Ana Salgado: Butterfly oviposition preference affects offspring survival

Dr. Ana Salgado shares with us the background behind and synopsis of her paper “Narrow oviposition preference of an insect herbivore risks survival under conditions of severe drought”, as well as her experience in becoming an ecologist, her hobbies, and why this project has been her favorite so far during her academic career.

About the paper

What’s your paper about?

We assessed the microhabitat conditions that are related to female oviposition preference of the Glanville fritillary butterfly (Melitaea cinxia) and linked these conditions to the survival of the offspring. To do so, we measured in detail the habitat conditions of 12 populations where the butterfly is present in the Åland Islands (Finland). We divided each of these habitats into cells of 400 m2 to collect detailed information about the microhabitat conditions and their variation over time (2015-2018). We combined the detailed microhabitat information with 10 years of georeferenced larval nest and precipitation data to determine habitat selection. We found that females preferred microhabitats with high host plant abundance and sites where host plants often show signs of drought stress. Furthermore, we found that in most years the larval nests located in these drought-stressed microhabitats have a higher over-winter survival, but in an extremely dry year (2018) most of the larval nests found were dead by the end of the summer. Our results thus suggest that females continued choosing drought-stressed microhabitats for laying eggs even in the dry year, but with a drastic consequence: the decline of the butterfly population by the end of the summer.

Typical landscape where the Glanville fritillary butterfly can be found in the Åland islands (Finland). Photo credit: Ana Salgado
Typical landscape where the Glanville fritillary butterfly can be found in the Åland islands (Finland). Photo credit: Ana Salgado

What is the background behind your paper?

Environments have been exposed more frequently to more severe climatic conditions in the most recently past decades, and understanding how organisms are coping with such unusual variation is of importance for the longterm survival of natural populations. Furthermore, the direct effects of climatic conditions have been studied a lot over the past years from different taxa, whereas much less is known of the indirect effects of climatic conditions. For example, those indirect effects imposed via drought on host plants and how they are then translated over the life-history traits and behaviour of the organisms feeding on the plants. The Glanville fritillary butterfly in the Åland islands is a great model system to study responses to climatic conditions in their natural habitat, and there is great variation in the climatic conditions occurring within the islands, with an increasing frequency of drought during summer, which push the species to respond in order to survive.

What are the key messages of your article?

The key message of the article is that adjustable behavioural preference is important when experiencing variable climatic conditions. In our case, female oviposition preference for drier microhabitats give a survival advantage in regular years when the climatic conditions are favourable for the Glanville fritillary butterfly. However, this narrow habitat preference for drier microhabitats had a drastically negative impact on the population when the climatic conditions got more extreme. As we observed in 2018, the females were not able to fine-tune their habitat preference according to the extremely dry conditions experienced and their offspring had a reduced survival by the end of the summer.

How is your paper new or different from other work in this area?

Our paper presents two key components that are not combined often in other works. The first highlights the use of a long-term demographic dataset even for more behavioural questions, which here has helped us to determine how narrow the female habitat preference is for this butterfly. The second component is that we used this model system to include the indirect effects of drought into the responses of the organisms. So far indirect effects of climatic conditions are little explored.

About the research

What is the broader impact of your paper?

Our paper highlight how species well-adapted to live on the border of their range limit margins maybe become highly vulnerable when the climate changes as the variability required for adjustment may have been lost.

Did you have any problems setting up the experiment/gathering your data?

Ana georeferencing larval nests in a rainy day of summer 2015. Photo credit: Paula Salonen
Ana georeferencing larval nests in a rainy day of summer 2015. Photo credit: Paula Salonen

While choosing the locations to work with, we decided to include meadows, roadsides, pastures and gardens, which represent different types of areas that the Glanville fritillary inhabits in the Åland Islands. During the first field season, we encountered some problems with sites that were a bit too close to residences. For example, one site was a farm where cows could walk freely between the milking parlour and the pasture where they eat. The larval nests were within the cow trail and we were not able to set our tags or our data loggers on the field with the risk of cows eating them. Thus, we decided to stop monitoring this specific location.

Where you surprised by anything when working on it?

I was surprised to experience the driest summer ever recorded within the history of the survey of the butterfly metapopulation. In summer 2018, we were not supposed to conduct any surveys, however the opportunity arose, so we decided to take advantage of it. We went to the field and measured the drought effects on the habitats. Such a decision was crucial for understanding females’ behaviour towards extreme climatic conditions and the consequences for the offspring.

About the Author

How did you get involved in ecology?

Ana Salgado Photo credit: Lucía Maldonado
Ana Salgado Photo credit: Lucía Maldonado

I am from Ecuador, one of the countries with the highest biodiversity in the world, thus it is hard for me not to be mesmerized by plants or animals. I guess that observing such a diverse environment while growing up got me focused on and interested in nature. I remember when I had the opportunity to visit the Galapagos Islands for the first time at the age of 12. I was intrigued by the unique species inhabiting the islands and how they are adapted to their environment. However, it was not until I began studying biology at university when I became involved in ecology. I got immersed in the field of behavioural ecology while studying glass-frogs and their parental care in the cloud forests. Later, I became interested in studying butterfly community composition in dry forests. I continued my master’s studies looking into the gene expression of defence-associated genes in a moth and relating to its host plant defences, and this then led me to do my PhD project on understanding the indirect effects of drought in plant-herbivore interactions. I recently graduated from my PhD and I am happy to be able to call myself an ecologist and share my science.

What project/article are you most proud of?

I would say that this project is the one chapter of my PhD that I am most proud of because I was able to combine my interests about environmental variation and how animals respond to it. While working on this project I discovered my interest in plant-herbivore interactions and how environments are shaping both plants and animals’ way of living. I also appreciate this project because I put a lot of effort into collecting data over many months in the summers. I also learned so much from producing this paper as this was a collaborative work with my co-author Michelle DiLeo and my supervisor Marjo Saastamoinen who supported us in developing this project.

What is the best thing about being an ecologist?

As an ecologist that has spent a lot of time in the field to conduct research, I would say that the opportunity to be close to nature and observe it is the best thing. I have been able to explore pristine places and see magnificent organisms, and having the opportunity to study them and discover how they live and share such findings with others are the best parts about working in this area of science.

What do you do in your spare time?

I like to do handicrafts and I am constantly knitting or crocheting because I find it very relaxing, and I use that time to prepare gifts for my friends and family. Recently, I started to paint with watercolours, and I am happy to bring drawing back in my life. I also like to do some sports; I especially like to ride my bike and do yoga. During the summer I like to play volleyball and swim. Meeting my friends for some fun is also part of my spare time.

Read Ana’s article here.

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