SA bees’ adaptation amazes scientists
Legs have evolved to reach oil in snapdragons – research
NEW research from Stellenbosch University shows that, in an extraordinary case of adaptation, the disproportionately long front legs of South Africa’s oil-collecting Rediviva bee species have evolved in response to the equally long oil-producing spurs of snapdragons.
“This is one of the few examples where a pollinator had to adapt to the flowers it pollinates, rather than the other way round,” said Professor Anton Pauw, lead author of the article “Long-legged bees make adaptive leaps: linking adaptation to co-evolution in a plant- pollinator network”, published in the Proceedings of the Royal Society B: Biology.
Pauw, an evolutionary ecologist at the university, said pollinators often hold the key to understanding the genesis of floral diversity.
In other words, flowers have adapted to their pollinators in spectacular ways to be able to reproduce.
In this case, however, the little-known Rediviva bee species has developed front legs of varying lengths – from 6.923.4mm long – to reach the oil produced deep at the back of the snapdragon’s twin spurs. The length of these spurs also varies from species to species, with 70 species in the largest genus of oil-producing flowers, Diascia.
The bees’ front legs are coated in dense velvety hairs that soak up the oil, which is mixed with pollen to form a super-nutritious bread for the larvae in their underground nests. The oil is also used to line the walls of the nests.
Working in collaboration with researchers from Ger- many, the UK, Belgium and the US, Pauw used DNA analysis to produce a family tree for 19 of the 26 Rediviva species.
“We were able to show that very closely related bee species often differ dramatically in leg length and that this divergence could be explained by differences in the spur length of the flowers they visit.”
Documenting the network of interactions between the oil-collecting bees and the 96 plant species from which they gather oil, required many years of observation. Many of the oil-secreting plants flower only in the first year after a fire.
Pauw said the next step would be a phylogenetic analysis of snapdragons to test whether flower spur length and bee leg length evolved simultaneously as one would expect if bees and plants were co- evolving: “In this scenario, plants and bees evolve together in a sort of evolutionary dance.”
He said it was important, from an ecological perspective, to understand these interactions: “Oil-collecting bees are threatened by man’s activities, in particular by urbanisation. By understanding their role in generating and maintaining plant diversity, it might be possible to predict and ameliorate human impacts.”
Belinda Kahnt, Michael Kuhlmann, Denis Michez, Graham A Montgomery, Elizabeth Murray and Bryan N Danforth contributed to this article.
A female of the oil-collecting bee species Rediviva longimanus, which have disproportionately long legs, collects pollen.