Question

What happened to the greenish warbler birds as they migrated from the southern portion of their range up around the Tibetan Plateau? What are two main distinctions between the East Siberian greenish warbler and the West Siberian greenish warbler

Answer 1

1. Answer;

They evolved separately as they moved north and became two separate species.

Explanation;

The greenish warblers weren't geographically isolated, but they migrated around the Tibetan Plateau, evolving separately until they were no longer able to interbreed when both species (East and West) contacted in Siberia.

Greenish warblers were thought to have evolved from a single ancestral population that gradually diverged into two new species as it expanded northwards around the Tibetan plateau.

2. Answer;

• Their plumage patterns.
• Genetics and history

Explanation;

West Siberian greenish warblers (P. t. viridanus) and east Siberian greenish warblers (P. t. plumbeitarsus) differ subtly in their plumage patterns, most notably in their wing bars, which are used in communication. While viridanus has a single wing bar, plumbeitarsus has two. Around the southern side of the ring, plumage patterns change gradually.

Additionally, the  two northern forms viridanus and plumbeitarsus are highly distinct genetically, but there is a gradient in genetic characteristics through the southern ring of populations. The greenish warblers were once confined to the southern portion of their range and then expanded northward along two pathways, evolving differences as they moved north. When the two expanding fronts met in central Siberia, they were different enough that they do not interbreed.

Answer 2

The greenish warbler migrates from the Tibetan Plateau to India every year. During their migration, two species of greenish warblers met up, but didn't interbreed, therefore these birds are still two separate species. Because these birds are so closely related, it is rare that interbreeding didn't occur.