From Cytogenetics to Ecosystem Ecology: A Journey of Discovery with Valeria Souza

The Source
By: Guest contributor, Mon Mar 6 2023

Author: Guest contributor

Valeria Souza started her scientific career studying biology and cytogenetics but found out that only through ecosystem ecology could she find the answers to her questions ever since a young age. She was later invited by NASA to conduct a seminal work on astrobiology at the Cuatro Cienegas Basin, a small oasis in northern Mexico. The author's pursuit of knowledge led her to study eco-evolutionary feedback, human impact in ecosystems conservation and support local children in learning more about their territory ancestry and importance for the history of life. She believes that the field of ecosystem ecology can benefit from greater gender diversity, as seen in her lab and at UNAM, where women are equally represented and encouraged to pursue their scientific interests.

What inspired you to pursue a career in the ecosystem ecology, and what do you find most rewarding about your work?

I started with biology as an undergrad in order to understand diversity and its relationship with DNA. However, even after I did my undergrad and master dissertation on cytogenetics, I realized that DNA in chromosomes had not the answer to my basic question since I was a girl: how a simple molecule could hold the key to the natural world we know? It was, Luis Eguiarte, my husband that convinced me to turn my eyes toward ecology and more specifically to population genetics of microbes. I did my PhD dissertation in the diversity of Rhizobia along a domestication gradient and realized that the domestication level as well as the environment had a bigger role than I expected on genetic diversity. Somehow, ancient Mesoamericans domesticated beans along with their symbionts and with the rest of the milpa (corn, squash, chile and many under described herbs). Later, in my posdoc, I really learned evolution with Richard Lenski long term experiment. Returning home to Universidad Nacional Autónoma de México (UNAM) in 1993, we started the lab with a series of basic questions: Why and how E. coli becomes a pathogen, while Rhizobia is a nitrogen fixer that help legumes to grow in poor soils? What is the role of genetic diversity and microbial sex in these contrasting strategies? 

Then, everything changed, in 1999, NASA came knocking the door and ask us (Luis and I) to participate in an astrobiology project in Cuatro Cienegas Basin, an oasis in Northern Mexico that is particularly rich in stromatolites and microbial mats, suggesting that it could be a model of early Earth, since it was extremely poor in nutrients. Our task was to describe the basic microbial diversity in the ponds and microbial communities. However, as always, I wanted much more. I realized that the extraordinary microbial diversity of this oasis could only be understood as a whole, by looking at all scales, from particular genes, to genomes, to population genetics, to community assembly, to nutrient cycling, to geologic scenarios, to the story of life on Earth. 

These apparent “jumps” in my scientific career are only the reflection of looking for answers and the joy of discovery that there are always more questions that challenge your frame of mind. Each new pursue follows an “eureka” moments that make you feel “Enlighted”. 

My child question took me into a knowledge adventure and the answer is, till now: DNA can hold nature by always changing in response to hunger. In order to eat, and therefore grow and reproduce, the most basic of need in natural selection. Organisms are exposed to a moving challenge that is the interactions between members of their community. This tension between who eats or get eaten (mostly by viruses) leads to a constantly changing environment and hence a change in their evolutionary response. This is called eco-evolutionary feedback and DNA is just the “data logger” of the long pursue of food along the long long history of life on Earth.

How do changes in land use, such as converting natural habitats to agricultural fields, affect the diversity and abundance of species within an ecosystem?

At the same time that we started to discover the geological reasons for the water in this extraordinary oasis of the Cuatro Ciénegas Basin (CCB), a butterfly shaped valley in the middle of the Chihuahuan dessert. We started to wonder the role of tectonics in it (why the butterfly shape with a central “body” la Sierra de San Marcos). As I followed geological maps of the area learning that a very large system of faults feed the system by connecting CCB deep aquifer to the Northern valley of Ocampo and the Southern valley of Hundido. At the same time, a large operation was starting in Hundido to increase the area of alfalfa fields, all of them watered by the same deep aquifer. Therefore, if water extraction occurred in any of the connecting points, extinction of the wetland would follow. This was 2002 and the battle for the water started in earnest, we could stop it by demonstrating to the federal government our hypothesis. 

We did it with DNA fingerprints of the water communities of the 3 valleys that they were connected, using for the first time in Mexico environmental DNA. To make a long story short, they closed the key fields in Hundido for a while, and then reopened then as the government was not watching. We found out that, through the identity of the bacterial communities, that the deep aquifer was ancient and was part of the Sierra de San Marcos, and that such Sierra still had magma in its depths and that heat feed the wetland, while the wetland feed the deep aquifer. Such connection was broken in 1970´s by a series of channels whose sole purpose was to dry the wetland and they still do it, despite ferocious battles. Meanwhile we described that the enormous diversity of this site was due to time, a very long time of isolation by the mountain deep sediments that contained ancestral lineages that evolved isolated from everything else. CCB was an endangered time machine, the first wetland to be doomed toward extinction was the Churince (see the Book Series Cuatro Ciénegas Basin: An Endangered Hyperdiverse Oasis) since its gypsum base was a little higher than the rest of the valley. We started to work in a large group with a grant from Fundacion Slim in 2010. The aim was to describe as much as possible as fast as possible before the system collapsed. It did in 2016, as we wrapped up the project. Its glorious lagoons lost to the stupidity and shortsighted politicians. Mexican water law is designed for corruption. That is why, after 23 years of work this March, 2023 is our last trip. My hearth cannot bear more dead turtles and dead fishes. 

