About queen production and selection in different stages of colony cycle in Epiponini (Vespidae:Polistinae).

Author(s)

Laura Elena Chavarría Pizarro

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto (PCARP/BC)
• Defense date: 2013-08-30

Examining board members

Fernando Barbosa Noll; Gisele Garcia Azevedo; Michael Hrncir; Sidnei Mateus; Sulene Noriko Shima

• Advisor: Fernando Barbosa Noll

Abstract

Epiponini wasps have colonies with multiple queens, which alternate their number under different stages of the colony cycle. Initially there are several potential queens, but as the colony cycle develops, queen number is reduced. Because most of individuals remain reproductively totipotent there is great potential for conflicts over reproduction. Under this conditions workers could have an advantage to control queen production because they are the dominant caste. Reproductive control could be performed by chemical signals, which along with ritualized behaviors communicate queen presence in the colony. However, queen selection process is a little known across Epiponini, and for this reason our goal was to study queens and workers behavior during queen selection phase, performing a phylogenetic analysis to understand behavioral changes among species. We performed observations in nine species belong to five genera: Chartergellus, Metapolybia, Protopolybia, Polybia, Brachygastra. We marked queens, a sample of workers and newly emerged females to perform direct and video focal observations. To induce queen production, we performed queen removal tests. Some of queens characteristic behaviors and those associated with queen selection process were analyzed via phylogenetic optimization. Bending display I (BD1) is a dominance display performed queens against workers, is the behavior that better identify queens and is also basal for all Epiponini clades. BD1 perform from workers to queens is an apomorphy of Metapolybia. Another test behaviors performed among queens appeared independently in some species, and could be related with an increase of interaction complexity. Worker tests were present in the Epiponini ancestor, indicating that workers are in charge of queen control. Worker dance behavior was synapomorphic for the clade composed by Polybia, Metapolybia and their close related genera, in which workers test queens reproductive potential. Apparently, ritualized tests and dominance behaviors are used in Epiponini as honest signals of queens reproductive potential instead of aggressive behaviors. In Metapolybia and in Protopolybia exigua, BD1 is performed with high frequency after queen elimination and during queen selection process. On the other hand, in Chartergellus and Protopolybia picteti displays frequency did not change. In Chartergellus BD1 frequency did not change because females do not interact to each other a lot, also queen selection is performed by queens expulsion instead by tests. In P. picteti we possibly failed to remove all queens from the colony. Metapolybia and Chartergellus have reproductive tolerance between females during first stages of colony cycle, and queen elimination induced females to lay eggs, but queen number eventually is reduced. These results suggest that reproductive control in fact could be performed by chemical signals. On the other hand, in Protopolybia queens number change little during the colony cycle. In adition, intermediates constantly attempt to lay eggs. Persistence oviposition could be convenient for intermediates in Protopolybia to achieve queen status in new colonies. Females totipotency to develop ovaries is also basal for Epiponini. Not only young females develop their ovaries under queen lost; old and middle age individuals also attempt to replace the queen. Caste flexibility is decisive for colony survival of swarm wasps because allows colonies to respond efficiently to different situations that may eventually arise. (AU)

• FAPESP's process: 09/07526-2 - On the selection and production of queens in different stages of the colony cycle in the Epiponini (Vespidae: Polistinae)
• Grantee: Laura Elena Chavarría Pizarro
• Support Opportunities: Scholarships in Brazil - Doctorate