. More than 55% of the species in this subfamily have a similar karyotype, 2n = 16 + Xyp. For this work, we selected species belonging to the tribes Cassidini and Mesomphaliini, which have, respectively, the most conserved and diversified karyotype characteristics within the Cassidinae. An analysis of 11 species revealed that rDNA sites on one pair of autosomes is the most frequent pattern, occurring in 10 species. This condition occurs in the seven genera examined and in species of both of the tribes, Cassidini and Mesomphaliini. Nevertheless, the differences in the locations of 28S rDNA were more pronounced in the tribe Cassidini and among species with similar karyotype characteristics. On the other hand, in Mesomphaliini, the increase in the diploid number was not accompanied by an increase in the number of ribosomal sites. Moreover, the comparison of the number and localization of major rDNA sites with the distribution of constitutive heterochromatin indicates that there is no direct correlation between the dispersion of constitutive heterochromatin and 28S rDNA genes in Cassidinae.

Voles of the Genus Alexandromys from the Verkhnebureinskaya Depression

Voles of an unclear taxonomic status have been found in the Bureya River depression (Khabarovsk krai) for the first time. An analysis of the nucleotide sequence of the control region in two individuals revealed their greatest similarity with species of the “maximowiczii” group. The minimum p-distance (0.0217 ± 0.0044) was observed between individuals from the Bureya River depression and Alexandromys evoronensis studied earlier. The karyotype of one individual studied had a chromosomal aberration distinguished at the heterozygous state (2n = 37; NF = 55). A similar karyotype was described in the polymorphic A. maximowiczii population from the Khentii Mountains in Mongolia.

Heterochromatic and cytomolecular diversification in the Caesalpinia group (Leguminosae): Relationships between phylogenetic and cytogeographical data

The pantropical Caesalpinia group comprises 27 genera and approximately 205 species. The Neotropical species of the group are distributed in three main centers of diversity: the Andes, Mesoamerica (including Mexico, Central America, the southern USA and the Caribbean), and Northeastern Brazil. Our study investigates patterns of phylogenetic, environmental and geographical variation in an attempt to explain the karyotypic diversity which occurs within the Caesalpinia group. Cytogenetic analyses were based on chromosome number and morphology, CMA and DAPI heterochromatic bands, distribution of rDNA sites, and their molecular phylogenetic relationships based on the plastid markers matK, rps16, trnDT, trnL and ycf6 and the nuclear ribosomal marker ITS. Ecological differentiation among cytotypes was tested by comparing sets of climatic variables. In total, twenty species from ten genera of the Caesalpinia group were analysed, and all of them were found to have the same chromosome number (2n=24). CMA+/DAPI− bands were observed on the short arms of the acrocentric chromosomes in all of the species. Additionally, three different patterns were observed on the metacentric chromosomes: proximal CMA+/DAPI− bands, proximal CMA0/DAPI− bands and terminal CMA+/DAPI− bands. The 45S rDNA sites varied from eight to 14, always co-localizing with CMA+/DAPI− bands of acrocentrics, while 5S rDNA was localized in only a single chromosome pair in most species. A correlation between heterochromatic patterns and the geographic distributions/ecological niche of species was observed. Our analyses support some shared effects of the environment, when integrated with phylogeny and geography, on the CMA/DAPI variability. Thus, CMA+ heterochromatin is highly dynamic and its amplification/deamplification might be non-random, generating similar karyotypes in species which are not sister taxa in the molecular phylogeny but which co-occur in similar environments.

Evolutionary Relationships and Cytotaxonomy Considerations in the Genus Pyrrhulina (Characiformes, Lebiasinidae).

