Evolution of bird sex chromosomes: a cytogenomic approach in Palaeognathae species.

BACKGROUND: Different patterns of sex chromosome differentiation are seen in Palaeognathae birds, a lineage that includes the ratites (Struthioniformes, Rheiformes, Apterygiformes, Casuariiformes, and the sister group Tinamiformes). While some Tinamiform species have well-differentiated W chromosomes, both Z and W of all the flightless ratites are still morphologically undifferentiated. Here, we conducted a comprehensive analysis of the ZW differentiation in birds using a combination of cytogenetic, genomic, and bioinformatic approaches. The whole set of satDNAs from the emu (Dromaius novaehollandiae) was described and characterized. Furthermore, we examined the in situ locations of these satDNAs alongside several microsatellite repeats and carried out Comparative Genomic Hybridizations in two related species: the greater rhea (Rhea americana) and the tataupa tinamou (Crypturellus tataupa). RESULTS: From the 24 satDNA families identified (which represent the greatest diversity of satDNAs ever uncovered in any bird species), only three of them were found to accumulate on the emu's sex chromosomes, with no discernible accumulation observed on the W chromosome. The W chromosomes of both the greater rhea and the emu did not exhibit a significant buildup of either C-positive heterochromatin or repetitive DNAs, indicating their large undifferentiation both at morphological and molecular levels. In contrast, the tataupa tinamou has a highly differentiated W chromosome that accumulates several DNA repeats. CONCLUSION: The findings provide new information on the architecture of the avian genome and an inside look at the starting points of sex chromosome differentiation in birds.

Comparative cytogenetics in Tyrannidae (Aves, Passeriformes): High genetic diversity despite conserved karyotype organization.

Introduction Passeriformes has the greatest species diversity among Neoaves, and the Tyrannidae is the richest in this order with about 600 valid species. The diploid number of this family remains constant, ranging from 2n = 76 to 84, but the chromosomal morphology varies, indicating the occurrence of different chromosomal rearrangements. Cytogenetic studies of the Tyrannidae remain limited, with approximately 20 species having been karyotyped thus far. This study aimed to describe the karyotypes of two species from this family, Myiopagis viridicata and Sirystes sibilator. Methods Skin biopsies were taken from each individual to establish fibroblast cell cultures and to obtain chromosomal preparations using the standard methodology. The chromosomal distribution of constitutive heterochromatin was investigated by C-banding, while the location of simple repetitive sequences (SSRs), 18S rDNA, and telomeric sequences were found through fluorescence in situ hybridization. Results The karyotypes of both species are composed of 2n = 80. The 18S rDNA probes hybridized into two pairs of microchromosomes in M. viridicata, but only a single pair in S. sibilator. Only the telomeric portions of each chromosome in both species were hybridized by the telomere sequence probes. Most of the SSRs were found accumulated in the centromeric and telomeric regions of several macro- and microchromosomes in both species, which likely correspond to the heterochromatin-rich regions. Conclusion Although both species analyzed showed a conserved karyotype organization (2n = 80), our study revealed significant differences in their chromosomal architecture, rDNA distribution, and SSR accumulation. These findings were discussed in the context of the evolution of Tyrannidae karyotypes.

Satellite DNAs, heterochromatin, and sex chromosomes of the wattled jacana (Charadriiformes; Jacanidae): a species with highly rearranged karyotype.

Charadriiformes, which comprises shorebirds and their relatives, is one of the most diverse avian orders, with over 390 species showing a wide range of karyotypes. Here, we isolated and characterized the whole collection of satellite DNAs (satDNAs) at both molecular and cytogenetic levels of one of its representative species, named the wattled jacana (Jacana jacana), a species that contains a typical ZZ/ZW sex chromosome system and a highly rearranged karyotype. In addition, we also investigate the in situ location of telomeric and microsatellite repeats. A small catalog of 11 satDNAs was identified that typically accumulated on microchromosomes and on the W chromosome. The latter also showed a significant accumulation of telomeric signals, being (GA)10 the only microsatellite with positive hybridization signals among all the 16 tested ones. These current findings contribute to our understanding of the genomic organization of repetitive DNAs in a bird species with high degree of chromosomal reorganization contrary to the majority of bird species that have stable karyotypes.

