Leptysma argentina, Bruner, 1906

Colombo, Pablo César & Remis, María Isabel, 2015, Morphometric variation in chromosomally polymorphic grasshoppers (Orthoptera: Acrididae) from South America: Bergmann and converse Bergmann patterns, Florida Entomologist 98 (2), pp. 570-570 : 570-

Leptysma argentina

Leptysma argentina bears a polymorphism for a Robertsonian translocation called “fusion 3/6” in most of its analyzed populations. In a low-ranging cytogeographical analysis covering latitudes 31°S to 34°S in mid-eastern Argentina, this rearrangement was observed to be correlated with latitude (frequency zero in the northernmost population and frequency one in the southernmost, with all the intermediate frequencies in between these latitudes) ( Table 3; Fig. 1B ). Moreover, in this species, body size-related variables were larger in fusion homozygotes than in unfused homozygotes; the effect over heterozygotes was variable ( Table 4). This trend is clear both in males ( Colombo 1989; 1997) and in females ( Colombo et al. 2001; 2004) all over the geographical gradient.

The correlation of fusion 3/6 frequency with body size-related variables was stunning ( Colombo 1989; 1997), but it should be recognized that, superimposed on the fusion 3/6 effect, there was a within-karyo- type latitudinal effect ( Colombo 1997). It could be affirmed, with con- siderable care given the limited extent of the gradient (latitude 31°S to 34°S), that L. argentina showed a positive Bergmann’s effect (r = 0.9297, P = 0.0221) ( Fig. 1B ). Besides, it can be said that the polymorphic chromosome rearrangement, in this case more clearly than in T. pallidipennis , would have an adaptive effect, at least with respect to body size–related characters.

Figures

Fig. 1. A) Trimerotropis pallidipennis: Tegmen length (in mm) against altitude; B) Leptysma argentina: Total body length in mm against latitude; C) Cornops aquati- cum: Tegmen length in mm against latitude in males; and D) Cornops aquaticum: Tegmen length in mm against latitude in females.