‘I am a chemical ecologist, and I investigate plant communication — how plants respond to chemical signals and what chemicals they release in order to communicate with their environment.’

Currently, Dr Clavijo McCormick is exploring the chemical responses of New Zealand native ferns to insect damage. ‘Investigating ferns can help us understand how millions of years of evolution have shaped the ability of plants to defend themselves, since ferns appeared before seeded plants, are generally well defended, have not been selected by humans, and have a longstanding interaction with insects.’

New Zealand has a high abundance and diversity of ferns, including many endemic species, and a variety of insects feeding on them, making it ideal for this type of research.

In order to learn more about the mechanisms ferns use to defend themselves from being eaten, Dr Clavijo McCormick and her post-graduate student Keylee Soriano are using real herbivores and also applying plant hormones to a variety of different fern species, to trick the plants into thinking they have been eaten. Changes in the plants’ chemistry are then measured, to see how they respond in the face of insect damage. The results so far show a significant variation between fern species.

‘We found that species with different growth habits may respond differently to herbivores,’ Dr Clavijo McCormick says, ‘so a tree fern does not respond in the same way as an epiphyte or a bush fern. Epiphytes, or ferns growing on top of other trees, seem to be very active chemically in defending themselves, whereas tree ferns, which are taller and have other kinds of structural defences, seem to be much more quiet in their chemical responses. What it really shows is that there seems to be a diversity of chemical responses in ferns related to the growth habits of the plant and the presence of other adaptations.’

Next, Dr Clavijo McCormick plans to expand the study to investigate other species, and include more work in the field. As well as what the research tells us about our native species, it could also help in the discovery of natural plant products that may be useful in defending crops against insect damage. It could even lead to selective breeding for crop plants that are naturally better at defending themselves. ‘If we understand more about the plants’ self-defence mechanisms, this could help us to be smarter around selecting and breeding plants,’ she explains.

Dr Clavijo McCormick and her team are also investigating the role of plant communication in competition between native and invasive plants. ‘PhD student Evans Effah is exploring the airborne chemical responses of two native species, mānuka and monoao, to invasive weeds in the Central Plateau.’ This is a really wonderful environment that is quite simple in terms of the plants that compose it. But it is at risk because of the rapid spread of invasive species.’

Within the Central Plateau there are different levels of invasion: some areas have high densities of introduced heather and broom, while others remain more or less under natural conditions. Previous studies have shown that plants not only produce chemical responses to being eaten but also when they are facing competition, releasing different chemicals when they are surrounded by others of the same species compared to when they are in the presence of another species. This allows the plants to react in different ways (both morphologically and chemically) depending on whether or not they are under threat of competition.

‘We are exploring how plant communication changes along a gradient of invasion, including how native plants change their chemical profiles in response to invasive species, and vice versa,’ says Dr Clavijo McCormick.

So far, her team, in collaboration with Paul Peterson from Manaaki Whenua — Landcare Research, has characterised the chemical profiles of the species in the study for the first time. She has also gathered preliminary results showing that there is indeed a difference in the chemical profiles of mānuka and monoao when they are in sites where they are competing against invasive species. Next, the team will perform further field and greenhouse experiments to investigate how airborne chemical signals affect plant growth and behaviour both above and below ground.

‘Neighbours matter for a plant — they make a huge difference,’ Dr Clavijo McCormick says. ‘It’s fascinating, and we need to understand what is going on for the plants that are part of our native ecosystems in order to be more effective at preserving these unique environments. When you understand an ecological phenomenon deeply, you have the power to make informed management and conservation decisions.’