Satellitome Analysis in the Southern Lapwing (Vanellus chilensis) Genome: Implications for SatDNA Evolution in Charadriiform Birds.

Vanellus (Charadriidae; Charadriiformes) comprises around 20 species commonly referred to as lapwings. In this study, by integrating cytogenetic and genomic approaches, we assessed the satellite DNA (satDNA) composition of one typical species, Vanellus chilensis, with a highly conserved karyotype. We additionally underlined its role in the evolution, structure, and differentiation process of the present ZW sex chromosome system. Seven distinct satellite DNA families were identified within its genome, accumulating on the centromeres, microchromosomes, and the W chromosome. However, these identified satellite DNA families were not found in two other Charadriiformes members, namely Jacana jacana and Calidris canutus. The hybridization of microsatellite sequences revealed the presence of a few repetitive sequences in V. chilensis, with only two out of sixteen displaying positive hybridization signals. Overall, our results contribute to understanding the genomic organization and satDNA evolution in Charadriiform birds.

Understanding the chromosomal evolution in cuckoos (Aves, Cuculiformes): a journey through unusual rearrangements.

The Cuculiformes are a family of over 150 species that live in a range of habitats, such as forests, savannas, and deserts. Here, bacterial artificial chromosome (BAC) probes (75 from chicken and 14 from zebra finch macrochromosomes 1-10 +ZW and for microchromosomes 11-28 (except 16)) were used to investigate chromosome homologies between chicken and the squirrel cuckoo (Piaya cayana). In addition, repetitive DNA probes were applied to characterize the chromosome organization and to explore the role of these sequences in the karyotype evolution of P. cayana. We also applied BAC probes for chicken chromosome 17 and Z to the guira cuckoo (Guira guira) to test whether this species has an unusual Robertsonian translocation between a microchromosome and the Z chromosome, recently described in the smooth-billed ani (Crotophaga ani). Our results revealed extensive chromosome reorganization with inter- and intrachromosomal rearrangements in P. cayana, including a conspicuous chromosome size and heterochromatin polymorphism on chromosome pair 20. Furthermore, we confirmed that the Z-autosome Robertsonian translocation found in C. ani is also found in G. guira, not P. cayana. These findings suggest that this translocation occurred prior to the divergence between C. ani and G. guira, but after the divergence with P. cayana.

A Bird's-Eye View of Chromosomic Evolution in the Class Aves.

Birds (Aves) are the most speciose of terrestrial vertebrates, displaying Class-specific characteristics yet incredible external phenotypic diversity. Critical to agriculture and as model organisms, birds have adapted to many habitats. The only extant examples of dinosaurs, birds emerged ~150 mya and >10% are currently threatened with extinction. This review is a comprehensive overview of avian genome ("chromosomic") organization research based mostly on chromosome painting and BAC-based studies. We discuss traditional and contemporary tools for reliably generating chromosome-level assemblies and analyzing multiple species at a higher resolution and wider phylogenetic distance than previously possible. These results permit more detailed investigations into inter- and intrachromosomal rearrangements, providing unique insights into evolution and speciation mechanisms. The 'signature' avian karyotype likely arose ~250 mya and remained largely unchanged in most groups including extinct dinosaurs. Exceptions include Psittaciformes, Falconiformes, Caprimulgiformes, Cuculiformes, Suliformes, occasional Passeriformes, Ciconiiformes, and Pelecaniformes. The reasons for this remarkable conservation may be the greater diploid chromosome number generating variation (the driver of natural selection) through a greater possible combination of gametes and/or an increase in recombination rate. A deeper understanding of avian genomic structure permits the exploration of fundamental biological questions pertaining to the role of evolutionary breakpoint regions and homologous synteny blocks.

