Peaceful revolution in genome size: polyploidy in the Nabidae (Heteroptera); autosomes and nuclear DNA content doubling

Abstract

Abstract Genome size and the position of 18S ribosomal DNA (rDNA) were analysed in two Himacerus, eight Nabis and two Prostemma species from the family Nabidae using flow cytometry and fluorescence in situ hybrization techniques. The karyotypes of Nabis biformis and Nabis maoricus, each with 2n = 16 + XY, and Prostemma aeneicolle, with 2n = 26 + XY, were recorded for the first time. All the species displayed one or two 18S rDNA signals on the X chromosome and up to two signals on the Y chromosome. Several females exhibited two different types of X chromosome breakage, namely within or outside of the 18S rDNA region. Measurements of nuclear DNA content revealed significant differences between all three genera under study. Most notably, the nuclear DNA content of Himacerus species, with 2n = 32/36 + XY (2C = 9–10 pg), was double that of Nabis species, with 2n = 16 + XY (2C = 4–6 pg). Therefore, the previously rejected theory of an autosomal polyploidy event in the evolution of the genus Himacerus is strongly supported by the results of the present study and is now being resurrected.