Molecular phylogenetics: Genetics suggests birds of prey aren’t related

For eons, predatory birds have inspired people across numerous cultures. Religious texts have drawn upon them in metaphors, they have aided hunters in catching game fowl for millennia, America’s founding fathers adopted one as a national symbol, one bird of prey in action adorns the Mexican flag, and various sports teams have chosen them as mascots. While few people may pull over on the side of the road to snap a photo of a chickadee, a bald eagle or California condor would surely elicit excitement and cause people to jump out of their cars to witness their majesty.

Birds of prey, as their colloquial name suggests, appear designed for capturing and disemboweling animals. They tend to have large, and often forward-facing, eyes, which are useful for spotting prey, and their legs are strong and capable of grasping an unwitting animal. Finally, their curved, sharp beaks are excellent for tearing the flesh of their victims. Despite this, not all birds of prey are genetically similar to one another, as you can see in the phylogeny below.

image_3326_2e-Avian-Tree-of-Life

If you scour the figure, you’ll find one genetically distinct group of predatory birds known as Falconiformes, which includes Micrastur, Falco, Ibycter, and Caracara (~2/3 from the bottom of the phylogeny; marked with a small falcon with light blue and red feathers). These include the falcons, falconets, kestrels, and caracaras.

The phylogeny I’m referencing was derived from analyses utilizing 198 bird species with >390,000 letters of DNA [1]. That’s a lot of DNA and a very good sampling of species, so it’s safe to say that most of their results are statistically reliable. What is important to note for my point, however, is that that Falconiformes are genetically similar to things like parrots and perching birds, such as sparrows, crows and finches (all of the species below the falcon-like birds in the figure). Not very predatory species, are they?

Now compare where Falconiformes are in the phylogeny relative to the remaining birds of prey, known as Accipitriformes. You’ll find them at the top of the phylogeny in a separate dark-green box. This group includes eagles, hawks, osprey, kites, and vultures.

So despite their extremely similar anatomy, these groups are not genetically similar to one another. How can this be? One possibility is that their respective lineages independently adapted to a carnivorous diet, thereby adopting very similar features to capture and dismember prey. Another hypothesis, suggested by the scientists who generated the phylogeny above [1], is that many birds descended from a predatory ancestor and Falconiformes and Accipitriformes simply retained these ancestral features.

Regardless of how it happened, the point remains: their genetic similarity does not correspond with their anatomical similarity, a result that is seemingly counterintuitive, yet consistent with evolutionary theory.

Questions for Creationists

Why aren’t all birds of prey most genetically similar to one another? If God created their bodies and the DNA that provides the ‘blueprint’ for their anatomy, shouldn’t their DNA be very similar? Why are falcons more genetically similar to crows, parrots and chickadees?

References

1. Prum, R. O., Berv, J. S., Dornburg, A., Field, D. J., Townsend, J. P., Lemmon, E. M., & Lemmon, A. R. (2015). A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing. Nature.

Photo credit

Phylogeny, crested caracara, Milvago, peregrine falcon, Phillipine eagle, Pacific baza, bearded vulture

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