Ecosystems are not chaos but a complex dance where every species plays its part. Scientists modeled such a dance: two prey compete for carbon and water (the building blocks of cells), while a predator eats both. Sixteen scenarios emerged — from predator extinction to a steady rhythm for all three species. The most surprising twist: the predator does not destroy but saves the weak by eating its strong competitor. With a gradual change in food, the dance abruptly changes pace — population sizes oscillate like a pendulum.
This choreography explains nature's diversity. Entropy (a measure of disorder) retreats while the predator conducts.
as written by the authors arXiv:2607.13281
Braga and Wardil [J. Phys. A: Math. Theor. 55 (2022) 025601] introduced a population model for two prey species that compete among themselves and are preyed upon by a single predator species. They showed the existence of 16 dynamic scenarios and stated sufficient conditions for the stable coexistence of the three species. The model, which can be seen as replicator dynamics with predator-dependent fitnesses for the prey, is based on two pay-off matrices: one for prey reproduction and one for interaction between prey and predators. We argue that the model can also be seen as a Lotka-Volterra-type predator-prey model with a single prey species, logistic limitation for prey, and frequency-dependent reproduction and capture coefficients. Using this alternative viewpoint, we obtain conditions for the existence of equilibria with the three types of individuals. We also prove theorems on the stability or instability of equilibria with only two species and relate the stability change of these equilibria to the appearance or disappearance of equilibria with the three species. When all parameters, except the one that regulates carrying capacities, are fixed, a rich cascade of bifurcations may appear. Solutions range from predator extinction due to insufficient prey to predators coexisting with one or two prey types. Sometimes stable limit cycles involving all species appear.
Real ecosystems often hinge on 'keystone' predators: for instance, starfish eat mussels and prevent them from taking over all the space, freeing up room for other inhabitants.