In Insights we discover the story behind a recent publication in Functional Ecology. What inspired the authors to do the research and how did the project develop before the publication? and what wider impact might their work have?
This week, Anamarija Žagar talks to Bjorn about her paper on the performance of two co-existing lizards in Slovenia and the role of functional and morphological traits. Anamarija currently works at the National institute of Biology in Slovenia, and is also affiliated as a research associate to the CIBIO Research Centre in Biodiversity and Genetic Resources at the University of Porto in Portugal.
What is your paper about and how does it links with other work from your lab?
This work found its origin in the broader research on lizard ecology at CIBIO. We studied two small lizard species that – at first sight – are remarkably similar in appearance, and lack obvious spatial, temporal or other segregation. Such ecologically similar species have a high potential for interspecific competition. To gain insights into how such species can co-exist, we decided to investigate their functional morphology and whole-organism performance traits. Our results show that the species differ in two important functional traits: bite force and climbing speed. Both traits are linked to corresponding morphological traits. This was a very insightful contribution to the existing knowledge on the studied pair of species and exemplified the role of functional traits in the mechanisms driving lizard co-existence, which is common in natural communities. Moreover, our results could be interpreted in great depth due to extensive background knowledge on the functional morphology in lizards, which have been studied for over a decade by co-author Antigoni Kaliontzopoulou and other research teams in this field.
From the introduction, it seemed to me that there was a difference between the two lizards in the trade-offs between the benefits and costs of thermoregulation (i.e. being able to live at higher altitudes versus high energetic costs), and that co-existence patterns were driven by how these trade-offs play out on aggressive behaviour. Is that right?
Yes, our previous research revealed that the studied species differ in the precision of thermoregulation. Species more abundant at higher elevations are more precise thermoregulators and invest more energy in behavioural thermoregulation. In earlier staged behavioural experiments, we observed that aggressive antagonistic interactions negatively influence the thermoregulatory ability of the high-altitude species. As a corollary, it was more often chased away by the more aggressive low-land species. This provided us with part of the answer in understanding the mechanism of the species co-existence/segregation pattern observed in natural populations. But we did not yet understand if the dominant role in aggressive behaviour was underpinned by functional morphological and performance traits (for example, stronger bite force, which would give them advantage in direct fights where males often bite each other in the head). We also did not know anything about their comparative locomotor performances that are crucial for several ecologically important aspects, such as escaping predators, catching food, etc.
Many of us have a very limited idea on how you capture enough lizards for a study like yours. How do you go about catching a good quantity of lizards?
Lizard field-work is limited to sunny warm days, when these reptiles are active. Catching rock lizards thus involves a lot of time spent outside in nice sunny weather. The species we study in this paper are rock lizards, which mainly live on rocky surfaces. These include vertical rock crevices, which can be difficult to access. In such habitats, they are easiest to catch using a noose that is attached at the end of a long stick (2-3 m). We actually use foldable fishing rods that are easy to carry to the field. Catching involves also a big bag of patience, slow movement and standing motionless for up to half an hour waiting for a lizard to re-appear from their shelter. It can also be quite frustrating when wind is moving your noose. Once the noose is placed around the lizard, you simply lift up the rod and soon the lizard is in safely in your hand.
I was intrigued further by your measurements on sprinting and climbing speed. You mention that you used a cork substrate on a racetrack. These species, however, live on rock. How representative are these measurements?
Cork is a frequently used substrate in lizard running experiments because it provides several advantages. It is easy to obtain and standardize across experiments, as obtaining thin cork leaves at the market is relatively straightforward. For the lizards, it is a good general substrate, as it provides good traction, and it is therefore not stressful for them. Through trials with different substrates, we have found that – although it might not seem intuitive at first – cork is in fact a substrate that imitates natural settings quite well, being compatible with the biomechanical and physical characteristics of our study organisms. For instance, when trying to use sand paper as a substrate to more closely approach the surface of a rock, we found that at high inclinations the lizards would struggle to climb the running corridors, and that sand paper in fact is detrimental to them as it wears their nails. Note that in our study, we are comparing the relative performance output, thus using the same substrate for climbing and running experiments was crucial. On the other hand, using a stone substrate could have been more realistic, but would also be difficult to carry around when we combine experiments with fieldwork in remote locations, and it is also quite difficult to standardize in terms of micro-structure. For these reasons, cork seems like a good option, being both relatively realistic and technically convenient.
The two lizards, despite living together, seem to have undergone different evolutionary pressures. What do you think the effect of climate change will be on co-existence patterns?.
In order to really comprehend the full range of climate-change effects on animal species, we clearly need to think beyond single-species systems. We would, for example, need to integrate our understanding on the effects of abiotic factors on a given species with knowledge how this species interacts with other species in the community. In the case of ecologically similar and co-existing species with opposite altitudinal pattern, like my lizards, the predicted increase of environmental temperatures may cause the low-land species to spread towards higher-altitudes. Consequently, they will increasingly come into contact with the high-altitude species and so it is crucial to understand what interactions between the species can be expected, especially under what conditions they will co-exists and when one species can displace the other. This will help us to assess the potential threats that climate changes might have on them and which species are more vulnerable.
And one last question: when you are not chasing lizards, what do you do?
I only sleep, eat and chase lizards! No, there are also several other important and interesting things that keep my days busy. I’m a very sociable and outdoor person. Because I spend most of the time in Slovenia, this gives me a great opportunity to be outside in nature. I am trying to spend my free time surrounded with family and friends. I enjoy going for hiking trips, camping, mountaineering. In Slovenia, we also have a strong NGO community in nature conservation and I participate in different activities of the herpetological society that mostly focus on education and conservation activities, which I think are very important. I also sing in a singing choir Kombinat, where with my friends we share the view that it is important to be informed on current situation in society and be aware of any injustices or discriminations and react by pointing them out, using songs and music.
Further information about Anamarija’s research can be found on: https://cibio.up.pt/people/details/anamarija and https://www.researchgate.net/profile/Anamarija_Zagar