Micro-evolution in grasshoppers mediated by polymorphic Robertsonian translocations

COLOMBO, P.C.

JOURNAL OF INSECT SCIENCE

UNIV ARIZONA

Lugar: Arizona; Año: 2013 vol. 13 p. 43 - 65

1536-2442

This review focus on grasshoppers which are polymorphic for Robertsonian translocations, because in these organisms the clarity of meiotic figures allow the study of chiasma distribution, and the orientation of trivalents and multiples in metaphase I. Only such five species of grasshoppers were found in the literature, all of them from the New World: 1. Oedaleonotus enigma; 2. Leptysma argentina; 3. Dichroplus pratensis; 4. Sinipta dalmani and 5. Cornops aquaticum. A general feature of most cases (except O. enigma) is that fusion carriers suffer a marked reduction of proximal and interstitial (with respect to the centromere) chiasma frequency; this fact, along with the reduction in the number of linkage groups with the consequent loss of independent segregation, produces a marked decrease of recombination in fusion carriers. This reduction in recombination has led to the conclusion that Robertsonian polymorphic grasshopper species share some properties with inversion polymorphic species of Drosophila, such as the central- marginal pattern (marginal populations are monomorphic, central populations being highly polymorphic). This may be the case of Dichroplus pratensis, which is certainly the most complex Robertsonian polymorphism system here studied. However, L. argentina and C. aquaticum do not display this pattern. This issue is open to further research. Since C. aquaticum is soon to be released in South Africa as a biological control, the latitudinal pattern found in South America may repeat there. This is an ?experiment? whose outcome may be have interesting developments in the near future.