Although fishes exhibit the greatest biodiversity among the vertebrates, a large percentage of this fauna is still underexplored on evolutionary cytogenetic questions, particularly the miniature species. The Lebiasinidae family is a particular example for such case. This study is the first one presenting differential cytogenetic methods, such as C-banding, repetitive DNAs mapping, comparative genomic hybridization (CGH), and whole chromosome painting in lebiasinid species. Pyrrhulina australis and Pyrrhulina aff. australis were deeply investigated concerning their chromosomal patterns and evolutionary relationships. These species have a very similar morphology, but they can be distinguished by a longitudinal midlateral faintly dark stripe exclusive for Pyrrhulina aff. australis. Both species presented 2n = 40 chromosomes (4st +36a), without heteromorphic sex chromosomes. However, despite their morphological and karyotype resemblance, it was evidenced that both species have already gone through a significant genomic divergence, thus corresponding to distinct evolutionary units. Furthermore, to give additional support to some proposals on evolutionary relationship among Lebiasinidae with other fish families, a chromosomal comparative approach with Erythrinus erythrinus, a representative species of the Erythrinidae family, was also performed. In addition to have similar karyotype structure, mainly composed by acrocentric chromosomes, both species share uncommon genomic similarities, such as (i) syntenic location of 5S and 18S rDNA sequences; (ii) huge dispersion of multiple 5S rDNA sites in the karyotypes; and (iii) complex association between 5S rDNA and Rex3 elements. CGH experiments, despite reinforcing some shared genomic homologies, also highlighted that both Pyrrhulina and Erythrinus have a range of nonoverlapping species-specific signals. The overall chromosomal data proved to be effective markers for the cytotaxonomy and evolutionary process among Lebiasinidae fishes.

Density-dependent processes determine the distribution of chromosomal races of the common shrew Sorex araneus (Lipotyphla, Mammalia)

The common shrew is subdivided into 74 chromosomal races, widely distributed in the postglacial area from the Britain Islands to Lake Baikal. Based on 1969 karyotypes from 216 localities, we present for the first time a map of ranges of 25 chromosomal races (except the Altai race) currently known in Russia. We revealed two centers of high karyotypic diversity: the western (near Baltic Sea) and the eastern (near Baikal Lake). The studied races were categorized as small-, medium-, and large-range races, and small-range races concentrated around those two centers of karyotypic diversity. We did not find any significant association between race range size and ecological zone, latitude, or the ambient temperature. Physical barriers, such as Ural Mountain or rivers, do not limit race distribution. The width of rivers that divide a range of a single race or ranges of two different races does not differ. We supposed that the occupation of an area by a race could limit the invasion of a different race from an adjacent area and expansion of its range, thus contributing to race parapatric distribution alone without additional effects of physical barriers. Based on karyotype similarity and geographic localization, we combined races into four “karyotypic chains,” in which the races can be derived from one another consequently by a single chromosomal translocation. The present distribution of the common shrew races in Russia supports the idea that it has resulted from recolonization from refugia governed by the density-dependent processes.

Analisis Karyotipe Bawang Merah Hasil Persarian Bebas

Three varieties of seed origin shallot, namely Biru, Tiron and Tutuk were grown to be taken their roots for chromosom observation. The ratio of Chromosom arm obtained would be used for: (1) determine chromosome shape based on centromere position, (2) the homologous chromosome pair, (3) karyoptype composition. The result revealed showed that the chromosome number of the three varieties of shallot were 16 with the formula of chromosome is 2n = 2x = 16. The ration of arm length of the three varieties formed the same chromosome formula: 4M (metacentric) + 3SM (submetacentric) + 1ST (subtelocentric). This results revealed that the open pollinated shallot would form the similar karyotype with the parents.

