Chromosomal analysis in Cathartidae: distribution of heterochromatic blocks and rDNA, and phylogenetic considerations

Abstract

Three species of Cathartidae (Sarcoramphus papa, Cathartes aura and Cathartes burrovianus) were cytogenetically characterized by G- and C-banding. 18S-28S rDNA was used as a probe to map major ribosomal clusters. These species showed very similar karyotypes, with 2n = 80, 10 pairs of macrochromosomes, a submetacentric Z and a metacentric W chromosome. However, differences were found in the amount and distribution of heterochromatic blocks: S. papa showed heterochromatin only in the pericentromeric region and in chromosome W, while both species of Cathartes had heterochromatic blocks also in the long arm of two acrocentric pairs. Ribosomal clusters were found in a small pair in all three species. Karyotype analysis in Cathartidae revealed that this family has retained similarities to the putative avian ancestral karyotype, and placed Cathartidae in a more basal position in relation to Accipitridae and Falconidae. However, the cytogenetic data still cannot clarify the phylogenetic relationship between this family and other groups, such as Ciconiidae, considered its sister-group according to nucleic acid hybridization studies.

Chromosome Painting in Tyrant Flycatchers Confirms a Set of Inversions Shared by Oscines and Suboscines (Aves, Passeriformes)

“…S. icterophrys and P. sulphuratus show only 1 pair of microchromosomes with 18S rDNA. This is the most common situation observed among birds, including basal groups such as G. gallus [Ladjali-Mohammedi et al, 1999], and also in other Passeriformes [Kretschmer et al, 2014;dos Santos et al, 2015] and New World vultures [Tagliarini et al, 2009]. This condition -1 cluster of 18S rDNA located in a pair of microchromosomes -seems to be a plesiomorphic state, while a higher number of clusters represent a derived state, as in the case of S. subcristata , in which we found 2 pairs of microchromosomes with clusters of 18S rRNA genes.…”

“…Most birds have been shown to possess constitutive heterochromatin concentrated in the pericentromeric regions and, as a rule, in the W chromosome. The exceptions so far are related to the enlargement of sex chromosomes, such as in Piciformes and in Myiopsitta monachus de Oliveira Furo et al, 2017] and in species of New World vultures [Tagliarini et al, 2007[Tagliarini et al, , 2009. With regard to telomeric sequences, it was observed that some species of birds show numerous interstitial telomeric sequences, especially in Ratites [Nanda et al, 2002].…”

Phylogenetic Position of Avian Nocturnal and Diurnal Raptors

“…Because Turkey Vulture ( Cathartes aura ) generated a long branch, it was removed after preliminary analysis (see Gibb et al 2007; Slack et al 2007). This could be partly because Cathartidae is possibly not a genuine raptor and its resemblance to Old World vultures is an example of convergent evolution (Tagliarini et al 2009). Here again, additional sequences, including nuclear data, will be helpful.…”

Chromosome Painting in <b><i>Trogon s. surrucura</i></b> (Aves, Trogoniformes) Reveals a Karyotype Derived by Chromosomal Fissions, Fusions, and Inversions

“…According to Schartl et al [2016], large and heterochromatic W chromosomes in different lineages of Neoaves arose by the accumulation of repetitive sequences and their retention due to low degeneration rates of the W chromosome. In fact, a case of homomorphic sex chromosomes has recently been found in Myiopsitta monachus (Psittaciformes, Psittacidae), and microsatellite probes revealed an accumulation of 3 different [Nishida-Umehara et al, 2007;Tagliarini et al, 2009]. However, some species have more than 1 pair of chromosomes carrying 18S rDNA, and this feature is considered to be a derived state.…”