Predators on the move may link the evolution of species thousands of kilometers apart

Can a snake in Thailand influence the evolution of a snake in the Philippines even if the two species never cross paths? According to a new study, the answer may be yes. The research suggests that migratory predators can act as evolutionary “messengers”, carrying their avoidance behavior across continents and linking the fates of species separated by thousands of kilometers. The findings challenge a longstanding assumption in mimicry theory and open the door to a hidden world of long-distance evolutionary relationships connecting distant ecosystems through migration.

To understand how a species evolved, biologists naturally consider factors such as its environment, its evolutionary history, and the species living alongside it. It is easy therefore to overlook the possibility that its evolution may have been affected by a species living thousands of kilometers away. A new study led by PhD. student Akiva Topper, Dr. Yotam Ben-Oren, and Dr. Oren Kolodny of the Hebrew University of Jerusalem challenges a basic intuition in evolutionary biology: that species must live in the same place to co-evolve. Published in the Proceedings of the National Academy of Sciences (PNAS), the research demonstrates how migratory predators can create evolutionary connections between species that never geographically overlap.

The study focuses on mimicry, a phenomenon in which different species evolve similar warning signals, such as colors, patterns, sounds, or behaviors, to deter predators. Traditionally, mimicry has been understood as a local process that requires species to share the same predators in the same place. However, Topper, Ben-Oren and Kolodny propose that migratory predators may carry learned or inherited avoidance behaviors across continents, effectively linking distant species through shared selective pressures.

Using computer simulations, the researchers modeled two geographically separate populations of defended prey connected by migratory predators. Their results demonstrated that predators moving between regions can promote the evolution of shared warning signals even when the prey species themselves never meet.

"Our findings suggest that species do not necessarily have to coexist geographically in order to coevolve," the authors said. "Migratory agents that travel between locations may effectively connect distant ecosystems, allowing evolutionary interactions to occur across large geographic scales."

The simulations suggest that migratory predators may drive the evolution of Müllerian mimicry, where multiple defended species benefit from sharing the same warning signal, across non-overlapping geographic ranges. The study also identified factors that may facilitate or constrain this process, including the strength of local predation pressures and the timing of predator migration relative to the evolution of warning signals.

Beyond mimicry, the authors argue that the same principle may apply to many other forms of coevolution. The paper discusses how migratory species could connect geographically distant plant-herbivore arms races, host-pathogen interactions, and other evolutionary processes that have traditionally been viewed as local phenomena.

"Migration is a major ecological process that moves vast numbers of animals and their effects between distant ecosystems," said the authors. "Our work suggests that it may also play an underappreciated role in shaping evolution across entire continents."

The researchers highlight several real-world systems that may exhibit these long-distance evolutionary connections, including venomous snakes, migratory birds of prey, monarch butterflies and milkweed plants, and viruses spread by migratory hosts and vectors.

The study introduces a broader perspective on evolution, suggesting that species separated by thousands of kilometers may nevertheless influence one another's evolutionary trajectories through shared migratory agents. The authors hope their work will inspire new empirical research into hidden evolutionary connections that transcend traditional geographic boundaries.