Evolutionary implications of early male and satellite nest production in Polistes exclamans colony cycles

Abstract

1. Polistes exclamans populations in central Texas have a unique colony cycle. Of all P. exclamans nests 20%–38% produce males with the first brood of workers. Nests producing early males have significantly more females, cells, pupae, and emergences at the time of early male production than nests not producing early males. 2. Early male production may have originated as an adaptation caused by the large number of queens that die before autumn reproductive males and females are produced. It allows egg laying by workers with whom early males mate. 3. Queens or workers sometimes leave their original nest and start new nests nearby that must be joined by workers from the original nest if they are to succeed. Such ‘satellite nests’ were initiated from May to July by 16%–39% of all nests, depending on the population. Although nests initiating satellites have significantly more females and pupae than nests not initiating satellites, satellite nest production by a given nest is not dependent on prior early male production, and is independent of the number of foundresses. 4. More P. exclamans nests 1976–1979 were lost to birds than to any other cause. In the period 1976–1979, 66.7% of the 12 nests with satellites succeeded in producing reproductives after being knocked down while only 5.7% of the 87 nests without satellites that were knocked down were subsequently successful. Concealed nests are less vulnerable to bird predation. 5. The brood parasitoid, C. iphitalis, a pyralid moth, avoids previously infested nests, therefore satellite nesting does not reduce the impact of this parasitoid. However, the brood parasitoid E. polistis, a chalcid wasp, lays eggs in the nest it emerges from, hence a satellite nest provides an escape when this parasitoid is already in the main nest.