Why the classic ring species example of the Larus gull is likely a myth

Nature · Published 3 October 2026 Swipe more like this →

In short: The Larus genus of gulls, once thought to be a simple, circumpolar ring species, is far more complex than textbooks suggest. While these birds are iconic, their taxonomy is a moving target, with recent genetic studies challenging long-held beliefs about how these widespread seabirds evolved and interbreed across the globe.

The genus Larus, introduced by Carl Linnaeus in 1758, encompasses a diverse group of medium-to-large seabirds. Historically, this genus acted as a catch-all for most gulls, but modern taxonomy has significantly pruned its ranks. Between 2005 and 2007, researchers determined that the traditional grouping was polyphyletic, necessitating the resurrection of genera like Chroicocephalus and Leucophaeus to accommodate species that did not belong in Larus. This taxonomic instability is particularly evident in the herring and lesser black-backed gull complex, where authorities now debate whether they are looking at two distinct species or as many as eight.

For decades, the circumpolar distribution of these gulls was cited as a textbook example of a ring species. The theory suggested a continuum of interbreeding populations stretching from Great Britain across Northern Europe, through Siberia, and into North America. In this model, the European herring gull and the lesser black-backed gull represent the ends of a chain that meet in Europe without interbreeding. However, recent genetic evidence has dismantled this neat narrative, indicating that the reality of their evolutionary relationships is far more convoluted and likely does not fit the strict definition of a ring species.

The fossil record provides a glimpse into the deep history of these birds, with the earliest accepted Larus fossils dating to the Middle Miocene, roughly 15 to 20 million years ago. Biogeographical data suggests the genus originated in the northern Atlantic before expanding globally during the Pliocene, a period that likely marked the peak of their species diversity. Today, these birds are defined by their stout bills, webbed feet, and a lengthy maturation process, with young birds taking three to five years to acquire adult plumage. While often colloquially called seagulls, the genus remains a dynamic subject of study, constantly reshaped by new genetic insights and the rigorous re-evaluation of ancient fossil specimens.

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