Neo-sex chromosomes in the Masculipennis species group (Dichroplus: Acrididae, Melanoplinae) : the cases of D. masculipennis and D. vittigerum

Abstract

Los saltamontes de melanoplina de América del Sur muestran un número desproporcionado de cariotipos derivados, incluyendo muchos casos de sistemas cromosómicos neo-sexuales. Esto es especialmente cierto para el género Dichroplus y su grupo de especies Maculipennis. Se analizaron los cromosomas cariotipo y neo-sexual en mitosis y meiosis de Dichroplus maculipennis y D. vittigerum de Argentina utilizando protocolos citogenéticos convencionales y fluorescentes con el fin de dilucidar el comportamiento y origen de estos sistemas neo-XY en relación con la filogenia actual de este grupo.

South American melanopline grasshoppers display a disproportionate number of derived karyotypes, including many cases of neo-sex chromosome systems. This is especially true of the genus Dichroplus and its Maculipennis species group. We analyzed the karyotype and neo-sex chromosomes in mitosis and meiosis of Dichroplus maculipennis and D. vittigerum from Argentina using conventional and fluorescent cytogenetic protocols in order to elucidate the behavior and origin of these neo-XY systems in relation to the current phylogeny of this group. Our results showed that D. maculipennis (2n = 22♂/22♀; neoXY/neoXX) and D. vittigerum, whose karyotype is described here for the first time (2n = 18♂/18♀; neoXY/neoXX), show highly evolved neo-XY systems, although with significant differences between them. Furthermore, both species differ for two autosomal fixed Robertsonian fusions present in D. vittigerum. Analysis of karyotypic character state optimization strongly suggests the independent origin and evolution of neo-sex systems within this species group.