Are Wagtail subspecies supported by genetic data?

A phylogenetic perspective on the relationships between Wagtail species and subspecies.

Ornithologists love to delineate subspecies. One differently colored feather can already trigger a response in the most extreme splitters. But are subspecific divisions always supported by genetic data? Rebecca Harris and her colleagues test this idea for a bird group that has its fair share of subspecies: the Wagtails (genus Motacilla). The paper was published in Molecular Phylogenetics and Evolution.

Some Subspecies

There are 12 species of Wagtails, distributed across the Old World. Two species complexes have fallen prey to subspecific splitters: the Western Yellow Wagtail (M. flava) consists of 13 subspecies, while the White Wagtail (M. alba) “only” comprises 9 subspecies. Some time ago I wrote about hybridization between two White Wagtail subspecies (alba and personata, read all about it here).

An overview of the subspecies in White Wagtail (left) and Yellow…