Zoe Xirocostas (she/her), UNSW Sydney

Plant introductions are undesired in most parts of the world, Australia especially, as they are the precursor to the thousands of invasions that threaten biodiversity. These pesky introduced species can have devastating impacts on the native ecosystems they inhabit by altering food webs, increasing resource competition, and can even lead to extinctions in extreme cases. On an economic scale, introduced plants can really pack a punch, costing a globally estimated $120 billion per year in lost crop yields and management efforts. Therefore, it is not surprising that there is great interest in the field of invasion biology that focuses on how and why introduced plants can succeed in their novel ranges. In particular, the enemy release hypothesis, an idea which states that species may do better in new habitats because they’ve escaped their co-evolved predators, herbivores, and pathogens, is one of the highest explored concepts in the field.

But what seems to fly under the radar, is that if introduced plant species are leaving their enemies behind, then surely they are missing their friends as well?

Specifically, I wanted to know whether plants were losing their pollinators when they moved to a new range. To find out, I went on an incredible whirlwind experience that can only be described as a scientist’s version of the Amazing Race. I spent over 8 months in the field staring at flowers in Spain, England, and Estonia (native range) and NSW, ACT, VIC and TAS (introduced range) and recording the animals that interacted with them. In the end, I clocked up over 120 hours of observation time and recorded 2652 floral visitors.

Unsurprisingly I found that plants in their introduced range were in fact receiving far fewer visitors in terms of abundance and richness than plants in their native range. On top of that, the community composition of these visitors varied considerably in 7 of our 10 target plants. I also compared these data to the magnitude of enemy release these plants received (quantified in another study from my PhD) and found that plants are more likely lose and then regain fewer enemies than they do pollinators, in their novel habitats.

This is huge, because it means these introduced plants are still finding a way to persevere despite having fewer pollinators around. It also allows us to ask questions like: are these plants self-fertilising and rapidly evolving to no longer need pollinators? Or are these fewer pollinators fulfilling plants’ reproductive needs to the same level as the native range?

My research helps to shine light on, and supports, an often underappreciated mechanism in invasion biology, missing mutualisms, which suggests that invasions may fail because key mutualists are left behind. Moving forward, I would love to see researchers explore other positive interactions that could be lost in the introduced range, like seed dispersers, mycorrhizal fungi on roots, or predatory mites housed in domatia, to understand how they may hinder the invasion process. If we want to further our understanding of how species become invasive, which can help us to predict and prevent future invasion, then we must consider both the positive and negative interactions that are likely to play a role.

I would like to acknowledge the Dharug, Eora, muwinina, Ngarigo, Ngunnawal, Nuenonne, Paredarerme and Woiworung people who are the Traditional Owners of the lands where this research was undertaken. I would also like to sincerely thank all the research assistants that helped me collect data in the field and the ESA for granting me a Student Award to support my work.

If this blog post has intrigued you and you’d like to hear more, contact Zoe via email () or Twitter (@zoexiro), or join her speed talk and poster presentation at ESA-SCBO 2022 in Wollongong this year!