4.1 Coevolution of Native Species

Native species are plants, animals, and other organisms that occur naturally in a particular region. In North America, native species are those that were present before European settlement. Native species have evolved together for thousands of years so are adapted to local environmental conditions.

Non-native species, also known as exotic or introduced species, are those that have been brought to a new area from another part of the world. They are often spread by human activities, either intentionally or accidentally. Most non-native species peacefully coexist with the native plants and animals, but since they did not evolve in the region, they may not have the same level of connection to other species within the ecosystem.

Native species have co-evolved, meaning they have developed and adapted in response to each other’s presence. This co-evolution results in intricate relationships that are important in maintaining balanced ecosystems.

Let’s consider a couple of examples of coevolution:

Native Plants and Herbivores

Co-evolution happens frequently with plants and the organisms that eat them, called herbivores. An evolutionary change in the structure of a plant will affect the structure of an herbivore that eats the plant, which in turn affects the evolution of the plant, which affects the evolution of the herbivore… and the cycle continues.

Monarch caterpillars feed exclusively on milkweed because of their co-evolution. As a defence from getting eaten, milkweed evolved toxins called cardenolides that, when ingested, cause organisms to vomit and even lead to cardiac arrest. In turn, monarch caterpillars evolved to resist these toxins. Monarchs even incorporate the toxins into their own bodies, making them poisonous and protecting them from predation (Vernimmen, 2019).

Plants and Pollinators

Co-evolution leads to relationships between plants and pollinators where the morphology of the pollinator depends on the size and shape of the flower it pollinates, and vice versa.

For example, the common blue violet has evolved a flower shape and colour that promotes pollination by bees. Bees can see ultraviolet light, a spectrum invisible to humans. Violets have ultraviolet patterns that guide bees to the nectar and pollen. These patterns can form “nectar guides,” which are like runway markings directing bees to the center of the flower where the reproductive structures are located. In turn, some bees have evolved strong, long tongues that allow them to access nectar deep within the violet’s flowers. This coevolution has caused a mutualistic relationship where both species benefit. The common blue violets get fertilized, leading to higher seed production. And the bees receive a reliable source of nectar and pollen.