Comparative chromosome painting in three Pelecaniformes species (Aves): Exploring the role of macro and microchromosome fusions in karyotypic evolution.

Pelecaniformes is an order of waterbirds that exhibit diverse and distinct morphologies. Ibis, heron, pelican, hammerkop, and shoebill are included within the order. Despite their fascinating features, the phylogenetic relationships among the families within Pelecaniformes remain uncertain and pose challenges due to their complex evolutionary history. Their karyotypic evolution is another little-known aspect. Therefore, to shed light on the chromosomal rearrangements that have occurred during the evolution of Pelecaniformes, we have used whole macrochromosome probes from Gallus gallus (GGA) to show homologies on three species with different diploid numbers, namely Cochlearius cochlearius (2n = 74), Eudocimus ruber (2n = 66), and Syrigma sibilatrix (2n = 62). A fusion between GGA6 and GGA7 was found in C. cochlearius and S. sibilatrix. In S. sibilatrix the GGA8, GGA9 and GGA10 hybridized to the long arms of biarmed macrochromosomes, indicating fusions with microchromosomes. In E. ruber the GGA7 and GGA8 hybridized to the same chromosome pair. After comparing our painting results with previously published data, we show that distinct chromosomal rearrangements have occurred in different Pelecaniformes lineages. Our study provides new insight into the evolutionary history of Pelecaniformes and the chromosomal changes involving their macrochromosomes and microchromosomes that have taken place in different species within this order.

Hybridization in Canids-A Case Study of Pampas Fox (Lycalopex gymnocercus) and Domestic Dog (Canis lupus familiaris) Hybrid.

Hybridization between species with different evolutionary trajectories can be a powerful threat to wildlife conservation. Anthropogenic activities, such as agriculture and livestock, have led to the degradation and loss of natural habitats for wildlife. Consequently, the incidence of interspecific hybridization between wild and domestic species has increased, although cases involving species of different genera are rare. In Vacaria, a Southern city in Brazil, a female canid with a strange phenotype, which had characteristics between the phenotype of the domestic dog (Canis familiaris) and that of the pampas fox (Lycalopex gymnocercus), was found. Our analysis suggests that the animal is a hybrid between a domestic dog and a pampas fox, but future studies are necessary to investigate additional cases of this hybridization in nature. This finding worries for the conservation of wild canids in South America, especially concerning Lycalopex species. Hybridization with the domestic dog may have harmful effects on pampas fox populations due to the potential for introgression and disease transmission by the domestic dog. Therefore, future studies to explore the consequences of hybridization on genetics, ecology, and behavior of wild populations will be essential to improve the conservation of this species.

Following the Pathway of W Chromosome Differentiation in Triportheus (Teleostei: Characiformes).

In this work, we trace the dynamics of satellite DNAs (SatDNAs) accumulation and elimination along the pathway of W chromosome differentiation using the well-known Triportheus fish model. Triportheus stands out due to a conserved ZZ/ZW sex chromosome system present in all examined species. While the Z chromosome is conserved in all species, the W chromosome is invariably smaller and exhibits differences in size and morphology. The presumed ancestral W chromosome is comparable to that of T. auritus, and contains 19 different SatDNA families. Here, by examining five additional Triportheus species, we showed that the majority of these repetitive sequences were eliminated as speciation was taking place. The W chromosomes continued degeneration, while the Z chromosomes of some species began to accumulate some TauSatDNAs. Additional species-specific SatDNAs that made up the heterochromatic region of both Z and W chromosomes were most likely amplified in each species. Therefore, the W chromosomes of the various Triportheus species have undergone significant evolutionary changes in a short period of time (15-25 Myr) after their divergence.

Cross-species chromosome painting and repetitive DNA mapping illuminate the karyotype evolution in true crocodiles (Crocodylidae).

