Living world in the light of evolution
Nishide: What made you start studying evolution?
Dr. Pearse: Because evolution links everything together. There’s a frequently quoted saying that “Nothing in biology makes sense except in the light of evolution” (*). Evolution is what caused life, and so if you want to understand life, you must understand evolution.
(*) From the famous 1973 essay “Nothing in Biology Makes Sense Except in the Light of Evolution” by Theodosius Dobzhansky, a Ukrainian-born American geneticist
Nishide: Charles Darwin and Alfred Russel Wallace were famous 19th century British biologists and naturalists, but do they still influence science today?
Dr. Pearse: Yes. Darwin and Wallace developed the fundamental theories of biology. Before they proposed the concept of evolution, there were no biologists in the real sense of the term. People were just observing things and writing down what they saw. Evolution is to biology what mathematics is to physics. Without math, physics would be just people dropping things and saying, “Oh, wow. It goes down.”
Evolution theory lets us understand how things in biology are linked. It allows us to understand how one species enters a new environment, differentiates and forms an ecosystem.
Morimoto: Could you explain Darwin and Wallace’s hypothesis in more detail?
Dr. Pearse: Sure. Darwin and Wallace came up with the remarkable idea of “natural selection,” which drives evolution. Animals and plants show various individual differences, and those that are well-adapted to their environment leave many offspring, who are also well-adapted. Meanwhile, individuals that are not as well-adapted don’t leave as many offspring, and in some cases, they die. In other words, natural selection occurs when there are differences in fitness between individuals.
Taylor: Is natural selection driven by physical characteristics that interact with the environment? For example, longer beaks or longer legs?
Dr. Pearse: That’s a good question. Natural selection involves all kinds of characteristics, including physiological features and behaviors, but physical characteristics are most commonly discussed. Darwin’s finches in the Galapagos Islands are a good example. After Darwin’s death, during droughts in the 1970s and 1990s, researchers observed real-time changes in the finches’ beak sizes through natural selection. The drought changed the types of seeds available for the finches to eat. As a result, their beak sizes changed to better handle the surviving seeds.
Dr. Will Pearse studies evolutionary ecology at Imperial College London.
Correlation between cherry blossom flowering and temperature
Nishide: In your research, you’ve analyzed the relationship between cherry blossom flowering times and average temperatures across East Asia.
Dr. Pearse: Yes. I was fortunate to work with data that had been continuously recorded for over 100 years. This data includes not just cherry blossoms but other plants and animals as well. It’s truly remarkable. While ecology as a discipline is only about 100 years old, I’m deeply impressed by the foresight and effort that went into maintaining standardized measurements across Japan for over a century.
What really surprised us was the correlation between that temperature and cherry blossom flowering dates of the year. The relationship was so strong that we spent extra time before submitting our research paper because we thought there must be some mistake. We had never seen such a close correlation before.
Morimoto: Indeed, I can feel that cherry blossoms are blooming earlier than before. When we were children, cherry blossoms were the flowers that celebrated school entrance ceremonies in April. Japanese schools start in April and end in March, so cherry blossoms used to mark the beginning of school life. Now they bloom in March and have become the flowers for graduation ceremonies that mark the end of the school year.
Dr. Pearse: The problem is that all the plants we analyzed in the dataset are responding to temperature changes at slightly different rates. This means that the sequence of plant flowering times is changing within the ecosystem.
While humans can adapt even though cherry blossoms bloom at different times—it just means we can’t use them as reliably for timing school events anymore. However, this could have devastating effects on insects and birds that directly or indirectly depend on cherry blossoms. We need to pay attention to how species’ communities are being reorganized and how these creatures work together. This is crucial because ecosystem services like carbon sequestration and crop pollination are vital to us.
Seeing such close correlations progressing at different rates for different plant species is somewhat concerning. It’s like everyone on a highway deciding to drive at different speeds, which could lead to many problems.
Yoshitaka Morimoto works on decarbonization research at Hitachi Europe.
Meaning behind the earlier cherry blossom front
Nishide: From an evolutionary perspective, how would you explain the reason why cherry blossoms are blooming earlier?
Dr. Pearse: Cherry blossoms are blooming earlier because they’ve evolved to flower when they can access resources suitable for growth. Cherry trees want to bloom when it’s warm enough and grow as much as possible. The more they grow, the more offspring they can produce.
