Domestic animals sometimes become feral animals, and interbreed with compatible wild animals. Conversely, hunters sometimes introduce wild game animals into foreign habitat. These animals sometimes interbreed with compatible native wild species or compatible domestic livestock. Or sometimes exotic pets escape. Or owners dump exotic pets when they become too much of a handful.
To take some concrete examples, wild boar, which were introduced into North America, interbreed with domestic pigs. Lions and tigers sometimes interbreed–producing ligers.
In South Florida, there’s a concern that Burmese pythons may interbreed with African rock pythons. And you also have reticulated pythons in Florida. Dingoes are another example. And Africanized bees.
Or compare feral horse with wild horses.
This raises a question: if an evolutionary biologist were examining the fossil remains of hybrids, how could he tell the difference between a hybrid and an intermediate or transitional species?
Suppose he had fossil remains of lions, tigers, and ligers. In principle, you could have four competing evolutionary trees:
i) Lions evolved from tigers–via ligers
ii) Tigers evolved from lions–via ligers
iii) Ligers evolved from lions and tigers
iv) Ligers were the common ancestor of lions and tigers
How does an evolutionary biologist distinguish evidence for transitional/intermediate species from evidence for hybrids?
Wouldn’t a hybrid share characteristics of two distinct taxa?