Tetragonula stingless bees are amazing for several reasons: some species look exactly the same but build completely different types of nest; they're important natural pollinators that are also sometimes reared (and transported) by small-scale beekeepers; and the workers are fully sterile, which means that this taxon represents an independent origin of the extreme form of social living that we call 'superorganismality'. In the paper, published in the Molecular Ecology journal, the research team tested a series of hypotheses about population genomics and social evolution in two species of Tetragonula that live in eastern Australia.
Benjamin Taylor and the research group generated the first genome for any species in this group, and used it to test the hypothesis that population barriers across these species are being broken down by human movement of hives for beekeeping. They found that there are strong genomic differences among Tetragonula populations, probably driven by natural arid gaps separating the eucalypt forests on which these bees rely. While some human movement of hives was genetically evidence, overall we found no evidence that meliponiculture (stingless beekeeping) is breaking down these population barriers.
Scientists also investigated the effects of sociality in these bees’ genomes. Full worker sterility is a very rare and important trait, and Tetragonula bees represent a completely independent origin, so they wanted to know if the genomic signatures in this lineage would be the same or different from those seen in other ‘superorganisms’ such as honey bees. Using a combination of genomic and gene expression analyses, the HFSP Awardee found that at a broad genomic level, Tetragonula shows many of the same signatures of social evolution found in other independent origins of worker sterility, including ‘worker genes’ that show biases in favour of high genetic diversity and fast rates of evolution. However, the specific genes that produce worker and queen phenotypes in stingless bees are actually quite different from those that perform the same role in honey bees. That means there are many different ways of becoming a superorganism, even if the ecological outcomes of those mechanisms ultimately converge.
This work is part of Benjamin Taylor's broader HFSP project, which investigates how multi-omic studies (those that combine multiple types of large-scale biological data) can help us understand the evolution of social living.