Storage protein content as a functional marker for colony-founding strategies:: A comparative study within the harvester ant genus Pogonomyrmex

Claustral colony founding, in which new queens rear their first clutch of workers solely from internal reserves, is common in the higher ant subfamilies and is believed to represent a major innovation in ant life histories. The ability to store large amounts of amino acids contained in storage proteins is an essential physiological trait for claustral colony founding by ant queens. To determine whether there is an association between storage protein content and colony-founding strategy, we identified and quantified two major storage proteins in queens of five harvester ant species in the genus Pogonomyrmex that differ in colony-founding strategy. Queens of the fully claustral nonforaging species Pogonomyrmex rugosus and Pogonomyrmex maricopa contained the greatest amount of these proteins. Facultatively foraging semiclaustral Pogonomyrmex occidentalis queens contained an intermediate amount. Obligately foraging semiclaustral Pogonomyrmex californicus queens from two different populations contained significantly less storage protein than the other independent-founding species. Queens of the dependent-founding social parasite Pogonomyrmex anergismus also contained little storage protein. Our results suggest that storage protein content has evolved in concert with colony-founding strategies in the genus Pogonomyrme and provides a good functional marker for colony-founding strategy.