RESUMO
Drosophila pseudoobscura populations of Central Mexico are chromosomally highly polymorphic. Five gene arangements in the third chromosome are endemic, including the two newly described in the present article. The phylogenetic tree of the gene arrangements known in the species is shown in Figure 1. The ones found in Central Mexico all belong to the Santa Cruz "phylad", while in the northern part of the species area both Santa Cruz and Standard phylads are widespread. Some inferences concerning the evolutionary history of the species are presented.
Assuntos
Cromossomos , Drosophila , Polimorfismo Genético , Animais , Mapeamento Cromossômico , Genética Populacional , Cariotipagem , MéxicoAssuntos
Aberrações Cromossômicas , Drosophila , Infertilidade Masculina/genética , Cromossomos Sexuais , Animais , Cromossomos , Colômbia , Troca Genética , Citoplasma , Feminino , Fertilidade , Frequência do Gene , Genes Dominantes , Genes Recessivos , Células Germinativas/citologia , Hibridização Genética , Cariotipagem , Masculino , MutaçãoRESUMO
A comparative study of genic allozyme and chromosomal polymorphisms in four continental (South American) and six oceanic island (West Indies) populations of Drosophila willistoni has been made. The pattern of genic polymorphism is closely similar in all populations. Although regional and local differences in gene frequencies are found, generally the same alleles occur at high, intermediate, and low frequencies in all populations. An average individual is heterozygous at 18.4 and 16.2% of its loci in the continental and island populations, respectively. By contrast, chromosomal polymorphism is sharply reduced on the islands compared to most continental populations, and some chromosomal inversions are more frequent on some islands than on others. The observations are not compatible with the hypothesis that most of the gene variants are adaptively neutral. Balancing natural selection is responsible for most of the genic polymorphism in natural populations of D. willistoni.