The good news is that, during those years, we have been empowering the kids at CCB since 2004, and in 2010 we put a molecular ecology lab in their school. As a results of the kids understanding their site, society has also changed. These kids take awareness through art classes since preschool and harness science in high school. Now they can hold the reins of their wetland and defend what is left. Is their land and they know the value of their genetic recourses, they are the owners and the bio prospectors.

How can the field of ecosystem ecology benefit from greater gender diversity?

In our lab girls are always welcome, as well as boys, and they are not shy, since the boss is a ferocious woman. Many of my alumni are microbial ecologist with their own labs now and trail blazers’. I am very proud of them. Also at the rural school of CCB, more girls than boys enter the molecular lab and they get then empowered and supported to go to college, something unhear off some years ago. I think that at UNAM women representation in our institute is pretty balanced. A woman is now our director, she was my first PhD student in the CCB project, and she learned that nothing is impossible, you just need to persist.

What strategies can be implemented to ensure the participation and leadership of women in ecosystems ecology?

I believe in teaching through example and to be a strong woman in science is a start. Then, you have to explain girls at any age: elementary school middle school, high school, college that they also can. The message is that they rock, they just need the will and the purpose to not be defeated and yes, you can have it all, a loving family and a career, it just takes discipline and choosing their battles. You can also be a patient mentor and translate science at all levels. But, most of all, show passion for your work (that is the easy part).

How can conservation organizations work with local communities to empower women and increase their participation in conservation efforts?

NGOs as well as universities have to teach to be bold and give kids the needed opportunities. In our case we have partnered with Fundación LALA (our previous enemies, now converted allies), Fundación Slim, Pronatura, and Alianza Cuatro Cienega’s 2040 to support education at all levels. Scientist from our group, mostly strong women, always make a point in teaching to the high school at CCB what have we done in the last year, what have we found and where are we going. They know we put ourselves in the line to save their paradise, that is why it is now the time to surrender the conservation effort to them, handle the torch to the next generation of protectors.

Can you tell us about your current research and how it relates to Sustainable Development Goals?

I just moved from the desert oasis that holds the story of ancient oceans, to the actual, endangered sea. We have two new projects, one in Chilean Southen fiords in the Magallanes region, where, supporting precisely an ex student and friend, Paola Acuña, by empowering the CEQUA (Centro de Estudios del Quaternario y la Antartica). Together with her team we are looking to understand the effect of the Anthropocene in this, otherwise, pristine nature. In order to do so, we are studying the microbiome of the skin, plumage and surface of 2 species of pinguins, 2 marine mammals, 2 fishes and 2 crustacean species as well as kelp and its response to the holobiont (the animal and its microbes) to changes of temperature, salinity and UV a and UV b. To do so we are using genetic markers to describe microbial diversity, transcriptomics to “listen” to their most expressed genes of the holobiont, metagenomics in order to understand the context of those messages, and population genomics of the 9 keystone species. This project also involves oceanographic, environmental, climatic and UV light sensors in order to understand “the ecosystem” in a holistic way. Microbes as biosignals of danger in the most sensible part of the world, a geography that in influenced by 3 oceans. We just render our 2nd year report out of 5.

The 2nd project will start this year and is to partner with German fertilizer producer Proman and their Mexican representation (GPO) that will build a plant in the coast of Sinaloa in the sea of Cortez. The caveat is that the bay where the plant will be build is extremely polluted and they promise to clean it and kept it clean. That is why they looked for me as microbe whisperer to design a strategy along QB4 a newly made environmental compagnie that is also lead by a woman and together we will clean the ocean using wetlands along with microbial consortia that supply “the broken parts of the clock of life” meaning the missing parts to close the Nitrogen and Carbon cycle. We will do first a base line description of the diversity of the bay using metagenomics-transcriptomics in order to confirm our hypothesis, that the biogeochemical cycles are broken by our intrusion into fossil carbon and the production of agrochemicals, including ammonia that is present in excess in the oxygen depleted bay. The second phase is to work along the fertilizer company in order to explain sustainable agriculture to the ranchers of the area, to produce more, they need micro doses of agrochemicals, not tons. The compromise with Proman is that if we achieve the restoration of Ohuira, the world is next, they have the capacities to really change the world.

The common theme in both pursues of sustainability is to teach capabilities to the local people and mostly, to inspire young girls to take the lead and, just like in CCB, handle to them the torch of the planet future.

What advice would you give to young women interested in pursuing a career in your field of work?

Do not be afraid, be bold, follow your instinct and mostly enjoy the ride.

Learn more about Cuatro Ciénegas and Valeria’s work by accessing the Cuatro Cienegas book series and visit our SDG 15 hub for selected research about Life on Land

About the author

Valeria Souza © Springernature 2023

Valeria Souza has a bachelor’s degree in Biology, master’s degree in Genetics and PhD in Ecology from the National Autonomous University of Mexico (UNAM). In 1990 Valeria worked with Rich Lenski at Irvine California (UCI), where she gained experience in experimental evolution. In 1993, she took on a research position at UNAM in Mexico, where she still works today. She was one of the first researchers worldwide to study the  evolutionary ecology of microbes. In 1999, Valeria and Dr. Eguiarte were invited by NASA to explore a new world on an expedition that led them to study microbial biodiversity in an unlikely oasis in the Chihuahuan desert. She is an international honorary member of the American Academy of Arts and Sciences.


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