Chromosomal organization of different repetitive sequences in four wasp species of the genus Trypoxylon Latreille (Hymenoptera: Crabronidae) and insights into the composition of wasp telomeres.

Abstract

This study characterizes the chromosomal organization of DNA repetitive sequences and the karyotypic evolution in four representatives of the solitary wasp genus Trypoxylon using conventional and molecular cytogenetic techniques. Our findings present the first cytogenetic data for T. rogenhoferi (2n=30) and T. albonigrum (2n=32) while the karyotypes of T. nitidum (2n=30) and T. lactitarse (2n=30) were similar to those described previously. Fluorochrome staining and microsatellite distribution data revealed differences in the constitutive heterochromatin composition among species. Trypoxylon nitidum and T. albonigrum exhibited a single rRNA gene site, potentially representing an ancestral pattern for aculeate Hymenoptera, while T. rogenhoferi and T. lactitarse showed two pericentromeric rRNA gene sites, suggesting amplification events in their ancestral clade. The (TCAGG)n motif hybridized in the terminal regions of the chromosomes in all four Trypoxylon species, which may suggest that this sequence is part of their telomeres. Notably, the presence of this repetitive sequence in the centromeric regions of certain chromosome pairs in two species supports the hypothesis of chromosomal fusions or inversions in the ancestral karyotype of Trypoxylon. The study expands the chromosomal mapping data of repetitive sequences in wasps and offers insights into the dynamic evolutionary landscape of karyotypes in these insects.