Hello! I am building a scifi setting, and in this setting there aren't really any known planets besides Earth that would naturally support life (not human life, anyway), but over hundreds of years humans have terraformed several planets to support life in order to build settlements there, and that has included introducing plants and animals from Earth to those planets (my understanding is that terraforming, at least on this sort of degree, isn't really likely to be practical in real life, but that's something I am willing to handwave and go "it works because i say it works, just trust me bro" on).
Once that is done, the wild animals and wild plants brought over to a terraformed planet generally speaking are never transported from one planet to another again, although domestic animals, plants that are farmed, and humans themselves, might be. And I can see insects and microbes getting inadvertently transported from place to place among different kinds of cargo, since they're small enough to escape notice (I mean, the most venomous spider species in my country is a population of spiders that exists in one natural history museum because there were some accidentally brought over in a shipment of stuff from South America in the 60s or so. I can well see that happening on a planetary scale in a scifi story, too - but anyway)
My question is, if you have a population of animals that's isolated from other populations of the species to that degree, how quickly do you start seeing clear differences in the traits that different populations have? Like I don't expect to have entirely different species yet in a matter of centuries, but if you have a population of, say, roe deer, that would have been entirely isolated from other populations for like five hundred years, could there be differences between that population and other populations that a layman might be able to spot?
Tex: If everything’s on the same planet, it’s going to be difficult to truly isolate an area or population, because it’s going to be affected by the same planetary conditions, such as orbit around the nearest star, the ocean and its environment, etc.
Darwin’s finches, for example, have distinct variations in phenotype despite being effectively the same species (a similar situation for the Galapagos tortoises), which shows that a species’ genotypes can still appear as different physical traits given different environmental stresses.
It’s difficult to tell when evolutionary changes occur, because this depends on not only the species, but the environmental changes, the speed of such changes, and how deeply they impact a species in question. There currently isn’t any research being done on evolutionary characteristics of animals and their niche environments that I know of which has already been occurring for a hundred or more years, as much of our current generation of science is relatively recent given the scope of technological evolution.
Taking a look at the niche environment, how it differs from the originating environment (if this is part of the equation), how the two differ, and what environmental pressures are exerted would be a good start in extrapolating how phenotypic expressions might be altered without delving into the much more complex subject of epigenetic changes.
Utuabzu: Gravity, levels of light, the colour of the star, the length of the year and day and the degree of axial tilt are all going to have to be adapted to, since there's not that much that can be done about them. Organisms that evolved seasonal behaviours are going to lose those after a while on a planet with negligible axial tilt and thus negligible seasons. Organisms on tidally locked planets are going to lose traits dependent on a day-night cycle. Organisms on a high-gravity planet will get stockier, while those on a lower gravity one will get taller and thinner.
Photosynthesis is dependent on the interaction of a photosynthetic pigment with certain wavelengths of light. The dominant photosynthetic pigment on Earth is chlorophyll a, which reflects away the wavelengths we call 'green' and absorbs most of the rest of the visible spectrum. One theory for why it's dominant is that because the sun's emissions peak around the green part of the spectrum, this protects the photosynthetic organism from getting burnt - one point in favour of this is that non-chlorophyll a using photosynthesizers tend to favour shade. But around a different star, or even further out in our own solar system, chlorophyll a might not be ideal, and plants that use other proteins would reflect different spectra of light, and thus appear different colours.
But in terms of evolutionary timescale, it depends on generation length. Things evolve based on mutations that offer some benefit to the offspring of the mutant, leading them to be more successful than their peers and have more offspring in turn, which then are also more successful than their peers without the mutation and thus spread it through the genepool. A civilisation that can terraform planets on a reasonable timescale can almost certainly use genetic engineering as a shortcut to ensure their new biosphere can thrive immediately.
So you have a fair bit of leeway in terms of what you can do with other planets' biospheres. Terraforming on a scale shorter than thousands of years would already take technology well beyond anything we have, so you can handwave a fair bit.