Chromosomal similarity between two species ofApteronotus albifronscomplex (Apteronotidae–Gymnotiformes) implications in cytotaxonomy and karyotypic evolution

AbstractApteronotidae is one of the oldest families from the order Gymnotiformes, and is composed of 94 species that can be found from Panama to northern Argentina. Some groups such as Apteronotus present taxonomic problems, mainly related to interspecific morphological similarity. In the present study, two species belonging to Apteronotus albifrons complex from different hydrographic basins were cytogenetically analyzed in order to define chromosomal structure and propose evolutionary trends for the group. Apteronotus albifrons presented 2n = 24 (14 m + 2sm + 8a) FN = 40 and Apteronotus caudimaculosus 2n = 24 (12 m + 2sm + 10a) FN = 38; this difference in karyotypic formulae can be explained by pericentric inversion involving metacentric and acrocentric chromosomes. The karyotypic similarity between these two species indicates a chromosomal diversification, characterized by changes in karyotype formulae, which were considered an excellent cytotaxonomic marker to discriminate A. caudimaculosus of other po...

Chromosomal evolution in large pelagic oceanic apex predators, the barracudas (Sphyraenidae, Percomorpha).

Sphyraena (barracudas) represents the only genus of the Sphyraenidae family and includes 27 species distributed into the tropical and subtropical oceanic regions. These pelagic predators can reach large sizes and, thus, attracting significant interest from commercial and sport fishing. Evolutionary data for this fish group, as well its chromosomal patterns, are very incipient. In the present study, the species Sphyraena guachancho, S. barracuda, and S. picudilla were analyzed under conventional (Giemsa staining, C-banding, and Ag-NOR) and molecular (CMA3 banding, and in situ hybridization with 18S rDNA, 5S rDNA, and telomeric probes) cytogenetic methods. The karyotypic patterns contrast with the current phylogenetic relationships proposed for this group, showing by themselves to be distinct among closely related species, and similar among less related ones. This indicates homoplasic characteristics, with similar karyotype patterns originating at least twice, independently. Although still cytogenetically poor investigated, our data were enough to put in evidence a variety of ancient conserved traits and evolutionary novelties for the Sphyraena genus. In this sense, it is fundamental that a larger number of Sphyraenidae species, as well as of other phylogenetically related families, be also investigated. This will solidify the knowledge of their karyotypic patterns, and the evolutionary path followed by the species of this particular fish family.

Karyotype analysis of three species of Corydoras (Siluriformes: Callichthyidae) from southern Brazil: rearranged karyotypes and cytotaxonomy

ABSTRACT The genus Corydoras comprises a diversity of species with different diploid numbers. We compared cytogenetic data among Corydoras species from different rivers of the Ponta Grossa Arch region in southern Brazil. Corydoras ehrhardti and C. aff. paleatus have a similar karyotype formula and the same diploid number (2n = 44). Corydoras lacrimostigmata has a higher diploid number, with 2n = 58 chromosomes. Fluorescence in situ hybridization using 5S and 18S ribosomal DNA probes suggests that these ribosomal DNA sequences are involved in chromosomal rearrangements in these Corydoras species. 5S rDNA is a chromosomal marker that is considered to be unique to the species analyzed in this study. Signals of interstitial telomeric sites are seen in a chromosome pair of C. lacrimostigmata, suggesting chromosomal rearrangements via fusions or translocations. This study revealed that C. ehrhardti and C. aff. paleatus have exclusive chromosomal markers associated with chromosome differentiation, which we speculate to prevent genetic introgression.

Comparative cytogenetics of tree frogs of the Dendropsophus marmoratus (Laurenti, 1768) group: conserved karyotypes and interstitial telomeric sequences.

