DNA barcoding and "15 new bird species:" Not so fast

The popular media and internet have been buzzing recently about the supposed discovery of 15 new species of North American birds based on the DNA barcoding results by Kerr et al (go to Google News for "birds" and "barcoding" for a plethora of articles). To borrow a phrase from our British friends, bollocks. I'm discussing the press reporting about the study here, not the original study itself which takes a much more conservative tone. Simply put, the implication that DNA barcoding is capable of discovering new species all by itself is nonsense. There are two fundamental reasons why this is true.

First, there is much more to speciation than genetic differentiation. The concept of a species is not simply two populations that have not interbred; it is two species that are reproductively isolated by biological means. Genetic distance and species-level distinctions are correlated, but not in an absolute, deterministic sense. Isolating mechanisms and assortative mate choice are critical, and can't be determined just from genetics. You have to actually go out and study real, whole birds, not just their DNA. And in the case of hypothesized species that do not at present overlap in their ranges, you have to look at their life histories and reproductive biology and make your best judgement as to whether they would remain reproductively isolated if they did come into geographic contact. Genetic closeness also does not strictly imply that two entites are the same species, either. Reproductive isolation can be accomplished with only very slight genetic distinctions, and if the two species have only very recently become isolated there might not yet be much total distance between their genomes. Genetic distincitiveness of various populations is only one of many factors considered in splitting and lumping species; indeed, in many ways, it is primarily a marker to tell you that there might be something going on here that needs to be examined in the larger context.

On beyond this, even just within the genetic context, the particular gene being used for the DNA barcoding project is uniquely ill-suited to "discover" closely related, potentially "young" species. Cytochrome C oxidase I is part of the mitochondrial genome. While this gives it many useful characteristics. including a rapid rate of change over time, the salient feature of mitochondrial genes is that they are inherited in an ASEXUAL, purely matrilineal fashion. They are all but useless for investigating rates of gene flow between putative species, which occurs by sexual reproduction. Mitochondrial DNA (mtDNA) does not mix and blend the way the chromosomal genome does. A hybrid does not have hybrid mtDNA. It has 100% of the mtDNA from its mother, and 0% of the mtDNA from its father. In a hybrid zone you will not find intermediate mtDNA genotypes; each individual bird will have the mtDNA from either one species or the other, with no intermediates. As the fundamental, rock bottom genetic consideration when splitting or lumping species is gene flow between the two taxa, mtDNA is a poor tool for assessing this. If you already have the species defined and their mtDNA characterized, then mtDNA barcoding will let you assign any single individual to a species, or at least the species of its maternal line. That is the purpose of DNA barcoding. Discovering "15 new species of North American birds" is not its purpose, nor is it an appropriate use for it. And, I should add, neither is lumping 8 species of "white headed gulls," no matter how much the lariphobes out there would wish it. MtDNA can only suggest these things as possibilities to be investigated further.

There also seems to be a thread in the coverage of this research suggesting that the discovery of "cryptic" species is somehow a news flash. In reality, the uncovering of superficially similar bird species that had been previously lumped has been happening for decades, and genetic taxonomy has been an important part of this process. Back in the 1970's when that bloodbath of an AOU checklist supplement came out, obliterating our juncos, flickers, and many other species, there was also one change that was actually the herald of the future: the split of Traill's Flycatcher into Willow and Alder Flycatchers. Here were two species, differing in vocalizations, breeding biology, and genetics but nearly identical in appearance, finally receiving recognition. This has become a mainstay of the three decades of splitting we have enjoyed since then, from the Western/Clark's Grebe to the Dusky/Sooty Grouse. We can probably look forward to more of these in coming years as well. But these splits have been based on the totality of the species biology, including but not limited to genetic differentiation. The AOU has actually used a conservative approach, and I am sure it will continue to do so. In the future we may well be counting three meadowlarks, three ravens, four screech owls, and two warbling vireos, just as we now count three "solitary" vireos, four sapsuckers, and two sharp-tailed sparrows. But then again, we may not. There's a long way from identifying a difference in the mtDNA genome to determining a species split.

ADDENDUM:

After reading some of the quotes attributed to the study's authors, maybe I'm not so quick to let them off the hook and blame it on the media. Though these quotes are probably over simplified and somewhat out of context, if accurate, they would display a shockingly poor understanding of evolution and speciation. For instance, the quotes suggest unclear understanding of the difference between two populations of one species that have not interbred because of geographic separation, versus two species that do not interbreed because of biologically-based reproductive isolation. And I was downright offended by this quote attributed to Hebert in reference to cryptic species:

They are typically “small brown ground-dwelling shrubbery birds that don’t attract a lot of human attention.”

Um, excuse me? Ornithologists and birders pay no attention to little brown birds? Sorry, gents, but you need to get your heads out of the lab and find out even the tiniest bit about how biology is done in the world of intact organisms before you spout nonsense like this. Library shelves are filled with detailed studies of "“small brown ground-dwelling shrubbery birds."

Money shot

On the fourth morning of staking out the feeder in my mom's front yard the light, bird, birder, optics, and camera all came together simultaneously to yield some good shots of our visiting Common Redpoll. When I first reported the bird nine days ago, Chris Sloan (our regional editor for North American Birds) asked me to be sure and save any pictures I got, no matter how bad, since there were very few photos of redpolls in Tennessee. We've remedied that situation!

