title: Patterns of rDNA chromosomal localization in Palearctic Cephalota and Cylindera (Coleoptera: Carabidae: Cicindelini) with different numbers of X-chromosomes.
abstract: The ribosomal clusters of six Paleartic taxa belonging to the tiger beetle genera Cephalota Dokhtourow, 1883and Cylindera Westwood, 1831, with multiple sex chromosomes (XXY, XXXY and XXXXY) have been localised on mitotic and meiotic cells by fluorescence in situ hybridization (FISH), using a PCR-amplified 18S rDNA fragment as a probe. Four patterns of rDNA localization in these tiger beetles were found: 1. Two clusters located in one autosomal pair; 2. Two clusters located in one autosomal pair and one in an X chromosome; 3. Three clusters located in three heterosomes (XXY); 4. Two clusters located in one autosomal pair and two in the heterosomes (one of the Xs and the Y). These results illustrate that ribosomal cistrons have changed their number and localization during the evolution of these genera, showing a dynamic rather than a conservative pattern. These changes in rDNA localization are uncoupled with changes in the number of autosomes and/or heterosomes. A mechanism that involves transposable elements that carry ribosomal cistrons appears to be the most plausible explanation for these dynamics that involve jumping from one location in the genome to another, in some cases leaving copies in the original location.
authors.affiliation: Centro de Biologia Ambiental/Departamento de Biologia Animal/, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, Bloco C2 - 3º Piso, 1700 Lisboa, Portugal.
authors.forename: Sonia
authors.initials: S
authors.lastname: J R Proença
authors.forename: Artur
authors.initials: A
authors.lastname: R M Serrano
authors.forename: José
authors.initials: J
authors.lastname: Serrano
authors.forename: José
authors.initials: J
authors.lastname: Galián
keywords: Cephalota; Cicindelini; Coleoptera; Cylindera; FISH; chromosome evolution; ribosomal genes