Chromosomal variation, macroevolution and possible parapatric speciation in Mepraia spinolai (Porter) (Hemiptera: Reduviidae)

mepraia spinolai is an endemic species in chile that lives in wild and domestic habitats. it is the only species of the reduviidae family that shows alate polymorphism; females are always wingless, but males can be found with and without wings. the m. spinolai karyotype consists of 10 pairs of autosomes and a complex sex determination system. males from the northernmost regions i and ii (latitude 18°-26° south) are always winged (braquipterous) and are x1x2y, with a large y chromosome. from region iii to the metropolitan region (latitude 26°-33° south), males may be either winged or wingless but appear to be polymorphic for a small neo-y chromosome, which may have originated by fracture of the large holocentric y chromosome found in populations from farther north. experimental crosses suggest that the genes for wings are linked in the y chromosome and also that there are two cytologically indistinguishable types of neo-y chromosomes. one form (y1) bears a gene or genes for wings while the other (y2) lacks such genes. males that are x1x2y1, x1x2y1y1 and x1x2y1y2 are winged, while the absence of y1 (x1x2y2 and x1x2y2y2 ) results in a wingless male. these chromosomes and morphological changes are correlated with a shift of the southern population into more arid habitats of the interior in the metropolitan region and region iii.