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Quick species adaptability shapes long-term evolution

Evolution, the cornerstone of biological diversity, has captivated scientists since Charles Darwin’s remarkable theory. The intricate mechanisms behind how species change over generations remain a source of intrigue.

For years, a pressing question has lingered: can the processes driving short-term evolution within a species, known as microevolution, shed light on the grander scale of macroevolution, which unfolds over thousands or even millions of generations?

A recent study has provided a resounding answer: yes. The research reveals that a population’s ability to adapt rapidly over short periods, termed “evolvability,” holds the key to understanding the long-term evolutionary trajectories of species.

Species evolution across time scales

By meticulously compiling and analyzing vast datasets encompassing both living species and fossils, the researchers have made a remarkable discovery.

The evolvability responsible for microevolutionary changes in various traits, such as beak size, number of offspring, and flower size, can actually predict the degree of divergence observed between populations and species separated by a staggering one million years.

“Darwin suggested that species gradually evolve, but what we found is that even though populations rapidly evolve over the short term, this (short-term) evolution doesn’t accumulate over time,” explained Christophe Pélabon, a professor at NTNU’s Department of Biology and the senior author of the paper.

“However, how divergent populations and species are, on average, over long periods of time still depends on their ability to evolve on the short term.”

Evolvability and species adaptation

The researchers’ approach involved constructing an extensive database containing evolvability measures for living populations and species, gleaned from publicly available sources. They then plotted evolvability against population and species divergence for a multitude of traits.

Additionally, the experts delved into fossil records from 150 distinct lineages, where previous researchers had documented changes in morphological traits over periods ranging from a mere 10 years to an impressive 7.6 million years.

The findings were striking: traits exhibiting higher evolvability displayed greater divergence among existing populations and species. Moreover, these highly evolvable traits were more prone to differentiation between successive fossil samples. Conversely, traits with limited evolvability or variability remained relatively unchanged between populations and fossil samples.

Environmental fluctuations

But what fuels this rapid change in traits with high species evolution? Pélabon attributes it to their enhanced responsiveness to environmental shifts.

The environment, encompassing factors like temperature, food availability, and other elements vital for survival and reproduction, serves as the driving force behind evolutionary change. Populations strive to adapt to their surroundings, which typically fluctuate from year to year or decade to decade while maintaining stable averages.

Highly evolvable traits react swiftly to these fluctuating selection pressures, resulting in significant variations over time. In contrast, traits with low evolvability also fluctuate, but at a slower pace and with less pronounced changes.

“Populations, or species, that are geographically distant from each other are exposed to environments whose fluctuations are not synchronized,” explained Pélabon. “Consequently, these populations will have different trait values, and the size of this difference will depend on the amplitude of the trait’s fluctuation, and therefore on the evolvability of the trait.”

Implications for biodiversity in a changing world

The findings have profound implications, suggesting that environmental conditions have remained relatively stable in the past. However, with the emergence of climate change, our world is rapidly transforming, predominantly in a single direction.

This dramatic shift could significantly impact patterns of selection and species’ ability to adapt to fluctuating environments where the optimal conditions are no longer stable, even over a few decades.

“How much species will be able to track these optima and adapt is uncertain, but most likely this will have consequences for biodiversity, even on a short timescale,” noted Pélabon.

New species and evolution perspective

This study has illuminated a crucial connection between short-term adaptability and long-term species evolution. By unraveling the secrets of evolvability, scientists have gained invaluable insights into the intricate dance between organisms and their ever-changing environments.

As our planet undergoes unprecedented transformations, understanding the dynamics of evolution becomes increasingly vital for preserving biodiversity and ensuring the survival of countless species.

The study is published in the journal Science.


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