Natural Analogies to Genocide: Invasive Species Displacing Native Equivalents, Which Then Die Off

Very rarely do you spend your time thinking about an invasion of mutant crayfish, but you might, as it provides a potent metaphor:

Every marbled crayfish, known as a marmorkreb in German, is female — and they reproduce by cloning themselves. Frank Lyko, a biologist at the German Cancer Research Center, first heard about the marbled crayfish from a hobbyist aquarium owner, who picked up some “Texas crayfish” at a pet shop in 1995. They were strikingly large, and they laid enormous batches of eggs — hundreds, in a single go. Soon, the New York Times reports, the hobbyist was beset with so many crayfish he was giving them away to his friends. And soon after that, marmorkrebs were showing up in pet stores upon Europe.

There was something very strange about these crayfish. They were all female, and they all laid hundreds of eggs without mating. These eggs, in turn, hatched into hundreds more females — with each one growing up fully able to reproduce by herself. In 2003, scientists sequenced their DNA and confirmed what many owners already believed to be the case: Each baby crayfish was a clone of its mother, and they were filling Europe’s fishtanks at alarming speed. Just 25 years ago, the marbled crayfish did not exist at all. Now, they can be found in the wild by the millions in Germany, the Czech Republic, Hungary, Croatia, the Ukraine, Japan, and Madagascar.

Invasive species, like generalists or people after too much civilization, are simpler and therefore adapt more easily to a new place, at first. Over time their lack of specialization causes them to become more specialized, and they branch off into local species, but first, they have a much easier time of reproducing and displacing any native species that compete with them.

The same is true of government-sponsored immigration. The newcomers have fewer concerns about upholding the civilization and maintaining it, and only need to follow a basic model of feeding and reproducing. Over time, they displace the natives, who then pass into genetic history and are forgotten.

Why Invasive Species Prosper: Less Specific Knowledge, Fewer Enemies

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.