Crocodilians have maintained very similar karyotype structures and diploid chromosome numbers for around 100 million years, with only minor variations in collinearity. Why this karyotype structure has largely stayed unaltered for so long is unclear. In this study, we analyzed the karyotypes of six species belonging to the genera Crocodylus and Osteolaemus (Crocodylidae, true crocodiles), among which the Congolian endemic O. osborni was included and investigated. We utilized various techniques (differential staining, fluorescence in situ hybridization with repetitive DNA and rDNA probes, whole chromosome painting, and comparative genomic hybridization) to better understand how crocodile chromosomes evolved. We studied representatives of three of the four main diploid chromosome numbers found in crocodiles (2n = 30/32/38). Our data provided new information about the species studied, including the identification of four major chromosomal rearrangements that occurred during the karyotype diversification process in crocodiles. These changes led to the current diploid chromosome numbers of 2n = 30 (fusion) and 2n = 38 (fissions), derived from the ancestral state of 2n = 32. The conserved cytogenetic tendency in crocodilians, where extant species keep near-ancestral state, contrasts with the more dynamic karyotype evolution seen in other major reptile groups.

Cytogenetics Meets Genomics: Cytotaxonomy and Genomic Relationships among Color Variants of the Asian Arowana Scleropages formosus.

Scleropages formosus (Osteoglossiformes, Teleostei) represents one of the most valued ornamental fishes, yet it is critically endangered due to overexploitation and habitat destruction. This species encompasses three major color groups that naturally occur in allopatric populations, but the evolutionary and taxonomic relationships of S. formosus color varieties remain uncertain. Here, we utilized a range of molecular cytogenetic techniques to characterize the karyotypes of five S. formosus color phenotypes, which correspond to naturally occurring variants: the red ones (Super Red); the golden ones (Golden Crossback and Highback Golden); the green ones (Asian Green and Yellow Tail Silver). Additionally, we describe the satellitome of S. formosus (Highback Golden) by applying a high-throughput sequencing technology. All color phenotypes possessed the same karyotype structure 2n = 50 (8m/sm + 42st/a) and distribution of SatDNAs, but different chromosomal locations of rDNAs, which were involved in a chromosome size polymorphism. Our results show indications of population genetic structure and microstructure differences in karyotypes of the color phenotypes. However, the findings do not clearly back up the hypothesis that there are discrete lineages or evolutionary units among the color phenotypes of S. formosus, but another case of interspecific chromosome stasis cannot be excluded.

Microchromosome BAC-FISH Reveals Different Patterns of Genome Organization in Three Charadriiformes Species.

Microchromosomes, once considered unimportant elements of the genome, represent fundamental building blocks of bird karyotypes. Shorebirds (Charadriiformes) comprise a wide variety of approximately 390 species and are considered a valuable model group for biological studies. Despite this variety, cytogenetic analysis is still very scarce in this bird order. Thus, the aim of this study was to provide insight into the Charadriiformes karyotype, with emphasis on microchromosome evolution in three species of shorebirds-Calidris canutus, Jacana jacana, and Vanellus chilensis-combining classical and molecular approaches. Cross-species FISH mapping applied two BAC probes for each microchromosome, GGA10-28 (except GGA16). The experiments revealed different patterns of microchromosome organization in the species investigated. Hence, while in C. canutus, we found two microchromosomes involved in chromosome fusions, they were present as single pairs in V. chilensis. We also described a new chromosome number for C. canutus (2n = 92). Hence, this study contributed to the understanding of genome organization and evolution of three shorebird species.

Genomic Organization of Microsatellites and LINE-1-like Retrotransposons: Evolutionary Implications for Ctenomys minutus (Rodentia: Ctenomyidae) Cytotypes.

