In the world of biology, the concept of fitness is often seen as the ultimate determinant of success. But a recent study published in the Journal of Statistical Mechanics: Theory and Experiment challenges this notion, revealing that the environment and expansion speed play a crucial role in the survival and dominance of species. This research, inspired by the behavior of bacterial colonies, uses mathematical models to demonstrate that fitness alone is not the sole factor in determining the success of a population. Instead, the study highlights the importance of the expansion speed and position along the growth front, as well as the spatial structure of the population.
The study's central model combines the KPZ equation with the Fisher equation, two fundamental models in evolutionary biology and physics. By distinguishing between competitive advantage (fitness) and expansion speed, the model reveals that a population's success is not solely dependent on its fitness. Instead, the balance between these factors determines the shape of the growth front, which can be a rounded bulge, a composite bulge with sloping sides, or a V-shaped dent.
One of the most intriguing findings of the study is that a less fit population can thrive if it occupies a favorable position, such as a peak or protrusion. This means that the ancestors of a population may have been in the right place at the right time, ensuring the success of their descendants. Conversely, a population with a competitive advantage may fall behind if it expands more slowly, highlighting the importance of timing and position in the survival of species.
The study's findings are supported by experiments on microbial colonies, which have shown that the shapes of the expanding front predicted by the model closely resemble those observed in real-world populations. However, the study's authors caution that the underlying mechanisms are not yet fully understood, and further research is needed to test the conditions under which these mechanisms operate in real populations.
In conclusion, this study challenges the traditional view of fitness as the sole determinant of success, revealing the importance of the environment, expansion speed, and spatial structure in the survival and dominance of species. By combining mathematical models with experimental observations, the study provides a deeper understanding of the complex dynamics that shape the natural world.
