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'Rule breaking' plants may be climate change survivors

11 February 2020
Can invasive plants teach us about climate adaptation?
Plants that break some of the 'rules' of ecology by adapting in unconventional ways may have a higher chance of surviving climate change, according to new research.
Photo of a humble weed-like plant called Plantago on a cliff overlooking Irish coast

A plantain (Plantago lanceolata) growing in its native habitat, Ireland. Photo: Dr Annabel Smith

Plants that break some ecological rules by adapting to new environments in unconventional ways could have a higher chance of surviving the impacts of climate change, according to a new study from researchers at the University of Sydney, Trinity College Dublin and the University of Queensland.

Professor Glenda Wardle, from the University of Sydney’s Desert Ecology Research Group, is one of the founding members of the international PlantPopNet team that coordinated the global collaborative research.

“The study is exciting as it is the first publication from the PlantPopNet team,” she said. “We were able to attract researchers from around the world to study in their own backyard, at a low cost. It’s a humble plant but it has the right mix of interesting biology to be a model for how plants might respond to altered environments.”

Photo of Dr Annabel Smith in a field in Ireland

Lead author Dr Annabel Smith measures a Plantago during the annual census on Inis Oirr, Ireland.

Dr Annabel Smith, from UQ’s School of Agriculture and Food Sciences, Professor Yvonne Buckley, from both UQ’s School of Biological Sciences and Trinity College Dublin, Ireland, and PlantPopNet studied the humble plantain (Plantago lanceolata) in an attempt to see how it became one of the world’s most successfully distributed plant species.

“We hoped to find out how plants adapt to hotter, drier or more variable climates and whether there were factors that made them more likely to adapt or go extinct,” Dr Smith said. “The plantain, a small plant native to Europe, has spread wildly across the globe – we needed to know why it’s been so incredibly successful.”

photo of Professor Glenda Wardle

Professor Glenda Wardle

What makes Plantago special?

Professor Wardle said Plantago is a valuable pasture plant that provides food for butterflies and other wildlife. It is also used in herbal teas and herbal remedies by humans.

She said: “Understanding how plants contribute to ecosystems – farms, diversity along roadsides in the introduced range, and meadows in the native range – is more important as humans find more ways to live with nature, rather than remove it.”

photo of Plantago plant close up

"The ‘rules of ecology’ simply didn't apply to this species," said Dr Smith.

Breaking the rules

Led by Dr Annabel Smith, the team set up 53 monitoring sites in 21 countries, including multiple sites in Australia. They tagged individual plants, tracked plant deaths and new seedlings, counted flowers and seeds and looked at DNA to see how many individual plants have historically been introduced outside Europe.

What they discovered went against existing tenets of ecological science.

“We were a bit shocked to find that the ‘rules of ecology’ simply didn't apply to this species,” Dr Smith said.

“Ecologists use different theories to understand how nature works – developed and tested over decades with field research - these are the so-called ‘rules’.

One of these theories describes how genetic diversity or variation in genes embedded in DNA are produced by changes in population size.

Dr Smith said that this means small populations tend to have little genetic diversity, while large populations with many offspring, such as those with lots of seeds, have more genetic diversity.

“Genetic diversity sounds boring, but actually it's the raw material on which evolution acts; more genetic diversity means plants are better able to adapt to environmental changes, like climate change,” Dr Smith said.

“We discovered that, in their native range, the environment determined their levels of genetic diversity. But, in new environments, these rule breakers were adapting better than most other plants.”

Winning at evolution

The team found the plantain’s success was due to multiple introductions around the world, which forced genetic diversity throughout the wider species.

“The DNA analyses showed us that ongoing introductions into Australia, New Zealand, North America, Japan and South Africa quickly prompted genetic diversity in these ‘expats’, giving them a higher capacity for adaptation,” Dr Smith said.

“In Europe plantains played by the rules, but by breaking it outside of Europe, it didn't matter what kind of environment they were living in, the plantains almost always had high genetic diversity and high adaptability.”

Dr Smith said the finding was fascinating for two crucial reasons.

“It’s important we now know that multiple introductions will mix genetic stock and make invasive plants more successful quite quickly – an important finding given some invasive species cause extinction to native plants and cost governments billions of dollars,” she said.

“And secondly, research on invasive plants can give us clues about how our native plants might adapt to climate change. Knowing what might make our plants more adaptable, more quickly, is essential.”

Photo of Plantago from above

Plantago growing in Canberra. Photo: Dr Annabel Smith

Plantago facts

  1. wide distribution, native in Europe and introduced in Australia, New Zealand, North America
  2. well studied because of chemistry in leaves and interesting reproduction
  3. usually wind dispersed and also visited by insects
  4. common along roads and in lawns, but often over-looked
  5. important pasture plant
  6. used in herbal teas and herbal remedies
  7. host to vulnerable butterfly populations overseas
  8. kids play with the stems and ‘flick' the head of flowers away by twisting the stem

Declaration: Professor Glenda Wardle received partial funding from Australian Research Council for this project.

Elissa Blake

Assistant Media Adviser (Science)

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