How “invasive species” are *forever* (it seems) invasive?

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My thought process is that, after enough time, an invasive species of some plant or animal would find its way into its new ecosystem, and properly become a part of the ecological cycle? Does this ever happen? Maybe it just needs far more time to do so?

In: Biology

12 Answers

Anonymous 0 Comments

You have to think about the span of time that evolution occurs. Evasive species have been around for as long as humans have been crossing oceans, which is only a few centuries.

Evolution happens over tens of thousands to millions of years. The problem with an evasive species is they evolved in a completely different ecosystem so the normal back and forth of species evolving in the food chain is interrupted. Most would-be evasive species are ill-equipped for the environment they are brought to an die off immediately. The evasive species we know of are the rare anomalies whose traits allow them to outcompete outcompete other predators and decimate the food chain. It’s possible that over tens of thousands of years, the ecosystem would adapt to these species but in other cases, the change is so abrupt that the evasive species effectively wipes out the ecosystem. Again, this has occurred over the course of decades or centuries. Meaningful evolution generally takes millennia.

Anonymous 0 Comments

The problem is twofold:

“Enough time” is potentially thousands of years, depending on the species comp already there and how quickly they’re able to adapt

Invasive, sort of by definition, are aggressive and highly competitive. To the point where they will tend to outcompete more laid back natives trying to fill the same niche. It may seem like this wouldn’t matter (the niche is still filled, after all. What’s the practical difference?) But this can cause two major problems: 1. Trophic cascades. Every other species that interacts with that niche is adapted to the old species. The switch may well have negative impacts on other species, and this can lead to large chunks of local ecology completely collapsing and the entire system failling. 2. It leads to a drop in biodiversity. In general, a more biodiverse system is more robust and better able to respond to changing conditions.