Long believed to be a single, globally distributed species drifting freely across the open ocean, the bluebottle – also known as the Portuguese man o’ war – has been revealed to be a group of at least four distinct species, each with its own unique morphology, genetics, and distribution.
Uncovered by an international research team led by scientists at Yale University, the University of New South Wales, and Griffith University, the genetic discovery is being heralded as something of a revelation to the marine biology community.
It was made when researchers began sequencing the genomes of 151 Physalia specimens from around the world. Now published in the journal Current Biology it found “strong evidence of reproductive isolation” among five genetic lineages.
“The genetic data clearly show they’re not only different, they’re not even interbreeding despite overlapping ranges,” said Professor Kylie Pitt, a professor at Griffiths University.
The bluebottle is uniquely suited to long-distance travel, using its gas-filled float and muscular crest to catch the wind and sail the sea surface. Using an integrative approach, the team matched genomic lineages with four distinct physical forms identified from thousands of citizen-science images submitted to iNaturalist.org.
Interestingly, this isn’t the first time the suggestion that the bluebottle was in fact four morphological separate species has been made. The idea was originally proposed in the 18th century and again in the 19th century but dismissed each time.
Using today’s advances in science, however, the suggestions have indeed been verified by modern genomic evidence.