Positive Allometry of Horns in the Rhinoceros Beetle Golofa xiximeca Does Not Follow Breaking-Point Patterns

Scaling relationships between horns and body size were analyzed for a population of male rhinoceros beetle Golofa xiximeca Moron. Recent accounts suggested that horns of several species of most of the genera in the rhinoceros beetle subfamily Dynastinae showed positive and breaking-point allometries. To learn if the pattern was the same in G. xiximeca, we used allometric analysis to search for linear and breaking-point allometries of 46 males. The results suggested that patterns of the head horn and the pronotal horn were linear. The scale of the pronotal horn and head horn was significantly positively correlated with body size. The analysis indicated steeper slope with 5.20 units for the pronotal horn than the head horn slope with 4.33 units, but comparison analysis showed differences in slope were not statistically significant. Results were discussed in the context of sole versus mixed data collection and positive allometric response to selection pressure.