What makes plants rare?

Mention the concept of a ‘rare’ plant, and it conjures up images of a brightly coloured flower, deep within the jungle - unseen by human eyes for decades except for an old, dusty picture from an expedition when photography itself was a novelty.

But does actually that make it rare? Simply being hard to find, or even endangered? It was this question that Fenner PhD student Meena Sritharan is searching for an answer to.

“Originally I asked that question and thought it would be certain traits that makes plants rare,” Meena said.

“My honours research was looking if alpine plants were changing through time by looking at plant traits. This led me to think that certain traits may influence the abundance, distribution and or the threatened status of a species – I wanted to question whether it was trait driven, so let’s test this out.”

Meena began by conducting a systematic review of the literature, which looked at certain traits that researchers thought would make plants rare. But when she looked at all the data, Meena found there’s many ways for a plant to be rare, and a list of categorizing traits isn’t actually a definite guide to classifying a rare plant as such.

“In terms of rarity, different researches are interested in different issues in relation to rarity. They might place different emphases on what aspects of rarity concern them, such as if a rare plant is threatened,” she said.

“This may be a problem, if we are looking for ways to fund conservation management, especially regarding threatened species. If we think something is rare, when it might not be – just in that moment in time – we may declare it threatened, and this consequently could affect how we fund conservation strategies.

Meena was discussing this with one of her lecturers, and said that for humans ‘rare’ is something that is one-of-a-kind, like a collector’s item, with only one or two in existence. But in plants it doesn’t quite work that way. 

“Ecosystems change across time, and in one year there might only be a few examples of a species, but in other years there might be more. Then a fire comes through and then there’s hundreds…its abundance may oscillate.”


Researching rarity

To undertake the practical component of her research, Meena spent the last few months down at Booderee National Park, Jervis Bay on the South Coast of NSW. Typically, her day would start early to escape the summer heat, with rulers, measuring tapes and plant identification books in hand.

Surveying specific 10m x 10m plots set up by Fenner School academic Professor David Lindenmayer and Chris MacGregorin the bush, Meena would merticulously collect data, documenting the number of plants bit by bit.

“Currently where I’m coming from - to see if plants are rare - I think it depends on the environment in which a plant grew up in that controls its abundance and distribution - not the traits of the plant itself.”
Human perception can play a part as well. Meena described how sometimes you think you’re seeing a pattern, but it might be localized to the small sample size of the space that you are working in.

An ironic twist demonstrated exactly that, as Meena came across a single dandelion flower on one of her last days.

“It was frustrating, I had done the entire site and had got to the last box. I remember thinking to myself – ‘what are you doing here, you look like a rare plant but you’re not!’”

Working alone outdoors for such a long period of time had its own benefits and drawbacks for Meena. She said it was fantastic to be outside all the time, and was a chance to learn completely new skills including operating a four-wheel drive vehicle. But she also learnt the importance of debriefing after the time spent in the field.

“Being alone all the time can also mean that you’re stuck in your own head, and with your own thoughts for a long time. I found it really important to be able to call up a friend at the end of the day to talk about my work, and whether the day was successful or not. Otherwise I’d only have the cat in the house I was staying at to talk to!”


Implications for conservation

Over the next few months Meena will have to analyze the data, and see if there is a management implication from the identification of rarity.

“I think we have to somehow move away from the idea of just looking at traits to identify rare plants. In some of the research I’ve looked at people assume that if we know the traits of rare species, we probably know the traits of threatened species, so we find plants with these traits then ‘deduce’ that they are more likely to be threatened.

“This doesn’t take into account the complexities of much wider systems – we need to look at the ecosystem as a whole – was it affected by a fire or invasive species or whatever, and then use this contextual data to see if it may influence a plant in being rare, common or threatened.”