Today I leave for the Davis Mountains to continue my second (and last) field season of thesis research. Last year my adviser was gracious and allowed me the use of his vehicle. This year however, he wasn’t feeling so altruistic. And who can blame him? I had a whole year to arrange for another vehicle.

The problem of course is that I drive a Corolla. She’s light and nimble on her feet and gets a near miraculous amount of miles to the gallon, but she aint exactly renowned for her off road abilities. Her name is Betsy.

I needed more of a bastion of transportation to handle the mountainous terrain. I needed Bertha.

Bertha has a long and storied history. A 1988 GMC suburban that belongs to my parents, she’s like that relative that everyone respects for all they’ve seen and been through, yet no one wants to sit next to at the dinner table because of the smell…

A few years ago in what was expected to be her last hurrah, Bertha embarked with five young gents on a trip deep in the southern bowels of Mexico. She made it all the way to Oaxaca and back. True, she got her gas cap stolen and there were four flat tires in the first six days, but Bertha can hardly be faulted for Mexico’s hooligan youth, shoddy road conditions, and below standard spare tires.

No, Bertha will do quite well for me this summer. She’d better. I just spent $250 to get one of her four windows working (she has no air conditioner) and glue the fabric ceiling back on. She’s just got the right constitution for field work.

I’m really looking forward to these next few weeks. In addition to the research, I’m going to be pulling out the camera in my spare time, catching up on processing all my pictures, and reading lots of books. If my internet connection cooperates, you can expect to see plenty of pictures.

Oh, and by the way, if you’re in the market for a 1988 GMC Suburban with one working window and a glued on ceiling lots of character, I’ll have one for sale in about five weeks.

A new species of hummingbird has just been discovered in the cloud forests of southwestern Colombia. No surprise there. At roughly 1,800 species of birds, Colombia is second to no other country in the total species of birds that it has. Equator + Mountains = ginormous amounts of speciation in lots of different habitat types. With 2,500 species, South America is the bird continent.

Dubbed the Gorgeted Puffleg (Eriocnemis Isabellaea), the bird is quite spectacular.

He’s a puffleg, so he’s got the furry (feathers actually) “disco boots” around his legs. But what struck me the most is that the group of feathers underneath his tail (called the undertail coverts) are iridescent! Lots of hummingbirds have iridescence on their throats, but I can’t recall off the top of my head any that have iridescent undertail coverts. (I’m sure there are plenty in the tropics that I’m just not familar with.)

Despite having so many amazing birds, the article succinctly captures why most birders and even ornithologists don’t usually make it to Colombia.

Investigators caught their first glimpse of the bird while surveying a mountain ridge in the Cauca province in 2005. Braving the zone’s leftist rebels and drug traffickers, they returned to confirm the sighting.

The article also highlights fears that habitat loss from growing drug crops threatens the bird’s existence.

Still, it’s pretty amazing that we’re still discovering new species. There are something like 325 species of hummingbird alone, confined entirely to the new world.

I welcome each and every addition to this group.

I came across a three week old story in the Onion that takes aim at birders, particularly the Sibley Guide. It’s an absolute riot!

Here’s a brief taste, but if you know anything about birding, you’ve got to read the rest of the article.

I don’t understand it. How could it have happened a third time? They’ve had two opportunities to correct it. But there it is, once again. The Sibley Guide To Birds, third printing, page 488: “The dark-eyed junco, a familiar visitor to wintertime bird feeders throughout much of North America, is a species of the junco genus of American finches.”

Mr. Sibley, once again, the dark-eyed junco is not a finch. Its a sparrow. A sparrow.

[…]

Apparently the 42 letters I sent Mr. Sibley, his publisher, and his literary agent either went unread or now line the nests of Carolina wrens. I’m not sure what the mans afraid of, especially since I larded these letters with all kinds of reassurances like “its a common mistake” and “I get all those seed eaters mixed up, too” and other things I didn’t really mean.

And if you’re not laughing, me thinks you need a brief primer on what the Onion is…

Another blogger has used (after getting my permission of course) my recent picture of Burrowing Owls that I put up recently.

Says one of the commenters on the post,

Many thanks for the burrowing-owl photo. It brightened my Monday considerably.

It’s nice to see the shot getting wider exposure.

So I’ve been extremely busy the last few weeks trying to get everything wrapped by the deadlines that always come with the end of the semester. I just completed working on a paper for Molecular Biology about cystic fibrosis. Before I go any further, let me define just a few genetic concepts using the analogy of shoes, so that I don’t have to worry about readers being completely lost. Thirty seconds of biology won’t kill you, I promise.

• allele - alternative version of gene. If shoes are a gene, then cowboy boots, sandals, and tennis shoes would be alleles. For any given gene, you’ve got two alleles - one from mom and one from dad.
• homozygous - you’ve got the same two alleles for a given gene. You’re wearing matching tennis shoes.
  • homozygous dominant - both of your alleles make the same working protein. You’re wearing matching tennis shoes.
  • homozygous recessive - both of your alleles either don’t make a protein or make a protein that doesn’t work. You’re not wearing any shoes and have two bare feet.
• heterozygous - you’ve got different alleles for a given gene. You’re wearing one cowboy boot and one sandal, or one cowboy boot and one bare foot.

Cystic fibrosis is a homozygous recessive trait. You’ve got to get two CF alleles that don’t work right to get the disease.

Enough of the background information. I was focusing on one thing in particular. The allele that causes CF is a lot more common in European populations than one might expect for such a seemingly detrimental allele. In fact in Caucasian populations, the frequency of carriers can reach as high as 1 in 25 people! That’s pretty darn high when you consider that if two copies of those alleles end up in a child, that child’s dead before they’re three years old. How do you explain that? The likely explanation is what’s called heterozygous advantage, where heterozygous are better fit for their environment than homozygotes.

The classic example of this is sickle-cell anemia and malaria. It turns out that heterozygotes are much less likely to get malaria than homozygotes. I was looking on the internet for a reference to the scientific literature that discusses heterozygous advantage with sickle-cell anemia, when I came across this page from the website of a medical doctor at Harvard. (Incidentally, it’s a nice lengthy discussion if you want to learn more about natural selection favoring a detrimental allele through heterozygous advantage.) But it contained one little illustration that immediately caught my eye and made me laugh out loud.

Figure 2. Schematic representation of the effect of the sickle cell hemoglobin gene on survival in endemic malarial areas. People with normal hemoglobin (left of the diagram) are susceptible to death from malaria. People with sickle cell disease (right of the diagram) are susceptible to death from the complications of sickle cell disease. People with sickle cell trait, who have one gene for hemoglobin A and one gene for hemoglobin S, have a greater chance of surviving malaria and do not suffer adverse consequences from the hemoglobin S gene.

Oh, okay. I get it. But still, it’s a rather odd and comical choice for the illustration. It tickled my funny bone so much that I had to share.

So getting back to cystic fibrosis, the main evidence for heterozygous advantage comes from a study1 which showed that the bacteria which cause typhoid fever use the protein that the cystic fibrosis gene creates. Thus, if you’re heterozygous (one good copy, one bad) then you have less of that protein on the surface of your cells lining your digestive tract. Using mice as a model, they showed that typhoid bacteria are 86% less successful at infecting cells of heterozygotes. They also showed that mice containing two bad copies of the CF gene were not infected by any typhoid bacteria. Thus typhoid are using that protein as their entries into the cell.

As typhoid is a disease that has ravaged Europe for many years in premodern time, it now becomes understandable why selection would increase the frequency of the CF allele in European populations.