The diploid number 2n = 30 is a presumed synapomorphy of Dendropsophus Fitzinger, 1843, although a noticeable variation in the number of biarmed/telocentric chromosomes is observed in this genus. Such a variation suggests that several chromosomal rearrangements took place after the evolutionary origin of the hypothetical ancestral 30-chromosome karyotype; however, the inferred rearrangements remain unknown. Distinct numbers of telocentric chromosomes are found in the two most cytogenetically studied species groups of Dendropsophus. In contrast, all three species of the Dendropsophus marmoratus (Laurenti, 1768) group that are already karyotyped presented five pairs of telocentric chromosomes. In this study, we analyzed cytogenetically three additional species of this group to investigate if the number of telocentric chromosomes in this group is not as variable as in other Dendropsophus groups. We described the karyotypes of Dendropsophus seniculus (Cope, 1868), Dendropsophus soaresi (Caramaschi & Jim, 1983) and Dendropsophus novaisi (Bokermann, 1968) based on Giemsa staining, C-banding, silver impregnation and in situ hybridization with telomeric probes. Dendropsophus seniculus, Dendropsophus soaresi and Dendropsophus novaisi presented five pairs of telocentric chromosomes, as did the remaining species of the group previously karyotyped. Though the species of this group show a high degree of karyotypic similarity, Dendropsophus soaresi was unique in presenting large blocks of het-ITSs (heterochromatic internal telomeric sequences) in the majority of the centromeres. Although the ITSs have been interpreted as evidence of ancestral chromosomal fusions and inversions, the het-ITSs detected in the karyotype of Dendropsophus soaresi could not be explained as direct remnants of ancestral chromosomal rearrangements because no evidence of chromosomal changes emerged from the comparison of the karyotypes of all of the species of the Dendropsophus marmoratus group.

Classical and Molecular Cytogenetics of the Panther Genet Genetta maculata (Mammalia, Carnivora, Viverridae)

Genets (Genetta) are a genus of African mammalian carnivorans with 14 currently recognized species, although taxonomic uncertainties remain, particularly regarding the number of species within the large-spotted genet complex. This study presents the first banded karyotype and molecular cytogenetic analysis of a genetically identified panther genet, Genetta maculata, the most common and widespread taxon of the large-spotted genet complex, with a wide distribution in sub-Saharan Africa. Sampled in Gauteng Province, South Africa, it could be assigned to the subspecies G. m. letabae on geographic grounds and had a similar karyotype (2n = 52, FNa = 96) to those published for a panther genet from Ethiopia and for the West African large-spotted genet G. pardina. Notably, the specimen had a different autosomal morphology (2 acrocentric chromosomes) from that previously attributed to letabae (a single acrocentric chromosome), but the latter assignment was uncertain because the studied individuals were captive born and assigned based solely on a presumed origin in the former Transvaal Province of South Africa. Fluorescence in situ hybridization with a telomere repeat probe revealed the presence of telomeric sequences in the centromeres of most chromosomes, the so-called interstitial telomeric sites (ITSs). Since genets seem to have a unique, highly rearranged karyotype among feliforms and relatively low interspecific karyotypic variation, and considering the known instability of ITSs, we suggest that the large amount of ITSs found here might be due to evolutionarily recent extensive genomic rearrangements. This study provides cytogenetic information that contributes to our understanding of chromosomal variation and genomic rearrangements in genets, and valuable baseline data for future studies of karyotype evolution in carnivores in general and viverrids in particular.

First detailed karyo-morphological analysis and molecular cytological study of leafy cardoon and globe artichoke, two multi-use Asteraceae crops.

Traditionally globe artichoke and leafy cardoon have been cultivated for use as vegetables but these crops are now finding multiple new roles in applications ranging from paper production to cheese preparation and biofuel use, with interest in their functional food potential. So far, their chromosome complements have been poorly investigated and a well-defined karyotype was not available. In this paper, a detailed karyo-morphological analysis and molecular cytogenetic studies were conducted on globe artichoke (Cynara cardunculus Linnaeus, 1753 var. scolymus Fiori, 1904) and leafy cardoon (Cynara cardunculus Linneaus, 1753 var. altilis De Candolle, 1838). Fluorescent In Situ Hybridization In Suspension (FISHIS) was applied to nuclei suspensions as a fast method for screening of labelling probes, before metaphase spread hybridization. Classic Fluorescent In Situ Hybridization (FISH) on slide, using repetitive telomeric and ribosomal sequences and Simple Sequence Repeats (SSRs) oligonucleotide as probes, identified homologous chromosome relationships and allowed development of molecular karyotypes for both varieties. The close phylogenetic relationship between globe artichoke and cardoon was supported by the very similar karyotypes but clear chromosomal structural variation was detected. In the light of the recent release of the globe artichoke genome sequencing, these results are relevant for future anchoring of the pseudomolecule sequence assemblies to specific chromosomes. In addition, the DNA content of the two crops has been determined by flow cytometry and a fast method for standard FISH on slide and methodological improvements for nuclei isolation are described.

