SA bees’ adap­ta­tion amazes sci­en­tists

Legs have evolved to reach oil in snap­drag­ons – re­search

Weekend Argus (Saturday Edition) - - FRONT PAGE - WEEK­END ARGUS RE­PORTER

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.

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