Interaction among different heterocromatic variants in the grasshopper Dichroplus elongatus

Abstract

Simultaneous chromosome polymorphisms for supernumerary elements allow us to analyse the relationships among different forms of heterochromatic variation in nature. We report simultaneous variation patterns for supernumerary segments in chromosomes S10 (SS10), S9 (SS9) and S6 (SS6) and B chromosomes in nine populations of the grasshopper Dichroplus elongatus from two biogeographic provinces from east Argentina. Our results show spatial chromosome differentiation for three out of four supernumerary heterochromatic variants (B chromosomes, SS6 and SS10). The incidence of B chromosomes was negatively correlated with the SS10 frequency. The distribution pattern analysis shows different degree of differentiation among populations for each supernumerary heterochromatic variant suggesting that the detected chromosome variation cannot be explained by interaction between migration and genetic drift. Moreover, the observed population chromosome differentiation was not in agreement with the hierarchical analysis of molecular of heterogeneity at mitochondrial DNA level (mtDNA). The present results point out the importance of the interaction among heterochromatic variants in the chromosome intraspecific variation in east Argentina natural populations of the grasshopper D. elongatus.

C-banding characterization of centric fusion and heterochromatin polymorphisms in the water-hyacinth grasshopper, Cornops aquaticum (Orthoptera: Acrididae)

“…Some variants of supernumerary heterochromatin are polymorphic, and they are integrated into the genome as C-bands (Vosa 1976, Porter and Rayburn 1990), knobs (Longley 1938, González et al 2013, 2021), or supernumerary segments (SS) (Hewitt 1979, John 1983). Polymorphic supernumerary segments have been most extensively studied in orthopteroid insects (John 1973, White 1973, Schroeter and Hewitt 1974, Hewitt 1979, John 1981, Camacho et al 1984, John et al 1985, Cabrero et al 1986, Gosalvez et al 1987, Rodríguez Iñigo et al 1993, Remis 1989, Suja et al 1994, Remis et al 1998, 2004). Though SS can exhibit different response to C-banding (Perfectti et al 2000), most of them are C-positive so C- banding studies provide the opportunity to detect these.…”