As a result, cherry trees have evolved to respond to specific climate and weather conditions as triggers for flowering. This is how they survive and thrive. The problem is that other creatures, including humans, that have come to depend on cherry trees have evolved to respond to different triggers.
Taylor: Can cherry trees sense light and temperature?
Dr. Pearse: There’s extensive previous research in this field, so I should be careful in my response, but it’s likely a combination of multiple factors. One is “photoperiod,” the length of daylight. Temperature acts as a kind of trigger, but it’s not just temperature alone; it’s also about the accumulation of days with specific temperatures. In other words, it’s not just about the temperature on a particular day, but potentially about how many days of temperatures above, say, 10 degrees (I presume everyone will know this is Celsius?) have accumulated.
Nishide: These responses come from adaptation to changing environments, but if we consider a tree’s lifespan — say, 100 years — the changes we’ve seen in the last 30 years represent a relatively short period. Can evolutionary theory explain changes over such a short timeframe?
Dr. Pearse: That’s a good observation. Evolution is all about the next generation. Evolution has shaped how plants respond to their environment. Natural selection, which Darwin discovered, is a process that removes individuals that aren’t well-adapted. Those that aren’t sensitive to appropriate climate conditions die out and can’t leave offspring.
Cherry trees are finely tuned to respond appropriately to their environment. Evolution didn’t instruct cherry trees to bloom on March 1 every year; instead, it produced cherry trees that are calibrated to respond to day length and temperature. It gave them flexibility.
Therefore, it’s natural for cherry trees to bloom at different times each year as climate change alters conditions. This is adaptive and beneficial for their survival and prosperity. In other words, cherry trees’ sensitive response to temperature changes is due to past evolution giving them this adaptive capacity.
Imperial College London (Silwood park), where the roundtable was held, is blessed with a lush green natural environment.
The theme of Vol. 3 will be “Restoration of Diverse Ecosystems.” Why is it essential to maintain and restore biodiversity? We will explore what we can do to address the biodiversity crisis while learning from the culture of our ancestors, who maintained diverse ecosystems by living in harmony with nature and caring for their surrounding environment.
(In collaboration with Imperial College London)
Related Link
Profile
Will Pearse, PhD
Reader in Evolutionary Ecology,
Imperial College London
Dr. Pearse is a Reader in Evolutionary Ecology at Imperial College London, where his lab develops new tools to better measure and forecast biodiversity and human health to help drive societal change. His research focuses on developing new computational methods to understand how species' evolutionary history drives their present-day interactions. He enjoys working with companies (such as Hitachi) and charities (such as the EDGE of Extinction program) to apply insights from his lab's research and so support nature and human-wellbeing.
Paul Taylor, PhD
Laboratory Manager,
Sustainability,
European Research and Development, Hitachi
Dr. Taylor studied environmental science and received his PhD for developing statistical models to assess the quality of measurement in environmental surveys and associated risks from misclassification error. His subsequent career as a sustainability specialist for corporates has spanned various industry sectors and sustainability topics, including carbon accounting for products and supply chains, responsible sourcing for metals used in electric vehicles and innovation in the mining sector. His role for Hitachi research and development focuses on innovating future technologies in sustainability, such as reducing CO2 emissions, improving the lifecycle impacts of batteries or protecting and utilizing nature for climate adaptation.
Akinori Nishide, PhD
Chief Researcher,
European Research & Development Centre,
Hitachi Europe, Ltd.
Dr. Nishide is a chief researcher at Hitachi Europe, Ltd., focusing on developing monitoring, reporting, verifying metrics on biodiversity and models to evaluate an economic value of biological ecosystem as a complex system. He has studied condensed matter physics and has joined the R&D of Hitachi, Ltd. in 2010, then, received his PhD for studying the effect of the quasiparticle on the electric state in the thermoelectric material. On the occasion of studying at the Max Planck institute in 2019, he has started the study on the complex system.
Yoshitaka Morimoto, Ph.D.
Deputy Lab Manager of Sustainability Laboratory,
European Research & Development Centre,
Hitachi Europe, Ltd.
Dr. Morimoto joined the Central Research Laboratory of Hitachi, Ltd. in 2011 after completing his PhD in Electrical and Electronic Engineering. Since then, he has been involved in the R&D of optical measurement techniques, such as defect detection for 2.5-D semiconductor stacking. After completing his MBA, he joined ERD as an expatriate. His current role focuses on customer co-creation for hydrogen technology to decarbonize the gas transmission and distribution sectors.
