Ever since Darwin introduced his groundbreaking theory of evolution, biologists have been captivated by the complex processes that enable
What they saw was that traits with higher evolvability were more divergent among existing populations and species, and that traits with higher evolvability were more likely to be different from each other between two consecutive fossil samples.
Conversely, traits with little evolvability or little variability didn’t change very much between populations or between successive fossil samples
Environmental fluctuation is the key
Traits with higher evolvability change rapidly because they are able to respond to environmental changes more quickly, Pélabon said.
The environment – things such as temperature, the type of food available, or any other characteristic important for the survival and the reproduction of the individual – is the driving force of evolutionary changes because populations try to adapt to their own environment. Typically, environments are changing from year-to-year or decades-to-decades, fluctuating around stable means. This generates fluctuation in the direction of selection.
Highly evolvable traits can rapidly respond to these fluctuations in selection and will fluctuate over time with high amplitude. Traits with little evolvability will also fluctuate but more slowly and thus with lower amplitude.
“Populations, or species, that are geographically distant from each other are exposed to environments whose fluctuations are not synchronized. 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,” Pélabon said.
Consequences for biodiversity
The researchers’ results suggest that selection and therefore the environment has been relatively stable in the past. With climate change, things are rapidly changing, and mostly in one direction. This may strongly affect patterns of selection and how species can adapt to environments that are still fluctuating but around optima that are no longer stable even over periods of time of 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,” he said.
Reference: “Evolvability predicts macroevolution under fluctuating selection” by Agnes Holstad, Kjetil L. Voje, Øystein H. Opedal, Geir H. Bolstad, Salomé Bourg, Thomas F. Hansen and Christophe Pélabon, 9 May 2024, Science.
DOI: 10.1126/science.adi8722