This Carnivorous Plant Needs Its Home to Burn

Like the mythical Phoenix, the Portuguese Sundew is reborn from ashes, but that's a problem when people protect your habitat from flames.

Like much of Europe this year Drosophyllum lusitanicum, the Portuguese Sundew, is suffering from wildfires. However, it is the fire management that is making life difficult in the truest sense for this endangered carnivorous plant. Current conservation management practices try to control wildfire, as it poses a high threat to the rich biodiversity of Mediterranean heathlands. However, a new study published in ‘AoB PLANTS’ shows that Portugese Sundew seeds thrive best after being exposed to short bursts of high heat – as happens when a wildfire blazes across a heathland.

Drosophyllum lusitanicum, the Portuguese Sundew
Drosophyllum lusitanicum Photo: Fernando Ojeda

The research by an international team, led by Adam Cross of Curtin University in Western Australia, has been looking into what Portuguese sundew seeds need to germinate, in an effort to aid conservation efforts for the endangered plant. For this, they analysed the germination rate of seeds collected from Andalusia, Spain, in response to different external factors such as cold, heat or smoke. “If you just leave them, very few of these seeds will germinate. What triggers the seeds to grow is the passage of fire. The heat acts as a signal for seeds to germinate, and the removal of large, dense shrubs creates an open space free from competition.

“Although this relationship with fire might seem strange as many sundews in the northern hemisphere grow in wet areas like bogs, the Portuguese sundew only looks like a sundew. In fact it’s the only species in an entirely different genus, and it grows in Mediterranean heathland rather than bogs. These habitats are coming under increasing pressure from land use change and fragmentation, and the species is becoming increasingly rare.”

Fieldwork in progress.
Fieldwork in progress. Photo: Fernando Ojeda

This habitat makes Drosophyllum lusitanicum unusual, even by the standards of carnivorous plants. “It’s the only carnivorous plant that thrives in the hot Mediterranean climate of the heathlands of southwestern Europe”, Maria Paniw, of the University of Zurich, said. “These heathlands stand out from other habitats in Europe because of their high levels of biodiversity. Seeing the sticky leaves of hundreds of Portuguese sundews reflecting the sun against the colourful background of shrubs and flowers is quite a spectacle.”

The Portuguese Sundew and Prey.
The Portuguese Sundew and Prey. Photo: Fernando Ojeda.

Adam Cross added “However, there is much more to this landscape than the plants and animals you see. There’s also a seed bank hidden in the soil, and it is proper conservation and maintenance of this ‘reserve’ of future biodiversity that is essential to the a long-term future of the Mediterranean heathlands.” However, while the Portuguese sundew is limited to just a small corner of Europe, the importance of the research won’t be. “The lessons we’re learning from this distinctive plant in heathlands have implications for conservation management anywhere where natural fires are a regular occurrence, including other biodiversity hotspots around the world. If we want harmony between development and biodiversity then we’ll need to work out a way to better manage fires.”

Reference List

Cross, A. T., Paniw, M., Ojeda, F., Turner, S. R., Dixon, K. W., & Merritt, D. J. (2017). Defining the role of fire in alleviating seed dormancy in a rare Mediterranean endemic subshrub. AoB PLANTS. https://doi.org/10.1093/aobpla/plx036