Charles Darwin used to love to putter about in his garden pondering the mysteries of life and after studying the foxgloves growing there concluded in 1878 that only bumblebees were capable of pollinating them. I'm sure that the news of a new study showing that, after being transplanted to the tropics in America, foxgloves have apparently evolved there to accommodate hummingbirds, would have elated him.
The researchers compared foxgloves being grown in Britain with those introduced to Costa Rica and Colombia approximately 200 years ago and have revealed how flowering plants can respond to a new environment -- as well as the presence of a new pollinator -- with some rapid physical changes.
The study discovered that the base of the narrow cone structure of the flowers, the proximal corolla tube (which hold the flower's nectar, which, due to the shape of the tube, is only accessible to pollinators with long mouth parts) was up to over a quarter times larger in foxgloves now growing in Colombia and Costa Rica.
The study's co-author, Maria Clara Castellanos of the University of Sussex said, "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."
The researchers made clear that while the changes observed in foxgloves are consistent with changes that hummingbirds have imposed on the native plants they pollinate, the study does not prove that the birds directly caused the rapid changes seen in the flowers, instead they emphasized the importance of studying other plants in this context.
As Castellanos remarked, "Plants around the world are experiencing changes in their pollinators and it is important to understand the evolutionary implications of this."
This all reminds me in a way of how apple maggot flies evolved through sympatric speciation from flies that had only laid their eggs only on hawthorns some 200 years ago after apples were introduced to America by immigrants roughly 200 years ago.
The full paper, Rapid evolution of a floral trait following acquisition of novel pollinators is available at the hyperlink provided. Here is the abstract:
The researchers compared foxgloves being grown in Britain with those introduced to Costa Rica and Colombia approximately 200 years ago and have revealed how flowering plants can respond to a new environment -- as well as the presence of a new pollinator -- with some rapid physical changes.
The study discovered that the base of the narrow cone structure of the flowers, the proximal corolla tube (which hold the flower's nectar, which, due to the shape of the tube, is only accessible to pollinators with long mouth parts) was up to over a quarter times larger in foxgloves now growing in Colombia and Costa Rica.
The study's co-author, Maria Clara Castellanos of the University of Sussex said, "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."
The researchers made clear that while the changes observed in foxgloves are consistent with changes that hummingbirds have imposed on the native plants they pollinate, the study does not prove that the birds directly caused the rapid changes seen in the flowers, instead they emphasized the importance of studying other plants in this context.
As Castellanos remarked, "Plants around the world are experiencing changes in their pollinators and it is important to understand the evolutionary implications of this."
This all reminds me in a way of how apple maggot flies evolved through sympatric speciation from flies that had only laid their eggs only on hawthorns some 200 years ago after apples were introduced to America by immigrants roughly 200 years ago.
The full paper, Rapid evolution of a floral trait following acquisition of novel pollinators is available at the hyperlink provided. Here is the abstract:
Abstract:
- Changes in the pollinator assemblage visiting a plant can have consequences for reproductive success and floral evolution. We studied a recent plant trans‐continental range expansion to test whether the acquisition of new pollinator functional groups can lead to rapid adaptive evolution of flowers.
- In Digitalis purpurea, we compared flower visitors, floral traits and natural selection between native European populations and those in two Neotropical regions, naturalised after independent introductions. Bumblebees are the main pollinators in native populations while both bumblebees and hummingbirds are important visitors in the new range. We confirmed that the birds are effective pollinators and deposit more pollen grains on stigmas than bumblebees.
- We found convergent changes in the two new regions towards larger proximal corolla tubes, a floral trait that restricts access to nectar to visitors with long mouthparts. There was a strong positive linear selection for this trait in the introduced populations, particularly on the length of the proximal corolla tube, consistent with the addition of hummingbirds as pollinators.
- Synthesis. The addition of new pollinators is likely to happen often as humans influence the ranges of plants and pollinators but it is also a common feature in the long‐term evolution of the angiosperms. We show how novel selection followed by very rapid evolutionary change can be an important force behind the extraordinary diversity of flowers.
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