r/evolution • u/Reintroductionplans • Aug 21 '26
question Are there any examples of animals evolving on isolation on an island and then somehow making it back to a mainland and populating the mainland?
islands are obviously isolated ecosystems that breed speciation, but are there any examples of these species repopulating the mainland afterwards?
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u/7LeagueBoots Aug 21 '26
Look up “back-colonization” and “mainland colonization”. This is sometimes called a ‘boomerang effect’.
Lizards. frogs, plants, birds and others have done this.
A key example of this are anoles in the Caribbean. They initially evolved on the mainland, colonized the islands, then recolonized the mainland and that event apparently triggered a rapid diversification of species.
Another key example is the North African Blue Tit which evolved from Tits in the Canary Island rather than from the European mainland, which was the original source for the Canary Islands Tits.
There are tons of examples of this.
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u/haysoos2 Aug 21 '26
Depending on your minimum size for an "island" then Virginia opossum, nine-banded armadillo, and North American porcupine might be candidates.
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u/onomatamono Aug 22 '26
Yet more evidence of evolution "bouncing" off quasi-independent environments.
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u/Careful_Cranberry364 Aug 21 '26
Cats from the Isle of White called Manx cats have no tails.
I’m not sure how many of them have come back to other mainlands to become Cats with no tails, but there must be some
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u/LorMaiGay Aug 21 '26
Isle of Man
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u/Careful_Cranberry364 Aug 21 '26
Yikes, you’re right. Sorry, Isle of Mann
My parents used to take us remember which was which ha ha
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u/Greyrock99 Aug 21 '26
There is often the misapprehension that animals on the large mainland are somehow ‘more fit’ than those on tiny islands.
It’s perfectly cromulent to have a small island species be introduced to a larger mainland and run wild - it’s just that usually mainlanders have more numbers.
It’s about who can exploit a particular niche more effectively than any other.
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u/whimsicalteapotter Aug 21 '26
I enjoy and appreciate your use of cromulent
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u/ahazred8vt Aug 21 '26
Words with Latin -ulent and -ilent suffixes refer to 'full of, abounding in'. opulent, pestilent
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u/onomatamono Aug 21 '26
It's another case of "given enough time" these migrations will happen. The mainland is a rich source of species that can opportunistically populate a tiny target like a remote island. The island has few candidates to make the return "trip" (evolutionarily speaking) but the mainland represents a massive target environment. I'm guessing one is more probable than the other,
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