article 18 chromosome polymorphism nonhuman 16 karyotype 12 animal cell 10 natural population 10 Animalia 8 argentina 8 chromosome inversion 8 Animals 6 Polymorphism, Genetic 6 male 6 natural selection 6 population genetics 6 species 6 Argentina 4 Belostoma 4 Belostomatidae 4 Body Constitution 4 Drosophila 4 Drosophila buzzatii 4 Hemiptera 4 Heteroptera 4 Insecta 4 Inversion, Chromosome 4 Orthoptera 4 X chromosome 4 Y chromosome 4 body size 4 chromosome variant 4