Annual cycle of nest composition in the queen‐dimorphic weaver antPolyrhachis australis Mayr, 1870 (Hymenoptera:Formicidae) in northernQueensland

Abstract

AbstractTheAustralian spiny weaver antPolyrhachis australis Mayr, 1870 is an arboreal formicine ant that constructs nests using silk and particulate matter (carton). BetweenSeptember 2009 andDecember 2012, the contents of 181P. australisnests were recorded. Of these, 14% were queenless, 21% were monogynous and 65% were polygynous. Monogynous nests had more than double the number of brood per queen, but were outnumbered nine to one by polygynous nests inJanuary, just after the reproductive phase and before the heaviest rain of the wet season. This proportion fell close to equal before the start of the next reproductive phase inSeptember, suggesting attrition of queens by competition during the ergonomic phase of the annual cycle that peaks inMay. The reproductive phase of the annual cycle started with the appearance of new gynes inSeptember throughNovember. Male production increased inOctober, peaked inNovember andDecember, and declined inJanuary. Hence, gynes were produced before males (protogyny). The pupal sex ratio was heavily male‐biased during this time. Males continued to be produced in relatively low numbers throughout the year, supporting (along with other evidence including nest‐size limiting habitat structure) the view thatP. australiscolonies are polygynous and polydomous. The polygynous status of most nests may have arisen more from retention of queens in the mother nest than from adoption. Queen size was bimodal and the microgyne–macrogyne dimorphism may point to a mixed strategy of nest/colony founding whereby macrogynes typically fly and establish colonies independently, while microgynes typically walk to new nest sites and found nests dependently under the protection of a retinue of workers. In support of this inference, all of 49 queens which displayed brachyptery or other wing malformations were microgynes.