Mys­tery of long-legged bees solved by sci­en­tists

The Herald (South Africa) - - NEWS - Dave Cham­bers

SCI­EN­TISTS have dis­cov­ered why a South African bee species have grown ex­traor­di­nar­ily long legs.

Re­search at Stel­len­bosch Univer­sity has found that oil-col­lect­ing Re­di­viva bees‚ first de­scribed in 1984‚ evolved legs of up to 23mm to har­vest oil from the equally long spurs of snap­dragon flow­ers.

“This is one of the few ex­am­ples where a pol­li­na­tor had to adapt to the flow­ers that it pol­li­nates‚ rather than the other way round‚” ecol­o­gist An­ton Pauw wrote in the peer-re­viewed Pro­ceed­ings of the Royal So­ci­ety B: Bi­ol­ogy.

Lead author Pauw‚ of the botany and zo­ol­ogy de­part­ment at Stel­len­bosch‚ said flow­ers of­ten adapted to their pol­li­na­tors in spec­tac­u­lar ways to be able to re­pro­duce.

In this case‚ how­ever‚ Re­di­viva bees had de­vel­oped front legs of vary­ing lengths – up to 23.4mm in the case of the “longi­manus” vari­ant – to reach oil at the back of the snap­dragon’s twin spurs.

Spur length also varies be­tween the 70 species in the largest genus of oil-pro­duc­ing flow­ers (Di­as­cia)‚ indige­nous to South Africa.

The bees’ front legs are coated in vel­vety hairs that soak up the oil‚ which is then mixed with pollen to form a su­per-nu­tri­tious bread for lar­vae in un­der­ground nests. The oil is also used to line nest walls.

Work­ing with re­searchers from Ger­many‚ the UK‚ Bel­gium and the US‚ Pauw an­a­lysed DNA of 19 of the 26 Re­di­viva species.

“We were able to show 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 that they visit‚” he said.

Doc­u­ment­ing in­ter­ac­tions be­tween oil-col­lect­ing bees and the 96 plant species re­quired years of ob­ser­va­tion.

The next step will be to an­a­lyse snap­drag­ons’ genes to test whether spur length and leg length evolved si­mul­ta­ne­ously.

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