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.

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

“…Previously, analyzing the macrochromosomes using chromosome painting, we proposed that, after divergence, each shorebird suborder underwent different chromosome rearrangements [ 13 ], which was later confirmed by others [ 12 ]. Here, we extended this hypothesis to microchromosomes as well.…”

“…chilensis and C . collaris , Pinheiro et al [ 12 ] found differences in the microchromosomes with FISH signals using Burhinus oedicnemus probes corresponding to microchromosomes. These authors suggested that the variation in the number of signals was indicative of the considerable number of rearrangements involving microchromosomes in V .…”

“…The first detailed studies focused on chromosome organization among shorebirds came from chromosome painting data using different sets of paints: Gallus gallus [ 6 , 9 ], B . oedicnemus [ 6 , 10 , 11 , 12 ], Leucopternis albicollis [ 9 ], and Zenaida auriculata [ 13 ]. These studies revealed extensive chromosome reorganization in some species, while others retained a conserved karyotype, similar to the putative avian ancestral karyotype.…”

“…In Larus argentatus (Clade Lari), only fusions of macrochromosomes with microchromosomes were detected [ 10 ]. On the other hand, Charadrius collaris and Vanellus chilensis , both included in the Clade Charadrii, have a typical avian karyotype [ 9 , 12 ].…”

“…Although B . oedicnemus provides insights about rearrangements involving microchromosomes, the exact role of these small elements in the rearrangements were not identified [ 10 , 11 , 12 ]. An alternative approach to investigate the microchromosome organization is bacterial artificial chromosomes (BACs) derived from chicken and zebra finch.…”