The Neotropical underground rodents of the genus Ctenomys (Rodentia: Ctenomyidae) comprise about 65 species, which harbor the most significant chromosomal variation among mammals (2n = 10 to 2n = 70). Among them, C. minutus stands out with 45 different cytotypes already identified, among which, seven parental ones, named A to G, are parapatrically distributed in the coastal plains of Southern Brazil. Looking for possible causes that led to such extensive karyotype diversification, we performed chromosomal mapping of different repetitive DNAs, including microsatellites and long interspersed element-1 (LINE-1) retrotransposons in the seven parental cytotypes. Although microsatellites were found mainly in the centromeric and telomeric regions of the chromosomes, different patterns occur for each cytotype, thus revealing specific features. Likewise, the LINE-1-like retrotransposons also showed a differential distribution for each cytotype, which may be linked to stochastic loss of LINE-1 in some populations. Here, microsatellite motifs (A)30, (C)30, (CA)15, (CAC)10, (CAG)10, (CGG)10, (GA)15, and (GAG)10 could be mapped to fusion of chromosomes 20/17, fission and inversion in the short arm of chromosome 2, fusion of chromosomes 23/19, and different combinations of centric and tandem fusions of chromosomes 22/24/16. These data provide evidence for a correlation between repetitive genomic content and localization of evolutionary breakpoints and highlight their direct impact in promoting chromosomal rearrangements.

Satellitome analysis illuminates the evolution of ZW sex chromosomes of Triportheidae fishes (Teleostei: Characiformes).

Satellites are an abundant source of repetitive DNAs that play an essential role in the chromosomal organization and are tightly linked with the evolution of sex chromosomes. Among fishes, Triportheidae stands out as the only family where almost all species have a homeologous ZZ/ZW sex chromosomes system. While the Z chromosome is typically conserved, the W is always smaller, with variations in size and morphology between species. Here, we report an analysis of the satellitome of Triportheus auritus (TauSat) by integrating genomic and chromosomal data, with a special focus on the highly abundant and female-biased satDNAs. In addition, we investigated the evolutionary trajectories of the ZW sex chromosomes in the Triportheidae family by mapping satDNAs in selected representative species of this family. The satellitome of T. auritus comprised 53 satDNA families of which 24 were also hybridized by FISH. Most satDNAs differed significantly between sexes, with 19 out of 24 being enriched on the W chromosome of T. auritus. The number of satDNAs hybridized into the W chromosomes of T. signatus and T. albus decreased to six and four, respectively, in accordance with the size of their W chromosomes. No TauSat probes produced FISH signals on the chromosomes of Agoniates halecinus. Despite its apparent conservation, our results indicate that each species differs in the satDNA accumulation on the Z chromosome. Minimum spanning trees (MSTs), generated for three satDNA families with different patterns of FISH mapping data, revealed different homogenization rates between the Z and W chromosomes. These results were linked to different levels of recombination between them. The most abundant satDNA family (TauSat01) was exclusively hybridized in the centromeres of all 52 chromosomes of T. auritus, and its putative role in the centromere evolution was also highlighted. Our results identified a high differentiation of both ZW chromosomes regarding satellites composition, highlighting their dynamic role in the sex chromosomes evolution.

Chromosomal Evolution of Suboscines: Karyotype Diversity and Evolutionary Trends in Ovenbirds (Passeriformes, Furnariidae).

Furnariidae (ovenbirds) is one of the most diversified families in the Passeriformes order and Suboscines suborder. Despite the great diversity of species, cytogenetic research is still in its early stages, restricting our knowledge of their karyotype evolution. We combined traditional and molecular cytogenetic analyses in three representative species, Synallaxis frontalis, Syndactyla rufosuperciliata, and Cranioleuca obsoleta, to examine the chromosomal structure and evolution of ovenbirds. Our findings revealed that all the species studied had the same diploid number (2n = 82). Differences in chromosomal morphology of some macrochromosomes indicate the presence of intrachromosomal rearrangements. Although the three species only had the 18S rDNA on one microchromosome pair, chromosomal mapping of six simple short repeats revealed a varied pattern of chromosome distribution among them, suggesting that each species underwent different repetitive DNA accumulation upon their divergence. The interspecific comparative genomic hybridization experiment revealed that the Furnariidae species investigated carry centromeric regions enriched in similar repetitive sequences, bolstering the Furnariidae family's karyotype conservation. Nonetheless, the outgroup species Turdus rufiventris (Turdidae) demonstrated an advanced stage of sequence divergence with hybridization signals that were almost entirely limited to a few microchromosomes. Overall, the findings imply that Furnariidae species have a high degree of chromosomal conservation, and we could also observe a differentiation of repetitive sequences in both Passeriformes suborders (Suboscines and Oscines).

