Cytologia 43: 249-253, 1978

A karyosystematic Study in Columbiformes(Ayes)

Edmundo Jose de Lucca Departamento de Genetica, Faculdade de Ciencias Medicas e Biologicasde Botucatu, SP, Brasil

and

Margarida Lopes Rodrigues de Aguiar Departamento de Genetica, Escola Superior de Agricultura "Luiz de Queiroz" , Piracicaba, SP, Brasil

Received August 19, 1976

Bird systematics based on morphological and anatomical characters are in some cases controversial (Hammar 1970). One of these cases concerns the classifi cation proposed by Goodwin (1959, 1970), Pinto (1964), Johnston (1961), Hellmayr and Conover (1942) and Peters (1937) for Columbiformes belonging to Columbina and Columbigallina genera (see Table 1). The comparative analysis of the karyotype of closely related species has helped the understanding of the mechanisms of chromosomal evolution and phylogenetic relationships in animals. The major problem is to know how to limit the use of the karyotype since species with identical karyotypes may be included in the same systematic unit and species with distinct differences may be arranged from their karyotypes (Hammar 1970). The present report presents the karyotypes of four species of Brazilian Columbi formes belonging to the Columbina genus (according to Goodwin 1970) in an attempt to reach better systematic classification.

Materials and methods Four species belonging to the Columbina genus were analysed: C. picui: 1 male and I female; C. minuta: 2 males; C. passerina: 2 males and C. talpacoti: 2 males and 2 females. The specimens were collected in differents localities in Brazil and classified according to Goodwin (1970).

The chromosome preparations were made as previously described by Lucca

(1971). The animals were injected with a 0.5% colchicine solution (0.02ml/g of animal weight). Small pieces of spleen, liver and gonads were pretreated in distilled water for 10 minutes, fixed in 50% acetic acid and squashed . The slides were air dried, hydrolised in 1N HCl at 60•Ž for 10 minutes and stained in Giemsa.

The metaphases were photographed with a Zeiss photomicroscope at a magnifi cation of 400•~. For morphometric analyses of the karyotypes the prints were magnified to 3000•~. All chromosomes were considered in this analysis. Relative lenghts were calculated as a percent of the haploid autosome set plus one Z chromo- 250 E. J. De Lucca and M. L. R. De Aguiar Cytologia 43

some. Centromere position was designated according to Levan, Fredga and Sandberg (1964).

Results

Table 2 shows the values of relative length and arm ratio of the macrochromo

- somes of the species investigated. Figure 1 shows the karyotype of C. picui. The 2n chromosome number is about 76, with a continuous reduction in chromosome length from about 4.24ƒÊ to

Table 1. Columbina and Columbigallina genera recognized by Peters (1937), Hellmayr and Conover (1942), Johnston (1961), Pinto (1964) and Goodwin (1959, 1970)

* Described as belonging to Scardafella genus by all the other authors. ** Described as belonging to Oxypelia genus by all the others authors.

Table 2. Average relative length and arm ratio of the chromosomes of the species analysed

about 0.2ƒÊ. Chromosomes 1 and 7 are metacentric and all the others have terminal centromere. The Z chromosome is also a telocentric chromosome. It is no. 4, about 2.0ƒÊ long. The W chromosome is a submetacentric chromosome about

0.9ƒÊ long. Its size is between chromosomes no. 7 and no. 8. Figures 2, 3 and 4 show, respectivelly, the karyotypes of C. minuta, C. passerina and C. talpacoti. The diploid number of chromosomes is about 76 for all of them and the chromosome lengths vary from about 4.5ƒÊ to about 0.3ƒÊ. The first eight pairs can be identified by their size and arm ratio and the karyotypes of C. minuta, C. 1978 A karyosystematic Study in Columbiformes (Ayes) 251

passerina and C. talpacoti are quite similar. Only in C. talpacoti there is informa tion about sex chromosomes: Z chromosome, no. 4, is metacentric about 2.0ƒÊ long; W chromosome, with subterminal centromere, is about 0.9ƒÊ long, ranging in size between no. 7 and 8.

