Chromosomal painting in Charadrius collaris Vieillot, 1818 and Vanellus chilensis Molina, 1782 and an analysis of chromosomal signatures in Charadriiformes

Abstract

Charadriiformes represent one of the largest orders of birds; members of this order are diverse in morphology, behavior and reproduction, making them an excellent model for studying evolution. It is accepted that the avian putative ancestral karyotype, with 2n = 80, remains conserved for about 100 million years. So far, only a few species of Charadriiformes have been studied using molecular cytogenetics. Here, we performed chromosome painting on metphase chromosomes of two species of Charadriidae, Charadrius collaris and Vanellus chilensis, with whole chromosome paint probes from Burhinus oedicnemus. Charadrius collaris has a diploid number of 76, with both sex chromosomes being submetacentric. In V. chilensi a diploid number of 78 was identified, and the Z chromosome is submetacentric. Chromosome painting suggests that chromosome conservation is a characteristic common to the family Charadriidae. The results allowed a comparative analysis between the three suborders of Charadriiformes and the order Gruiformes using chromosome rearrangements to understand phylogenetic relationships between species and karyotypic evolution. However, the comparative analysis between the Charadriiformes suborders so far has not revealed any shared rearrangements, indicating that each suborder follows an independent evolutionary path, as previously proposed. Likewise, although the orders Charadriiformes and Gruiformes are placed on sister branches, they do not share any signature chromosomal rearrangements.

Fig 1. Map of geographical distribution of Charadrius collaris and Vanellus chilensis, with their respective collection locations.

Charadrius collaris: 1-Island of Otelina; 2- Pilão beach; Vanellus chilensis: 3-Belém Airport. The map was prepared using the QUANTUM-GIS software, v. 2.10.1 (https://qgis.org). The free database was obtained from DIVA-GIS (https://www.diva-gis.org).

Fig 2. G-banding in Charadrius collaris (2n = 76) showing the homologies of whole chromosome probes of Burhinus oedicnemus (right).

(*) Macrochromosome probes reveal homeology to the sex chromosome W. The microchromosomes are arranged sequentially, as the correct homeologies cannot be detected due to the lack of reliable markers.

Fig 3. Chromosomal painting of whole chromosome probes of Burhinus oedicnemus on Charadrius collaris.

The probes are visualized with avidin-Cy3 (red); chromosomes counterstained with DAPI (blue).

Fig 4. G-banding in Vanellus chilensis (2n = 78) showing the homologies of whole chromosome probes of Burhinus oedicnemus (right).

The microchromosomes are arranged sequentially as the correct homeologies cannot be detected due to lack of reliable markers.

Fig 5. Chromosomal painting of whole chromosome probes of Burhinus oedicnemus homologous to macrochromosomes in Vanellus chilensis.

The probes are visualized with avidin-Cy3 (red); chromosomes counter-stained with DAPI (blue).

Fig 6. Idiogram for chromosomal pairs that have undergone pericentric inversions or centric fusions.

Pericentric inversion that differ: A) BOE3 from CCO3; B) BOE6 from CCO6; C) Pericentric inversion of the metacentric CCO8 and the acrocentric BOE9; D) Fusion of CCO9 and CCO10 giving rise to BOE8.

Fig 7. Phylogeny of Charadriiform and Gruiform Orders modified from original publications [1, 21].

Chromosomal data: Gruiformes [16, 20, 21, 31]; Burhinus [13]; Vanellus [11; present work]; Charadrius (present work); Jacana [17]; Actitis [18]; Scolopax [19]; Larus [16]; PAK [4]. The numbers under the rearranged chromosomes refer to the karyotypes described by the respective authors. Only the diploid numbers of the genera analyzed by molecular cytogenetics are presented. M = microchromosome;? = Doubt about the location of the rearrangements; PAK: Avian Putative Ancestral Karyotype; GPAK: Gruiformes Putative Ancestral Karyotype; CPAK: Charadriiformes Putative Ancestral Karyotype. The karyotypes CPAK and GPAK are the same as PAK because there are no common rearrangements among the analyzed clades (Gruiformes, Charadrii, Scolopaci and Lari).