New contributions to the cytotaxonomy of tiger beetles (Coleop-tera, Cicindelidae) from the Afrotropical Region: cytogenetic characterization of Prothyma concinna, Elliptica lugubris and Ropaloteres cinctus

Abstract

-Metaphases from germinal tissue of three Afrotropical species of tiger beetles occurring in Guinea-Bissau were analysed using conventional Giemsa-staining. The species showed distinct karyotypes and multiple and morphologically diverse sex chromosome systems: 2n = 20 + X 1 X 2 X 3 X 4 Y for Prothyma concinna, 2n = 18 + X 1 X 2 X 3 Y/X 1 X 1 X 2 X 2 X 3 X 3 for Elliptica lugubris and 2n = 22 + X 1 X 2 X 3 X 4 Y for Ropaloteres cinctus. The existence of a higher number of autosome pairs in P. concinna and R. cinctus (10 and 11 respectively) when compared with the stability of 9 autosome pairs in most species of genus Cicindela (s.l.) supports the hypothesis of a gradual reduction in the number of autosomes in the karyotype evolution of cicindelids. This reduction might have been achieved by centric fusions considering the almost general mediocentric morphology of autosomes and the existence of acrocentric chromosomes in some basal species of Cicindelini. The existence of one chromosome in P. concinna assigned to the sex system with strong blocks of heterochromatin in the short arm and in the distal region of the long arm could favour such an assumption and may question the hypothesis of a complete independent evolution for autosomes and heterosomes.