For the new work, Cracraft, Barrowclough, and their colleagues at the University of Nebraska, Lincoln, and the University of Washington examined a random sample of 200 bird species through the lens of morphology — the study of the physical characteristics like plumage pattern and color, which can be used to highlight birds with separate evolutionary histories. This method turned up, on average, nearly two different species for each of the 200 birds studied. This suggests that bird biodiversity is severely underestimated, and is likely closer to 18,000 species worldwide.
The researchers also surveyed existing genetic studies of birds, which revealed that there could be upwards of 20,000 species. But because the birds in this body of work were not selected randomly — and, in fact, many were likely chosen for study because they were already thought to have interesting genetic variation — this could be an overestimate. The authors argue that future taxonomy efforts in ornithology should be based on both methods. Paper. (public access) – George F. Barrowclough, Joel Cracraft, John Klicka, Robert M. Zink. How Many Kinds of Birds Are There and Why Does It Matter? PLOS ONE, 2016; 11 (11): e0166307 DOI: 10.1371/journal.pone.0166307More.
But why are the species to be classified only by appearance (taxonomy)? If they can interbreed, how many of them are in fact hybrids? Would we not need genome mapping?
From the Abstract:
Using a sample of 200 species taken from a list of 9159 biological species determined primarily by morphological criteria, we applied a diagnostic, evolutionary species concept to a morphological and distributional data set that resulted in an estimate of 18,043 species of birds worldwide, with a 95% confidence interval of 15,845 to 20,470. In a second, independent analysis, we examined intraspecific genetic data from 437 traditional avian species, finding an average of 2.4 evolutionary units per species, which can be considered proxies for phylogenetic species.
What are “evolutionary units”? Have the species’ ability to hybridize and produce fertile offspring been tested?
One asks because, in general, the concept of speciation is currently a mess:
See also: Mystery species depicted in cave art is buffalo-cattle hybrid?
Cichlid speciation attributed to “plasticity” now
Nothing says “Darwin snob” like indifference to the mess that the entire concept of speciation is in.
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