THE COMPLEX ROBERTSONIAN SYSTEM OF DICHROPLUS-PRATENSIS (MELANOPLINAE, ACRIDIDAE) .1. GEOGRAPHIC-DISTRIBUTION OF FUSION POLYMORPHISMS

A chromosomal survey was performed in Argentine natural populations of the South-American melanopline grasshopper Dichroplus pratensis Bruner (Acrididae). The cytogenetic study of samples from different populations revealed the existence of at least 7 distinct Robertsonian translocations which involve the 6 L (large) autosomes of the 2n = 20 (female)/19 (male) all-telocentric standard karyotype. Some of the fusions thus share monobrachial homologies. The Robertsonian variation found in D pratensis is discussed in relation to a model of chromosomal evolution for the species in which the changes in recombination patterns produced by the fusions are central.