Quote:
Originally Posted by thrash
Note that the reverse can also be true, leading to anything from an "Australian rabbit problem" to a gray-goo scenario where Earth-derived microbes out-compete the local ecosystem's defenses.
It might be interesting to have three different outcomes: one world (younger or less competitive than Earth) where invasive species are ruining the ecosystem, one (older or more competitive) where Earth species struggle to survive, and one where the contest is on more or less equal terms.
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Earth species need a sizable advantage to be able to take over. As introduced species, their numbers will naturally be much lower than those of established ones, making it harder to establish a foothold and start taking over. From what I understand, rabbits in Australia, despite the advantages they had being quick-breeding, placental mammals for whom Australia was a near-optimal habitat, couldn't really establish themselves in the wilds until a) the native predators who had decided rabbits were
delicious had been hunted more-or-less to extinction and b) a particularly-well-adapted breed was accidentally introduced (the fellow involved wanted all of a particular type of rabbit, but the one sending could find enough of that type and sent another breed as well; the interbreeding of the two lines exhibited remarkable hybrid vigor, and all the rabbits in Australia today are descended from them). Other places where introduced species tend to take over I believe typically lack predators (so a predator species rapidly rises to the top of a population not equipped to deal with them, while a prey species who evolved to have extra offspring to account for predation outbreeds the natives in absence of said predation), or you have the humans overhunting said predators.
That said, I opted (largely for simplicity, as I have no desire to create unique biomes for each planet) in my Harpyias setting to have Earth life completely take over the colonized planets, on account of lifeforms there being rather simple (roughly pre-Cambrian). I got the idea from the
Freefall webcomic (where one of the main characters is from a world where the lifeforms are functionally "less-evolved," and he notes just about any Earth organism would rapidly take over; also, basically everything from Earth finds his species to be delicious), but the webserial
Deathworlders takes a similar approach with the planet Cimbrean. In both cases, Earth life has a
massive advantage over the natives.