Is rapid evolution common in introduced plant species?

What is it about?

We used over 1900 herbarium specimens to determine whether morphological traits [plant height, leaf mass per area (LMA), leaf area or leaf shape] have shown significant change during the last ∼150 years in 23 plant species introduced to New South Wales, Australia. Seventy per cent of our study species showed a change in at least one trait through time. The most common change was in plant height (eight out of 21 species). Six of these showed a decrease in height through time. Decreases in height mainly occurred in western New South Wales where dry, low nutrient conditions may favour shorter plants. We also found changes in leaf traits, including one decrease in LMA, five changes in leaf shape, and three changes in leaf area. The magnitude of these changes was surprisingly large, up to 125% increase over 100 years. Control species showed significantly fewer changes than the introduced species. The majority of our study species showed morphological change through time. While common garden experiments will be required to rule out phenotypic plasticity as an alternative explanation for these patterns, our results suggest that rapid evolution in introduced plant species could be much more common, and of a much greater magnitude than previously thought.

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Why is it important?

Evolution is commonly thought to be a slow gradual process. Our results indicate that morphological changes (most likley due to evolution) can occur rapidly in species introduced into a new environment.