Chromosome evolution in South American Melanoplinae (Orthoptera: Acrididae)

CASTILLO ELIO R.D

Congreso; XXXIII CONGRESO BRASILEIRO DE ZOOLOGIA; 2018

Acridid grasshoppers display an apparent karyotypic stability, with the vast majority of species exhibiting a standard acro-telocentric karyotype (2n=23♂/24♀; FN=23/24) and X0/XX sex chromosome determination mechanism (SCDS). Nevertheless, evolutionary structural modifications of the standard karyotype due to different types of chromosomal mutations have occurred along their history. One of the most important components of chromosome variation in Acrididae is constituted by neo-sex chromosome determination systems (neo-SCDS), which arose from standard X0/XX systems within several lineages. South American Melanoplinae received special attention in this aspect. The Scotussae group of genera include several clades showing species with extensive variation in the chromosome number, morphology and derived neo-SCDS (i.e. Ronderosia, Atrachelacris, Dichromatos, Eurotettix, Scotussa, Leiotettix, Chlorus). The observed neo-SCDS diversity is explained by the occurrence of chromosomal rearrangements, the most recurrent being a centric fusion between the X chromosome and an autosome, the neo-X, the non-fused autosome partner becoming the neo-Y. Dichroplus is another striking group studied in this aspect with species showing different evolutionary examples of neo-sex chromosome. This genus is also special not only because derived sex chromosomes evolve through additional chromosomal rearrangements but also comprises representatives considered major pests of several crops (barley, rye, oats, wheat, flax, lucerne) and forages on natural pastures in Argentina (i.e. D. maculipennis, D. elongatus, D. vittatus). The cytogenetic information supports the hypothesis that substitution from X0/XX to a derived neo-SCDS were favored during the evolutionary history of neotropical Melanoplinae. However, the understanding of the mechanisms that rule sex determination in South American Melanoplinae (Orthoptera) is still a challenge. An interesting contribution could be the analysis of all these karyotypic information in a phylogenetic context, which is fragmented in this group.@font-face { font-family: "Times New Roman";}@font-face { font-family: "宋体";}@font-face { font-family: "Calibri";}p.MsoNormal { line-height: 107%; font-family: Calibri; }span.msoIns { text-decoration: underline; color: blue; }span.msoDel { text-decoration: line-through; color: red; }div.Section0 { }