Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification?
A) The two forms interbreed often in nature, and their offspring survive and reproduce well.
B) The two forms live in similar habitats and have similar food requirements.
C) The two forms have many genes in common.
D) The two forms are very similar in appearance.

Question

Quizplus · Accepted Answer

The ability of the two forms to interbreed often in nature and produce viable, fertile offspring is a strong indicator that they are not distinct species but rather variations of the same species, leading to their reclassification as such.

Bird Guides Once Listed the Myrtle Warbler and Audubon's Warbler