Photos taken by me about 10:25 this morning. Click on any for a larger view.







Mike Todd also posted an album of pictures he took last week.

The Daily Redpoll 25 Feb 2007

Mom's Common Redpoll stayed through the weekend, and was quite cooperative today. Around noon, Fred Alsop arrived with a mini-bus-load of ornithology students from East Tennessee State University; all got multiple good looks at the bird before they continued on their long trip home to Johnson City (extreme NW Tennessee, 300+ miles) after a weekend field trip to Reelfoot Lake.

The flat light and my poor optics still didn't allow any high-quality pictures, but I thought these two were kinda cute:





This is my first time hosting (co-hosting, actually; my mother is the real host) a "chase target" like this. Other rarities of this magnitude I have found were in different circumstances and/or didn't stick around nearly so long. It's both thrilling and nerve-wracking; I find myself feeling a bit of personal responsibility for every person who has driven 3 or 4 even 7 hours to see the bird, worrying that it'll be a no-show and they will have wasted a trip! Fortunately, this little critter has been very accomodating, and everytime someone who has been dreaming of this bird for decades finally gets it in his or her binoculars, the world is just a big happy place.

I'd expect the main rush will be over now, with a full 8 days having allowed nearly everyone with the desire and the means to do so a chance to make the chase. I'll be curious to see how much longer the bird stays, with March just around the corner. I'm also hoping for a few more sunny mornings before it goes to try to get that good clear shot to frame and hang on Mom's wall!

Cheeky Redpoll

Something about that little black mask makes this bird look like he has "attitude"...
(photo from Friday, 2/23/07)


Peggy thought this one could pass for an Ivorybill pic:


The light was worse today, so I couldn't get a shot that wasn't motion blurred:
(photo 2/24/07)


In spite of the flat light, good views were had by at least a half dozen early arriving birders, and some other good photos were taken...

L-R: Tommy Edwards (Columbia), Beth Schilling (Knoxville), and Dan Jacobson (Chattanooga). Dan is doubtless phoning Jeff Wilson to boast about TN bird #362.

Redpoll Mania!

At least on a small scale...

Seems Common Redpoll is an even better bird here than I suspected. There's been a steady stream of cars to my mom's driveway from all over Tennessee and much of Alabama, several dozen birders so far. Some have had to wait over 5 hours to see the bird, others have gotten it within seconds, but so far as I know, no one has yet been skunked. Quite a few people who have been birding this area for 30+ years have ticked it as a State or life bird. Tennessee's top ABA lister, Jeff Wilson, added it to his TN tally bringing him up to an astounding 386 species! At least one other of the Tennessee lists topping the elite 350 mark added it as a new tickie as well. Let's hope it stays for the weekend!

Great bird for the Great Backyard Bird Count!

Since this is the weekend of the Great Backyard Bird Count, I decided to drop by my mom's place in town and tally up her yard and feeder birds. After about 15 minutes of watching, I glanced to my right, and not 10 feet from me I spotted this little cutie in a tangle of wisteria:



Common Redpoll! That's a really good bird down here! So I ran home to get my camera, notify the TN-Birds listserve, and make some phone calls. I managed several passable photos through the windows:





First redpoll I've ever seen in the southern States in my many years of birding down here, and I likely wouldn't have found it without the GBBC for incentive.

And now for something completely different?

From a swamp somewhere out in left field:

The Ivory-billed Septic

(No that isn't a typo).

At first glance it looks like just a spoof of Tom Nelson and his band of skeptics, but it turns out to be a spoof on everyone and the whole over-the-top phenomenon. I particularly like the character names, with Clammy Lester a.k.a. Amy Molester and the IBWO-orthotic battling with Implodes and Psychothrush (if these names mean nothing to you, consider yourself lucky). Since it's a parody of everyone, maybe no one will take it too personally?

Catastrophic loss of 18 eastern Whooping Cranes

[Update: As has been reported in the media, one of the birds has been found alive, in the wild, in the company of two Sandhill Cranes]

The entire "Class of 2006" of the eastern Whooping Crane flock was killed in the recent storms in Florida.

Echoes of the past: in 1940, half of the remaining Whooping Cranes in the non-migratory population that once lived on the central Gulf Coast were killed in a single hurricane. This flock never recovered, and the non-migratory race has been extinct for many decades.

Though this is a terrible setback for the eastern Whooping Crane program, it underscores the critical importance of the project. This is a vivid demonstration of why we must avoid having all our cranes (or sparrows or woodpeckers or warblers or orchids or darters or...) in one basket. Establishing multiple populations in widely separated areas is absolutely essential.

That's CHAMPION Psycho Bitch, thank you very much

Ruby the Rhodesian Ridgeback (a.k.a. "Psycho Bitch," especially when in heat or false pregnancy, i.e. about 60% of the time) got her final major win and earned her AKC Championship in Atlanta today. Peggy has been working on this for years, so it's a major accomplishment. Now, depending on how Ruby's health certs go (eyes, thyroid, hips) and how much interest there is in her amongst those better established "in the breed," we may have little Rubykins sometime in the next year. Puppies.. more puppies...