The chromosomes of Diprion pini and D-similis (Hymenoptera : Diprionidae):implications for karyotype evolution

Earlier cytological investigations characterize the family Diprionidae with a modal chromosome number of seven. This study shows that Diprion pini and D. similis have 14 acrocentric chromosomes (n = 14 for haploid males and 2 n = 28 for diploid females). In D. pini, rRNA genes are located on the sate llite and the round short arm of the chromosome carrying this segment. We s tudied six populations with no evidence of chromosomal polymorphism at the species level. Our results disagree with those published previously and reo pen the question of karyotype evolution. Chromosome morphology, ISH and C-b anding results support the hypothesis of chromosome number doubling by cent ric fission and not by polyploidization, followed by the growth of short ar ms by means of pericentromeric DNA amplification.