A new study on the genomes of reeds gives us an insight into what gives invasive species an upper hand over native ones:

“Smaller genomes are more nimble,” she said. “They can grow in variable environments and at almost all latitudes.” The findings of the research team raise the question of why plants with small genomes are more likely to become invasive. She thinks they have the answer. “The main theoretical reason has to do with minimum generation time,” she explained. “The idea is that a smaller genome can be replicated more quickly than a larger genome. So if a plant is in a stressful environment, it can be replicated more quickly than if it had a larger genome. It needs fewer resources and can use its resources quickly to reproduce before its luck runs out. “On the other hand, a smaller genome also means that it may lose genes that are potentially beneficial,” added Pyšek, the first author of the paper. “So there may be a trade-off.”

Smaller genomes means fewer instructions, which means a generalist — “can grow in variable environments and at almost all latitudes” — with fewer genes coded to specific adaptations such as would anchor a plant in one environment. This generalist status means that the plant has a lower burden of fitting into an ecosystem and therefore, more energy to reproduce, and a simpler form to reproduce as well.

As time goes on, such plants become adapted because the ones that develop specific adaptations become more efficient. They therefore have more energy than their less-specialized cousins, and gradually genetically predominate. The same will be true of invasive animals, including humans. The ones that are least adapted to their specific country of origin, and therefore most generalized and simplest, will arrive in new lands and out-reproduce the natives, displacing them and eventually, genetically absorbing them.

In effect, this is a “race to the bottom” where simpler species constantly overwhelm and destroy more complex ones, unless the environment is hostile enough that generalists do not thrive in it because they lack the specific adaptations.

Invasive species have another advantage, which is that they lack the predators and enemies that they had back in their homelands, while invasive species must contend with such others, meaning that all of the energy which would have to go to defending the invasive species can instead be invested in reproduction:

“Our native Phragmites in North America is getting hammered by both native and introduced insects, whereas the invasive Phragmites in North America suffers far less herbivory than it does in its native Europe,” she said. “That’s partly because when invasives are introduced to a new place, they leave their enemies behind and can devote their resources to greater growth.”

The same applies to immigration. People of simpler genomes, with fewer specific adaptations, can abandon their enemies at home and gain an easy foothold abroad. At that point, the only thing that holds them back is xenophobic elitism on the part of the natives, who will recognize assimilation in progress and resist it, at least if not restrained by government and media.