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

Abstract

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.

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

“…The main rearrangements were fusion events, including macro-and microchromosome. In Syrigma sibilatrix, the GGA8, GGA9, and GGA10 chromosome paints hybridized to the long arms of biarmed macrochromosomes, also indicating fusions with microchromosomes [100]. Although BOE and chicken (GGA) microchromosome paints do not allow for the identification of the exact microchromosome involved in the fusion events, these studies indicated that fusion events involving these tiny chromosomes are nonetheless frequent among Pelecaniformes.…”

“…Molecular cytogenetics is still scarce in this order; however, recent studies using chromosome painting with chicken and/or stone curlew (B. oedicnemus, BOE) paints indicated that the karyotype of Pelecaniformes is reorganized, similar to that of the parrots and falcons [99,100]. The stone curlew chromosome painting in three Pelecaniformes species (Ardea cinerea, Egretta garzetta, and Nipponia nippon) indicated that different chromosome rearrangements occur in different Pelecaniformes lineages [99].…”