G-Band Polymorphism in Natural Populations of Yellow-Legged Green Pigeon, Treron phoenicoptera phoenicoptera from Northern India

Abstract

In the present study, 48 individuals of common or yellow-legged green pigeon, Treron phoenicoptera phoenicoptera (Latham), belonging to the family Columbidae of the order Columbiformes were utilized for the analysis of G-banding patterns. The birds were sampled from different geographical areas which have been grouped as three distinct populations. Population A consists of birds from Allahabad. Populations B and C consist of birds from Chotanagpur Division and Singhbhum Division of Jharkhand, respectively. Besides these individuals a single female bird from Berhampur (district Ganjam) of coastal Odisha has also been karyotyped. The diploid complement comprises of 74 chromosomes which consists seven pairs of macrochromosomes (including the sex chromosomes) and thirty pairs of microchromosomes. The bird was found to be polymorphic for chromosome pairs 1 and 2. The chromosome pair 1 was present either in a metacentric (1m) or a subtelocentric (1st) condition. Similarly chromosome 2 was also present as either a subtelocentric (1st) or a metacentric (2m). The polymorphism was explained on the basis of two independent pericentric inversions involving chromosome pairs 1 and 2. With two chromosomes, involved karyomorphs were in inversions, ideally there should be nine types of karyomorphs. In the present investigation five different karyomorphs were encountered. GTG banding (G-bands by trypsin using Giemsa) method of Seabright (Lancet 2:971–972, 1971) was adopted with some modifications. All the karyomorphs were subjected to G-banding analysis, however, consistent and reasonably good G-bands were produced only in karyomorphs 1m1m/2st2m, 1m1m/2st2st, 1st1st/2st2m of population A., 1m1m/2st2m, of population B, 1m1m/2st2st and 1m1m/2st2m of population C and 1m1m/2st2m of Berhampur, Odisha. The G-banding patterns are based on observations of ten metaphase plates of each karyomorphs. Thus, the idiogram showing schematic presentation of G-bands are based on the chromosomes showing minimal condensation which reveal optimum number of bands. The idiogram depicting G-bands have been constructed using the relative length (LR) and centromeric indices (IC) data. In G-banded chromosomes, the band nomenclature has been done according to the guidelines of Paris Conference (1971) and supplement (1975) for human chromosomes. The G-band pattern analysis revealed the presumed breakpoints in the chromosome pairs 1 and 2 lending further support to the pericentric inversions in these chromosome pairs. The banding sequence of the rearranged chromosome (1st) can be described as: $$ {\text{pter}} \to {\text{p22}}::{\text{q12}} - {\text{p22}}::{\text{q12}} \to {\text{qter}}. $$ The banding sequence of the rearranged chromosome (2m) can be described as: $$ {\text{pter}} \to {\text{p12}}::{\text{q21}} - {\text{p12}}::{\text{q21}} \to {\text{qter}}. $$ The G-banding patterns of the macrochromosomes has also been discussed.