Without humans involved, it's not as unlikely as you might think. 2 examples:

The Silversword plant found on Haleakala volcano in Hawaii descends from ancestors found in California, presumably transmitted by birds carrying seeds.

https://en.m.wikipedia.org/wiki/Argyroxiphium_sandwicense_su...

Several separate groups of primates that inadvertently rafted to South America on floating storm debris:

https://www.cnn.com/2020/04/09/world/prehistoric-monkeys-cro...