What’s in a Name? How Genome Mapping Can Make It Harder to Tell Species Apart
The biological species concept remains the most widely accepted standard among ornithologists for classification decisions at the species level. But in the last five years, yet another revolution has rocked the world of avian classification. Gone are the days when ornithologists would labor for months to sequence just a few individual genes on their way to building an evolutionary tree. Today’s “high-throughput” or “next-generation” genome sequencing means a student in an evolutionary biology laboratory today can assemble an entire genome—all 1 billion or so units in a bird’s DNA—in just a few weeks.
Birds are apparently a good subject for genome mapping because they have comparatively small genomes.
All of this means that scientists have the ability to peer more deeply into the DNA of birds today than ever before. But in some ways the resulting picture for species classification isn’t getting clearer—rather, it’s getting blurrier. It seems that the more closely evolutionary biologists look into the genome, the more arbitrary the boundaries between some species appear to be. It’s a bit like stepping too close to a pointillist painting: instead of revealing tiny details on the picnickers’ faces, the whole thing dissolves into dots.
Well, if that’s the way it is, what does it mean for specific claims about evolutionary history?
“We didn’t see the kinds of genomic differences that we’d expect to see between birds that have been [reproductively] isolated for long periods of time,” says Taylor.
Instead, says Mason, the world’s three redpoll species seem to be “functioning as members of a single gene pool that wraps around the top of the globe.” Indeed, Hoary, Common, and Lesser Redpolls all have overlapping breeding ranges around the Arctic.
Instead of different genes, the morphological variation—or differences in how various redpolls look—seemed to stem from genetic expression. It’s kind of like how two humans might have the same gene for brown hair, but one person’s hair might be lighter than the other’s—that gene is being expressed differently. In the same way, Hoary and Common Redpolls have remarkably similar sets of genes, but those genes are expressed differently, causing plumage differences. More.
The researchers have proposed that the three groups of birds be treated as a single species.
Why is it taking so long to organize claims about speciation in a manner worthy of science? One possibility is that Darwinism largely depends on convincing people that natural selection acting on random mutation produces the “endless forms most beautiful” that make up the history of life. Any serious effort to reform the classification process would require such a case to be made much more rigorously than it is now. Which means that the few instances we see (as opposed to the many assertions we hear) might diminish further. This would put more pressure on the school textbook industry and for pop science in general to update their thinking as to how evolution works.
Note from Sci-News:
But the evolutionary history of 90 percent of contemporary birds in a group called Neoaves has remained unclear.
The early ancestors of thousands of these species appeared to have evolved suddenly within a few million years after the extinction the non-avian dinosaurs.
Sounds like some interesting projects lie ahead.
See also: Nineteen new “species” of gecko? Or 19 new fundraising opportunities…?
Nothing says “Darwin snob” like indifference to the mess that the entire concept of speciation is in
What the fossils told us in their own words