Phylogenetic Implications of Karyotypic Characters of Parasitic Hymenoptera

Abstract

Karyotypic data show that n = 14–17 should be considered as the initial chromosome number for parasitic wasps. Apparently, the same values are initial for aculeate Hymenoptera, with the chromosome number being substantially reduced at least in the family Dryinidae. A parallel decrease in chromosome number occurred independently and repeatedly in Ichneumonidae, Braconidae and Microhymenoptera. Low chromosome numbers (n = 9–11) are a synapomorphy of Diaprioidea, Cynipoidea, Platygastroidea, Ceraphronoidea and Chalcidoidea. In addition, chromosome numbers were reduced to n = 5–6 in several groups of Chalcidoidea. Following main trends of evolutionary change of karyotypes of parasitic wasps are found: (1) decrease in the chromosome number through tandem fusions (less frequently, centric ones) and (2) karyotypic dissymmetrisation through an increase in the size differentiation of chromosomes and/or in the proportion of acrocentrics in the karyotype.