American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Queen execution, diploid males, and selection for and against polyandry in the Brazilian stingless bee Scaptotrigona depilis

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Ayrton Vollet-Neto, Vera L. Imperatriz-Fonseca, and Francis L. W. Ratnieks (Nov 2019)

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<i>Scaptotrigona depilis</i> queen inspecting a brood cell. <br />(Credit: Ayrton Vollet-Neto)
Scaptotrigona depilis queen inspecting a brood cell.
(Credit: Ayrton Vollet-Neto)

Abstract

Female mating frequency varies. Determining the causes of this variation is an active research area. We tested the hypothesis that in stingless bees, Meliponini, single mating is due to the execution of queens that make a matched mating at the CSD (complementary sex determination) locus and have diploid male offspring. We studied the Brazilian species Scaptotrigona depilis. We made up 70 test colonies so that 50% (single matched mating), 25% (double mating), 12.5% (4-mating), or 0% (single non-matched mating) emerging brood were diploid males. Queen execution following diploid male emergence was equal and high in colonies producing 50% (77% executed) and 25% (75%) diploid males, versus equal and low in colonies producing 12.5% (7%) and 0% (0%) diploid males. These results show that queens that mate with two males with similar paternity suffer an increased chance of being executed, which selects against double mating. However, double mating with unequal paternity (e.g., 25:75), which occasionally occurs in S. depilis, is selectively neutral. Single mating and double mating with unequal paternity form one adaptive peak. The results show a second adaptive peak at 4-mating. However, this is inaccessible via gradual evolutionary change in a selective landscape with reduced fitness at double mating.