ALLOMETRIC AND MULTIVARIATE-ANALYSIS OF SEX AND CASTE POLYMORPHISM IN THE NEOTROPICAL STINGLESS BEE, SCAPTOTRIGONA-POSTICA

Morphometric data obtained from natural and in vitro-reared queens, workers, and drones of the stingless bee. Scaptotrigona postica were subjected to allometric and multivariate tests to study sex- and caste-related growth patterns. As imaginal phenotype variation appears to be restricted in members of a normal colony, the inclusion of in vitro-reared individuals permitted an analysis of a considerably wider size range for each morph. and proved important for the calculation of reliable regression statistics in the allometric analyses. Our results show that essentially no individuals with a mixture or transition of sex or caste traits are produced, and, consequently, that for most morphometric characters, queens, workers, and drones lie on different regression lines. Hence, workers cannot be considered as masculinized females, as has been suggested in studies based exclusively on multivariate analyses. Instead, the various morphs may result from a stepwise programming and reprogramming of a few growth rule parameters during critical stages of preimaginal development, and complex hypothetical shifts in the balance of maleness and femaleness genes need not be assumed. A multivariate discriminant analysis, on the other hand, proved to be an efficient tool for the selection of diagnostic size characters.