Chromosomes of parasitic wasps of the superfamily Chalcidoidea (Hymenoptera): An overview

Abstract

An overview of the current knowledge of chromosome sets of the parasitoid superfamily Chalcidoidea is given. Karyotypes of approximately 240 members of this group, i.e. just above one percent of described species, are studied up to now. Techniques for obtaining and analyzing preparations of chalcid chromosomes are outlined, including the so-called "traditional" and "modern" methods of differential staining as well as fluorescence in situ hybridization (FISH). Among the Chalcidoidea, the haploid chromosome number can vary from n = 3 to n = 11, with a clear mode at n = 6 and a second local maximum at n = 10. In this group, most chromosomes are either metacentric or submetacentric, but acrocentrics and/or subtelocentrics also can predominate, especially within karyotypes of certain Chalcidoidea with higher chromosome numbers. The following main types of chromosomal mutations are characteristic of chalcid karyotypes: inversions, fusions, translocations, polyploidy, aneuploidy and B chromosome variation. Although karyotype evolution of this superfamily was mainly studied using phylogenetic reconstructions based on morphological and/or molecular characters, chromosomal synapomorphies of certain groups were also revealed. Taxonomic implications of karyotypic features of the Chalcidoidea are apparently the most important at the species level, especially among cryptic taxa.

Keywords: FISH; base-specific fluorochromes; chalcid wasps; differential staining; karyotypes; phylogeny; taxonomy.

Figure 1.

Distribution of main lineages of Chalcidoidea by the chromosome number at the species level (based on data from Table 1).

Figure 2.

Representative karyotypes of ChalcidoideaaTrichogrammaprincipium Sugonjaev & Sorokina, 1976 (Trichogrammatidae; n = 5) bMesopolobusmediterraneus (Mayr, 1903) (Pteromalidae; 2n = 10) cOomyzusgallerucae (Fonscolombe, 1832) (Eulophidae; 2n = 12) dEurytomacynipsea Boheman, 1836 (Eurytomidae; 2n = 20 + 4B). Scale bar: 10 µm.

Figure 3.

Variation ranges of chromosome numbers of Chalcidoidea mapped on the phylogenetic tree of chalcid families (simplified from Heraty et al. 2013). Most frequent chromosome numbers for certain taxa are given in brackets (redrawn from Gokhman 2013 and updated with data from Table 1).