Alternative Nesting Strategies of Polistine Wasps in a Subtropical Locale.

Abstract

Simple SummaryPaper wasps are eusocial insects which serve as excellent models for studying the evolution of sociality. In this study we provide a new and unique view of the nesting biology of social wasps by comparing and contrasting the phenology of species in two genera, Polistes and Mischocyttarus, in a context that sheds light on the life history and evolution of this group. Over the course of one year in subtropical Baton Rouge, USA, we found two nesting strategies, with Polistes having a second nesting cycle characterized by an abbreviated colony duration and smaller nests, and Mischocyttarus mexicanus having one nesting cycle characterized by long colony duration and few late season nests. Our results highlight phenological differences in the life history of an assemblage of social wasps in a subtropical locale, and support previous foundational works concerning the ancestral origins of the Polistinae.Phylogenetic studies suggest that historically all paper wasps (Vespidae: Polistinae) in North America have tropical origins, but some species have adapted to survive temperate conditions. Subtropical climates, which are intermediate between temperate and tropical, allow a unique opportunity to study ancestral traits which can be retained or lost within populations, and ultimately elucidate the process of social wasp evolution. We investigated the phenology of paper wasps at study sites in subtropical Baton Rouge, USA, through nest searching and monitoring of nest parameters throughout the warm season (March–October). Across the year, two periods of nest initiation occurred: from March–May (early season nests, i.e., before the summer solstice), and from July–September (late season nests, after the solstice). We observed 240 Polistes nests from six species, of which 50.8% were initiated in early season and 49.2% in late season. In contrast, Mischocyttarus mexicanus rarely built late season nests and had longer early season colony duration than Polistes bellicosus and P. dorsalis, which built more nests in the late season than early. Across all species, late season nests had significantly shorter colony duration (~87.6 days) than early season nests (~166 days), and only P. bellicosus had fewer adults at peak population in late season nests than in early season nests. Results indicate both a bivoltine colony cycle in Polistes of subtropical climates, as well as differences in nesting strategies between genera.