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Discovery made on Aquilegia spurs 

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Aquilegias yield clue to pollination puzzle

6 December 2011

Aquilegia 'Florida'

New research has brought scientists closer to explaining a conundrum dating back to Darwin's day: the puzzle of how flowers adapt their own structures to match the needs of different pollinators.

Researchers from Harvard University and the University of California, Santa Barbara, looked at different species of Aquilegia to explore how they grow spurs of different lengths to suit specific pollinating insects. Bees, for example, prefer the short spurs of A. vulgaris, but hawkmoths, with tongues measuring up to 22cm (9in) long, go for the long, graceful spurs of A. longissima.

The team found the differences in spur length on Aquilegia were decided during one simple change while the flower is developing, which results in elongated cells.

Previously it had been assumed that the great diversity of the Aquilegia genus was due to cell proliferation, but in fact the research team found 99% of the variation in cell length was attributed to the plant's ability to change round cells into long ones. They discovered all Aquilegia look the same until the spur is about 5mm (1/4in) long; after this cells elongate to varying extents, creating different cell lengths according to species.

The phenomenon of co-evolution was first observed by Charles Darwin, who speculated that the extremely long nectar spur on the Madagascan orchid Angraecum sesquipedale must have evolved to accommodate the equally long tongue of its pollinator – only 21 years later discovered to be an African hawk moth, Xanthopan morganii praedicta.

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