Cytogenetic Evidence Clarifies the Phylogeny of the Family Rhynchocyclidae (Aves: Passeriformes).

The phylogenetic position and taxonomic status of Rhynchocyclidae (Aves: Passeriformes) have been the subject of debate since their first description. In most models, Rhynchocyclidae represents a subfamily-level taxon placed within the Tyrant Flycatchers (Tyrannidae). Considering that this classification does not include cytotaxonomic characters, we tested the hypothesis that the chromosome organization of Rhynchocyclidae members differs from that of Tyrannidae. Hence, we selected two species, Tolmomyias sulphurescens, and Pitangus sulphuratus, representing Rhynchocyclidae and Tyrannidae, respectively. Results revealed a diploid number (2n) of 60 in T. sulphurescens and 2n = 80 in P. sulphuratus, indicating significant chromosomal differences. Chromosome mapping of Gallus gallus (GGA) and Taeniopygia guttata bacterial artificial chromosome (BAC) corresponding to chromosomes GGA1-28 (except 16) revealed that the genome evolution of T. sulphurescens involved extensive chromosome fusions of macrochromosomes and microchromosomes. On the other hand, P. sulphuratus retained the ancestral pattern of organization of macrochromosomes (except the centric fission involving GGA1) and microchromosomes. In conclusion, comparing our results with previous studies in Tyrant Flycatchers and allies indicates that P. sulphuratus has similar karyotypes to other Tyrannidae members. However, T. sulphurescens does not resemble the Tyrannidae family, reinforcing family status to the clade named Rhynchocyclidae.

Against the mainstream: exceptional evolutionary stability of ZW sex chromosomes across the fish families Triportheidae and Gasteropelecidae (Teleostei: Characiformes).

Teleost fishes exhibit a breath-taking diversity of sex determination and differentiation mechanisms. They encompass at least nine sex chromosome systems with often low degree of differentiation, high rate of inter- and intra-specific variability, and frequent turnovers. Nevertheless, several mainly female heterogametic systems at an advanced stage of genetic differentiation and high evolutionary stability have been also found across teleosts, especially among Neotropical characiforms. In this study, we aim to characterize the ZZ/ZW sex chromosome system in representatives of the Triportheidae family (Triportheus auritus, Agoniates halecinus, and the basal-most species Lignobrycon myersi) and its sister clade Gasteropelecidae (Carnegiella strigata, Gasteropelecus levis, and Thoracocharax stellatus). We applied both conventional and molecular cytogenetic approaches including chromosomal mapping of 5S and 18S ribosomal DNA clusters, cross-species chromosome painting (Zoo-FISH) with sex chromosome-derived probes and comparative genomic hybridization (CGH). We identified the ZW sex chromosome system for the first time in A. halecinus and G. levis and also in C. strigata formerly reported to lack sex chromosomes. We also brought evidence for possible mechanisms underlying the sex chromosome differentiation, including inversions, repetitive DNA accumulation, and exchange of genetic material. Our Zoo-FISH experiments further strongly indicated that the ZW sex chromosomes of Triportheidae and Gasteropelecidae are homeologous, suggesting their origin before the split of these lineages (approx. 40-70 million years ago). Such extent of sex chromosome stability is almost exceptional in teleosts, and hence, these lineages afford a special opportunity to scrutinize unique evolutionary forces and pressures shaping sex chromosome evolution in fishes and vertebrates in general.

Karyotype Evolution and Genomic Organization of Repetitive DNAs in the Saffron Finch, Sicalis flaveola (Passeriformes, Aves).