Chromosome mapping of repetitive DNAs in sergeant major fishes (Abudefdufinae, Pomacentridae): a general view on the chromosomal conservatism of the genus

Species of the Abudefduf genus (sergeant-majors) are widely distributed in the Indian, Pacific and Atlantic oceans, with large schools inhabiting rocky coastal regions and coral reefs. This genus consists of twenty recognized species are of generalist habit, showing typical characteristics of colonizers. Some populations maintain gene flow between large oceanic areas, a condition that may influence their cytogenetic features. A number of species have been shown to be invaders and able to hybridize with local species. However, cytogenetic data in this genus are restricted to few species. In this way, the present study includes the chromosomal investigation, using conventional (Giemsa staining, Ag-NOR and C-banding) and molecular (in situ mapping of six different repetitive DNA classes) approaches in four Abudefduf species from different oceanic regions (A. bengalensis and A. sexfasciatus from the Indo-Pacific, A. vaigiensis from the Indian and A. saxatilis from the Atlantic oceans, respectively), to investigate the evolutionary events associated with the chromosomal diversification in this group. All species share a similar karyotype (2n=48; NF=52), except A. sexfasciatus (2n=48; NF=50), which possesses a characteristic pericentric inversion in the NOR-bearing chromosomal pair. Mapping of repetitive sequences suggests a chromosomal conservatism in this genus. The high karyotypic similarity between allopatric species of Abudefduf may be related to the success of natural viable hybrids among species with recent secondary contact.

Chromosomal analysis of Physalaemus kroyeri and Physalaemus cicada (Anura, Leptodactylidae).

All the species of Physalaemus Fitzinger, 1826 karyotyped up until now have been classified as 2n = 22. The species of the Physalaemus cuvieri group analyzed by C-banding present a block of heterochromatin in the interstitial region of the short arm of pair 5. Physalaemus cicada Bokermann, 1966 has been considered to be a member of the Physalaemus cuvieri species group, although its interspecific phylogenetic relationships remain unknown. The PcP190 satellite DNA has been mapped on the chromosomes of most of the species of the Physalaemus cuvieri group. For two species, Physalaemus cicada and Physalaemus kroyeri (Reinhardt & Lütken, 1862), however, only the chromosome number and morphology are known. Given this, the objective of the present study was to analyze the chromosomes of Physalaemus cicada and Physalaemus kroyeri, primarily by C-banding and PcP190 mapping. The results indicate that Physalaemus kroyeri and Physalaemus cicada have similar karyotypes, which were typical of Physalaemus. In both species, the NORs are located on the long arm of pair 8, and the C-banding indicated that, among other features, Physalaemus kroyeri has the interstitial band on chromosome 5, which is however absent in Physalaemus cicada. Even so, a number of telomeric bands were observed in Physalaemus cicada. The mapping of the PcP190 satellite DNA highlighted areas of the centromeric region of the chromosomes of pair 1 in both species, although in Physalaemus kroyeri, heteromorphism was also observed in pair 3. The cytogenetic evidence does not support the inclusion of Physalaemus cicada in the Physalaemus cuvieri group. In the case of Physalaemus kroyeri, the interstitial band on pair 5 is consistent with the existence of a cytogenetic synapomorphy in the Physalaemus cuvieri species group.

