Uploaded October 2019 | Updated September 2026, 3 weeks ago
New research published in Science reveals that Heliconius butterflies have an unexpected evolutionary history. Rather than resembling a traditional evolutionary "tree," the species' history was more like a bush with many instances of introgression or genetic sharing after speciation.
“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”
In generating 20 whole genome assemblies for Heliconius butterflies, Frandsen and coauthors from Harvard and MIT had the biggest data set they could bring to bear on the situation.
Video produced by BYU University Communications
Producer Julie Walker
Cinematographer Brian Wilcox
Editor Brendan Decicio
Special thanks to the Butterfly Biosphere at Thanksgiving Point in Lehi, Utah.
Release from BYU University Communications (writer Todd Hollingshead):
New butterfly analysis in Science provides resolution for piecing together evolutionary history of species
Colorful Heliconius butterflies have a wide variety of wing patterns and an amazing ability to mimic the look of other butterfly species. They also have an incredible knack for rapid speciation and divergence, which has made them prime research subjects for evolutionary biologists for more than a century.
With all of the things scientists have learned about this dynamic family of butterflies, one burning question still hasn’t been resolved: why do groups of species like Heliconius tend to diversify more rapidly than others? Using a newly pioneered, low-cost sequencing strategy on 20 whole Heliconius genomes, researchers from Harvard, BYU and MIT finally answer the question with certainty.
In a paper published in the Nov. 1, 2019, issue of Science, the researchers pinpoint the rapid speciation of these exceptional butterflies to a phenomenon known as introgression, wherein species exchange genes due to interbreeding between genetically divergent individuals. On a grand scale, the findings provide evidence that the evolutionary tree first concocted by Darwin needs some adjusting.
“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”
When evolutionary biologists want to know about the evolutionary relationships among different species, they generally do that with a tree. Each species is a tip of a tree and a series of bifurcations lead to that tree tip. But it turns out that for many species, there is no resolution as a simple bifurcated tree.
An increasing number of evolutionary scientists have come to believe introgression is at play, especially in cases of rapid speciation. But until now there haven’t been adequate tools to rule out other possible scenarios, such as incomplete lineage sorting events (where two species have a common ancestor with multiple gene variants, but those gene variants don’t perfectly sort with the species boundaries). In generating 20 whole genome assemblies, Frandsen and his fellow authors had the biggest data set they could bring to bear on the situation.
They then came up with a new computational method to determine whether what they were detecting in the genomes was introgression or incomplete lineage sorting. Using BYU’s supercomputing facilities, they found introgression was behind 70 percent of the incongruent genealogies they uncovered in the genomes, as compared to 30 percent for incomplete lineage sorting. This result confirmed that even when speciation events occur close in time, hybridization from introgression is the dominant cause.
New research published in Science reveals that Heliconius butterflies have an unexpected evolutionary history. Rather than resembling a traditional evolutionary "tree," the species' history was more like a bush with many instances of introgression or genetic sharing after speciation.
“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”
In generating 20 whole genome assemblies for Heliconius butterflies, Frandsen and coauthors from Harvard and MIT had the biggest data set they could bring to bear on the situation.
Video produced by BYU University Communications
Producer Julie Walker
Cinematographer Brian Wilcox
Editor Brendan Decicio
Special thanks to the Butterfly Biosphere at Thanksgiving Point in Lehi, Utah.
Release from BYU University Communications (writer Todd Hollingshead):
New butterfly analysis in Science provides resolution for piecing together evolutionary history of species
Colorful Heliconius butterflies have a wide variety of wing patterns and an amazing ability to mimic the look of other butterfly species. They also have an incredible knack for rapid speciation and divergence, which has made them prime research subjects for evolutionary biologists for more than a century.
With all of the things scientists have learned about this dynamic family of butterflies, one burning question still hasn’t been resolved: why do groups of species like Heliconius tend to diversify more rapidly than others? Using a newly pioneered, low-cost sequencing strategy on 20 whole Heliconius genomes, researchers from Harvard, BYU and MIT finally answer the question with certainty.
In a paper published in the Nov. 1, 2019, issue of Science, the researchers pinpoint the rapid speciation of these exceptional butterflies to a phenomenon known as introgression, wherein species exchange genes due to interbreeding between genetically divergent individuals. On a grand scale, the findings provide evidence that the evolutionary tree first concocted by Darwin needs some adjusting.
“The traditional way of looking at evolution as a bifurcated tree doesn’t capture the complexity of the evolutionary process,” said study co-author Paul Frandsen, professor plant and wildlife sciences at BYU. “Instead of a tree, it’s more like a bush or a network. By looking at whole genomes and using our new methods, we can get a much clearer picture of what’s going on.”
When evolutionary biologists want to know about the evolutionary relationships among different species, they generally do that with a tree. Each species is a tip of a tree and a series of bifurcations lead to that tree tip. But it turns out that for many species, there is no resolution as a simple bifurcated tree.
An increasing number of evolutionary scientists have come to believe introgression is at play, especially in cases of rapid speciation. But until now there haven’t been adequate tools to rule out other possible scenarios, such as incomplete lineage sorting events (where two species have a common ancestor with multiple gene variants, but those gene variants don’t perfectly sort with the species boundaries). In generating 20 whole genome assemblies, Frandsen and his fellow authors had the biggest data set they could bring to bear on the situation.
They then came up with a new computational method to determine whether what they were detecting in the genomes was introgression or incomplete lineage sorting. Using BYU’s supercomputing facilities, they found introgression was behind 70 percent of the incongruent genealogies they uncovered in the genomes, as compared to 30 percent for incomplete lineage sorting. This result confirmed that even when speciation events occur close in time, hybridization from introgression is the dominant cause.