Discussion

A species can only be defined by a whole array of morphological, physiological and behavioural features. Overemphasis on a few morphological characters has led to a certain amount of ambiguity and confusion in the delineation of species in different groups of animals. It is expected that the karyotypes will provide us with

Figs. 1-4. 1, karyotype of female Columbina picui 2n=76. 2, karyotype of male C. minuta 2n=76. 3, karyotype of male C. passerina 2n=76. 4, karyotype of female C. talpacoti 2n=76.

an additional means of assessing the evolutionary patterns and pathways that have led to natural group assemblages. Cytotaxonomical studies in different groups of mammals among vertebrates have been carried out extensively with a good deal of success but such attempts have rarely been made in birds. The great number of microchromosomes still causes some difficulties for an accurate count of the chromosomes. The presence of macro -chromosomes, clearly distinguishable cytologically, is a distinct advantage for com - parison of chromosomes of groups of birds of different taxonomical categories. This should enable us to derive possible homologies between chromosomes of different species. According to Hammar (1970) bird karyotypes are very conser vative and therefore suitable for systematic classification of certain species. 252 E. J. De Lucca and M. L. R. De Aguiar Cytologia 43

Only in a few papers the chromosome complements of birds have been used in taxonomy and for clarification of phylogenetic relationships. Probably, one of the major reasons for this is a lack of comparative taxonomical data of closely related species. Yamashina (1952) and Hammar (1970) discussed the systematics of the family Anatidae based on karyotypes and hybridization studies. According to Yamashina (1952), the genera Anser and Brantha were included in the subfamily Anserinae and the genera Anas, Cygnus, Dendronessa and Mergus, in the subfamily Anatinae. Hammar (1970) included in the subfamily Anserinae the genera Anser, Brantha and Cyguns based on karyotypes and hybridization studies (Gray 1958). The analysis of Bucephala clangula's karyotype enable Hammar (1970) to transfer this species to a new subfamily, Bucephalinae. According to Ray-Chauduhri (1973), Bucephala is taxonomically closer to Mergus and belongs to the tribe Mergini. Hammar (1970) suggested that Mergus can also be included in the subfamily Bucephalinae. Hybrid between these two genera have been found (Gray 1958) repeatedly in the wild state thus indicating their close affinity. In Columbidae, Makino et al. (1956) described the karyotypes of Columba, Streptopelia, Sphenurus and Zenaidura genera and observed that there is a close karyological similarity among Columba, Sphenurus and Streptopelia and between Streptopelia and Zenaidura. This is an indication of a close affinity existing in their taxonomical relationships too. In 48 species, belonging to 12 different orders, Takagi and Sasaki (1974) obtained some important findings relevant to current taxonomic controversies in birds and the authors suggested that the karyotype furnishes phylogenetic evidence independent from anatomical and physiological characteristics. The present investigation shows remarkable differences between the karyotypes of C. picui (Fig. 1) and the three other species: C. minuta (Fig. 2), C. passerina (Fig. 3) and C. talpacoti (Fig. 4). In the four species the 2n chromosome number (2n=76) is similar, but in C. picui there is a predominance of subtelocentric and telocentric, whereas in the three other species most of the macrochromosomes are metacentric and submetacentric. Furthermore, in C. picui some of the macrochromosomes are rather smaller than the correspondent ones in the three other species. Here pericentric inversions could be one of the mechanisms involved in the diversifica tion of C. picui. As said before, bird systematics based on morphological and anatomical charac ters are in some cases controversial and in this case the karyotype may be a very good 'criterion for classification. Based on this assumption, most probably C. picui is the only one representative species of the Columbina genus as was proposed by Peters (1937), Hellmayr and Conover (1942) and Pinto (1964) and the three other species seem to belong to Columbigallina genus, because the karyotype of C. picui looks very different from that of C. minuta, C. passerina and C. talpacoti. Further extensive cytogenetic analyses together with morphological, serological, ethological and hybridization studies will be certainly useful to solve this systematic problem in Columbiformes. 1978 A karyosystematic Study in Columbiformes (Ayes) 253

Summary

The karyotypes of four species of Columbiformes have been analysed. The use of the karyotypes as a tool to help solving the problem of systematic classifica tion is discussed. The cytogenetic date obtained agree with the separation of C. picui, in the Columbina genus, from C. minuta, C. passerina and C. talpacoti, in the Columbigallina genus.

References

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