Karyotypic stability in the paleopolyploid genus Ceiba Mill. (Bombacoideae, Malvaceae)

The genus Ceiba Mill. belongs to the subfamily Bombacoideae (Malvaceae), a paleopolyploid lineage characterized by numerous small chromosomes, which has frequently been reported to have variable intra- and interspecific chromosome numbers. The genus is of Miocene origin, representing a suitable model for studying the relationships between chromosome variability and paleopolyploidy. A comparative cytogenetic analysis of five Ceiba species was undertaken to determine their karyotype variability. New chromosome number counts, chromosome morphological observations, CMA/DAPI double staining, and in situ hybridization (FISH) with 5S and 45S rDNA were performed for five Ceiba species, which represent three out of five main lineages of the genus. Karyotypic data were discussed in the light of molecular phylogenies available for the group. All species showed 2n = 86 and similar karyotypes, composed predominantly of metacentric chromosomes. Two pairs of CMA+/DAPI− bands were located on the short arms of the metacentric chromosomes. The CMA+ bands colocated with 45S rDNA sites, while the 5S rDNA sites were situated in the interstitial regions of other chromosome pairs. Contrary to the intra- and interspecific chromosome number diversity reported for Ceiba species in the literature, our findings suggest chromosome number stability in four of the five lineages within the genus for which data are available. Moreover, our data suggest that karyotypes are evolutionary conserved in the three lineages for which we generated new karyotypic data. Our data, as well as recent cytogenetic reviews of other Bombacoideae genera, indicate numerical stability for these taxa suggesting that counting errors, especially in earlier research, may have overestimated karyotype variability. Chromosome count errors can be attributed to technical difficulties associated with high chromosome numbers, and/or the reduced size of Bombacoideae chromosomes.

Chromosome numbers and karyomorphology of Festuca circummediterranea Patzke group (Poaceae, Loliinae)

The first comprehensive karyological overview of the group of Festuca circummediterranea, comprising 10 Euro-Mediterranean taxa (5 species and 7 subspecies, including autonyms), is provided. Thirty populations were sampled from across almost the whole distributional range of the aggregate, including the loci classici of each taxon. The first chromosome counts for F. jeanpertii subsp. jeanpertii, subsp. achaica, and subsp. gracilis are reported. All the taxa were found to be diploid (2n = 14) and have a similar karyotype, characterized by the predominace of metacentric and submetacentric chromosomes; the occurrence of B-chromosomes was recorded from a single taxon, F. marginata subsp. gallica.

Divergent evolutionary behavior of H3 histone gene and rDNA clusters in venerid clams.

BackgroundHistone H3 gene clusters have been described as highly conserved chromosomal markers in invertebrates. Surprisingly, in bivalves remarkable interspecific differences were found among the eight mussels and between the two clams in which histone H3 gene clusters have already been located. Although the family Veneridae comprises 10 % of the species of marine bivalves, their chromosomes are poorly studied. The clams belonging to this family present 2n = 38 chromosomes and similar karyotypes showing chromosome pairs gradually decreasing in length. In order to assess the evolutionary behavior of histone and rRNA multigene families in bivalves, we mapped histone H3 and ribosomal RNA probes to chromosomes of ten species of venerid clams.ResultsIn contrast with the reported conservation of histone H3 gene clusters and their intercalary location in invertebrates, these loci varied in number and were mostly subterminal in venerid clams. On the other hand, while a single 45S rDNA cluster, highly variable in location, was found in these organisms, 5S rDNA clusters showed interspecific differences in both number and location. The distribution patterns of these sequences were species-specific and mapped to different chromosomal positions in all clams but Ruditapes decussatus, in which one of the minor rDNA clusters and the major rDNA cluster co-located.ConclusionThe diversity in the distribution patterns of histone H3 gene, 5S rDNA and 28S rDNA clusters found in venerid clams, together with their different evolutionary behaviors in other invertebrate taxa, strongly suggest that the control of the spreading of these multigene families in a group of organisms relies upon a combination of evolutionary forces that operate differently depending not only on the specific multigene family but also on the particular taxa. Our data also showed that H3 histone gene and rDNA clusters are useful landmarks to integrate nex-generation sequencing (NGS) and evolutionary genomic data in non-model species.