Babiana ringens with the typical naked "rat tail" (Image: Spencer Barrett / Nature)
Reading To improve their chances of reproduction, South African iris plants offer a special service for birds: they grow a stable perch, from which the animals can easily reach the nectar in the calyx. This pole is so cleverly placed that the birds have to bend over the stamens of the flowers and the pollen sticks to their breasts. In this way, the tuberculoses achieve a significantly higher proportion of cross-pollination than without the bird's nest, a Canadian-South African research team has now been able to show. It is no coincidence that the iris plant with the scientific name Babiana ringens in the English-speaking world is also called "rat tail": The most striking feature of the plant is a naked, thick shoot that rises steeply and actually resembles a rat's tail. This shoot apparently has no other function than serving birds as a perch, researchers had previously suspected. From this position, the animals can easily reach the sweet nectar of the upturned flowers growing near the ground with their beaks. This is exactly what the rat tail plant wants to achieve: as it does not let its pollen be distributed by insects, but mainly by malachite nectar birds, luring the animals is essential for their reproductive success.

And this strategy really works, researchers discovered. They removed the extra shoot from some rat tail plants and observed how many visits from nectar birds got these plants compared to their intact conspecifics. The birds clearly preferred the plants with landing place, showed the evaluation. This also had significant consequences for the fertility of the plants: The female specimens without additional drive produced 47 percent fewer seeds than the original variant, and the researchers found a much higher proportion of self-fertilization.

The rat-tailed branch thus helps the plants to increase the proportion of cross-pollination and thus to mix their own genes with those of other specimens, the researchers conclude. Especially for the male birds, the additional drive seems to be a much more pleasant landing pad than the ground? probably because their long tail feathers make it difficult to start from the sandy bottom.

Bruce Anderson (University of KwaZulu-Natal, Pietermaritzburg) et al .: Nature, Vol. 435, p. 42 Indication

ddp / science.de? Ilka Lehnen-Beyel

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