Hard evidence was provided by the discovery by Hunt, Norberg, Wolschin, Amdam and co-workers of differing hexamerin storage protein levels in Polistes larvae and pupae destined to become workers or gynes. In combination with a prolonged developmental time in gynes, this finding indicates that differential provisioning of the larvae, prior to pupation, serves to promote a caste bias in which a higher level of nourishment results in primarily gyne-destined female wasps. According to Amdam, the developmental program of diapause, that also typifies solitary insects without castes, was adopted by evolution to produce Polistes females that look the same but differ in their potential to attain two distinct social roles. This adoption, the PNAS paper poses, provides the foundation for a major developmental switch: the divergence of workers and potentially reproductive gyne castes in some social hymenoptera.
The significance of their research in Polistes is two fold, according to the authors, it challenges the view that workers and gynes represent behavior options equally available to every female offspring, and it exemplifies how social insect castes can evolve from casteless lineages.
Amdam and her colleagues believe this research brings scientists one step closer to understanding how developmental programs in solitary insects can be remodeled to yield complex, social orders marked by castes and task specialization.
This isnt the first system in which Amdam has r
|Contact: Margaret Coulombe|
Arizona State University