The Saffron finch (Sicalis flaveola), a semi-domestic species, is tolerant of human proximity and nesting in roof spaces. Considering the importance of cytogenomic approaches in revealing different aspects of genomic organization and evolution, we provide detailed cytogenetic data for S. flaveola, including the standard Giemsa karyotype, C- and G-banding, repetitive DNA mapping, and bacterial artificial chromosome (BAC) FISH. We also compared our results with the sister groups, Passeriformes and Psittaciformes, bringing new insights into the chromosome and genome evolution of birds. The results revealed contrasting rates of intrachromosomal changes, highlighting the role of SSR (simple short repetition probes) accumulation in the karyotype reorganization. The SSRs showed scattered hybridization, but brighter signals were observed in the microchromosomes and the short arms of Z chromosome in S. flaveola. BACs probes showed conservation of ancestral syntenies of macrochromosomes (except GGA1), as well as the tested microchromosomes. The comparison of our results with previous studies indicates that the great biological diversity observed in Passeriformes was not likely accompanied by interchromosomal changes. In addition, although repetitive sequences often act as hotspots of genome rearrangements, Passeriformes species showed a higher number of signals when compared with the sister group Psittaciformes, indicating that these sequences were not involved in the extensive karyotype reorganization seen in the latter.

Interspecies Chromosome Mapping in Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes (Aves): Cytogenomic Insight into Microchromosome Organization and Karyotype Evolution in Birds.

Interchromosomal rearrangements involving microchromosomes are rare events in birds. To date, they have been found mostly in Psittaciformes, Falconiformes, and Cuculiformes, although only a few orders have been analyzed. Hence, cytogenomic studies focusing on microchromosomes in species belonging to different bird orders are essential to shed more light on the avian chromosome and karyotype evolution. Based on this, we performed a comparative chromosome mapping for chicken microchromosomes 10 to 28 using interspecies BAC-based FISH hybridization in five species, representing four Neoaves orders (Caprimulgiformes, Piciformes, Suliformes, and Trogoniformes). Our results suggest that the ancestral microchromosomal syntenies are conserved in Pteroglossus inscriptus (Piciformes), Ramphastos tucanus tucanus (Piciformes), and Trogon surrucura surrucura (Trogoniformes). On the other hand, chromosome reorganization in Phalacrocorax brasilianus (Suliformes) and Hydropsalis torquata (Caprimulgiformes) included fusions involving both macro- and microchromosomes. Fissions in macrochromosomes were observed in P. brasilianus and H. torquata. Relevant hypothetical Neognathae and Neoaves ancestral karyotypes were reconstructed to trace these rearrangements. We found no interchromosomal rearrangement involving microchromosomes to be shared between avian orders where rearrangements were detected. Our findings suggest that convergent evolution involving microchromosomal change is a rare event in birds and may be appropriate in cytotaxonomic inferences in orders where these rearrangements occurred.

Cytotaxonomy of Gallinula melanops (Gruiformes, Rallidae): Karyotype evolution and phylogenetic inference.

Although Rallidae is the most diverse family within Gruiformes, there is little information concerning the karyotype of the species in this group. In fact, Gallinula melanops, a species of Rallidae found in Brazil, is among the few species studied cytogenetically, but only with conventional staining and repetitive DNA mapping, showing 2n=80. Thus, in order to understand the karyotypic evolution and phylogeny of this group, the present study aimed to analyze the karyotype of G. melanops by classical and molecular cytogenetics, comparing the results with other species of Gruiformes. The results show that G. melanops has the same chromosome rearrangements as described in Gallinula chloropus (Clade Fulica), including fission of ancestral chromosomes 4 and 5 of Gallus gallus (GGA), beyond the fusion between two of segments resultants of the GGA4/GGA5, also fusions between the chromosomes GGA6/GGA7. Thus, despite the fact that some authors have suggested the inclusion of G. melanops in genus Porphyriops, our molecular cytogenetic results confirm its place in the Gallinula genus.