RESUMEN
As in most Hymenoptera, the eusocial stingless bees (Meliponini) have a complementary sex determination (CSD) system. When a queen makes a "matched mating" with a male that shares a CSD allele with her, half of their diploid offspring are diploid males rather than females. Matched mating imposes a cost, since diploid male production reduces the colony workforce. Hence, adaptations preventing the occurrence or attenuating its effects are likely to arise. Here we provide clear evidence that in the stingless bee Scaptotrigona depilis, the emergence of diploid males induces queen death, and this usually occurs within 10-20 days of the emergence of diploid male offspring from their pupae. Queens that have not made a matched mating die when introduced into a colony in which diploid males are emerging. This shows that the adult diploid males, and not the queen that has made a matched mating herself, are the proximate cause of queen death. Analysis of the cuticular hydrocarbon profiles of adult haploid and diploid males shows six compounds with significant differences. Moreover, the diploid and haploid males only acquire distinct cuticular hydrocarbon profiles 10 days after emergence. Our data shows that the timing of queen death occurs when the cuticular hydrocarbons of haploid and diploid males differ significantly, suggesting that these chemical differences could be used as cues or signals to trigger queen death.
Asunto(s)
Abejas/genética , Abejas/fisiología , Diploidia , Conducta Sexual Animal , Animales , Abejas/química , Abejas/metabolismo , ADN/análisis , Femenino , Hidrocarburos/química , Hidrocarburos/metabolismo , Larva/química , Larva/metabolismo , Larva/fisiología , Masculino , ReproducciónRESUMEN
Aphid species can be polyphagous, feeding on multiple host plants across genera. As host plant species can have large variation in their phloem composition, this can affect aphid fitness and honeydew composition. Previous research showed significant intraspecific genotype variation in the composition of the honeydew carbohydrates of the black bean aphid Aphis fabae, with the ant attractant trisaccharide melezitose showing especially large variation across different genotypes. In this study, we test if variation in melezitose and carbohydrate composition of aphid honeydew could be linked to the adaptation of specific aphid genotypes to particular host plants. To this end, 4 high and 5 low melezitose secreting genotypes of the black bean aphid Aphis fabae were reared on 4 common host plants: broad bean, goosefoot, beet, and poppy. The carbohydrate composition, and in particular melezitose secretion, showed important aphid genotype and host plant interactions, with some genotypes being high melezitose secreting on 1 host plant but not on another. However, the interaction effects were not paralleled in the fitness measurements, even though there were significant differences in the average fitness across the different host plants. On the whole, this study demonstrates that aphid honeydew composition is influenced by complex herbivore-plant interactions. We discuss the relevance of these findings in the context of ant-aphid mutualisms and adaptive specialization in aphids.