Hummingbirds alter their food sources – evolution catalysts

As regular readers know, I have a thing for hummingbirds. I feed them, i photo them, i listen to their songs and i can watch them for hours. A recent scientific study suggests that hummingbirds also alter the evolution of their food sources so the plants change to better accomodate hummingbird feeding.

Quote: “Researchers have found common foxgloves brought to the Americas have rapidly evolved to change flower length in the presence of a new pollinator group, hummingbirds. The findings are published in the British Ecological Society’s┬áJournal of Ecology.”

The gist of the story is right here, quote:

The researchers compared foxgloves in the UK, which are pollinated by bumblebees, with foxgloves introduced in two independent events to Costa Rica and Colombia around 200 years ago, which are pollinated by different species of bumblebees and also hummingbirds. They found the base of the cone structure of the flowers, called the proximal corolla tube, was 13-26% larger in populations in the Americas.

Foxgloves have long, narrow proximal corolla tubes. This part of the flower holds the nectar and by being this shape, they restrict floral visitors to those with long mouthparts such as long-tongued bumblebees.

“We found foxglove populations in Costa Rica and Colombia now have flowers with longer tubes at the base, when compared to native populations. There is also substantial natural selection on this floral characteristic in the naturalised populations.” said Dr Maria Clara Castellanos at the University of Sussex and one of the authors of the study.

“Long corollas are a common feature in many hummingbird-pollinated plants, likely because this improves the precision of pollen transfer during the pollination interaction. It is also possible that long corolla tubes exclude other pollinators that are less effective.”

Because foxgloves are biennial (meaning each generation takes two years) these changes have occurred in around 85 generations, indicating a rapid evolutionary change.

In the study the researchers also confirmed that hummingbirds are effective foxglove pollinators. “We counted pollen grains deposited in flowers and found that after a single visit they can bring in more pollen than a bumblebee.” said Dr Castellanos.

The authors close the summary with the obvious question, though stated rather than asked, paraphrased into a question – what other evolutionary accelerations are occurring due to plants experiencing different pollinators?

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