The scrub jays of Santa Cruz Island really love a good peanut.

March 12, 2015 6:04 PM

This Jay Is Evolving in a Very, Very Weird Way. As she gathered more and more data on different populations of the island scrub jays around Santa Cruz Island, Katie Langin, a biologist at Colorado State University, had a revelation: The birds, members of one single species, had split into two varieties in different habitats. Ever since Darwin and his famous finches, biologists have thought that in order for a species to diverge into two new species, the two populations had to be physically isolated. Those finches, for instance, each live on a different Galapagos island, where their special circumstances have resulted in specialized bill shapes. Yet the two varieties of island scrub jay (they haven’t technically speciated—yet) live on the same tiny island. If they wanted to meet each other for a brunch of acorns and/or pine nuts and perhaps later some mating, they could just fly right over.

Now, the island scrub jay has apparently said “screw all that isolation.” This is particularly weird because birds have, you know, wings. It’d be easy to see how something less mobile like a snail could split and stay isolated, but the jays are more than capable of flying between populations and mating. Yet they only very rarely do. Why that is, Langin isn’t yet sure, but she has a few hypotheses. A simple explanation would be that each variety is only attracted to birds with beaks like its own. But then how did the split happen in the first place? Perhaps a population of jays long ago settled in a certain kind of forest, evolved either an acorn- or pine cone-specialized beak, and henceforth found only that trait to be wildly attractive (sexual selection is, after all, a matter of determining the fitness of your mate, and few things are more fit than being able to eat the food in your environment). “Another alternate hypothesis going into this would be maybe individuals that are hatched in pine habitat just prefer to settle in pine habitat,” Langin says. “There’s actually a lot of evidence that experiences birds have immediately after they hatch come into play when they’re selecting a place where they want to breed.” She cautions, though, that her study didn’t collect the data needed to support this, and that more research is in order here.

Langin's study in Evolution, "Islands within an island: Repeated adaptive divergence in a single population."

via the Corvid Blog.

posted by jaguar (11 comments total)

Yay, a bird post!

We put up a fat pack for our bird feeder last year, and the western scrub jays would come and YELL ALL THE TIME.

First they'd sit in one of our trees. HEY HERE I AM. LOOK AT ME!

Then they'd jump on the fence. YEP. STILL HERE. HOW 'BOUT THAT?

Then they would alight on the top of the feeder. WOO BABY. LOOK AT THAT FAT PACK!

Then they'd jump to the fat pack and start feeding. stab stab stab stab

Then they'd fly back to the fence, but not before cleaning their beaks on the metal of the bird feeder. WOW THAT WAS GREAT. AND I AM AWESOME.

But we had to cut down the trees (they were quite dead and leaning against the power lines) and the jays have not been back. There is a tree a couple of feet away in the neighbor's garden, but I guess it's not close enough, and they feel too exposed. :(
posted by potsmokinghippieoverlord at 6:32 PM on March 12, 2015 [3 favorites]

"Ever since Darwin and his famous finches, biologists have thought that in order for a species to diverge into two new species, the two populations had to be physically isolated."

Er, no they haven't. Sympatric speciation was first proposed not too long after Darwin (early 1900's IIRC), and others like Mayr & Smith pretty much formalised it from the 40's onwards. At most, the arguments against boil down to an argument of "absent of geographical isolation, is behavioural / reproductive isolation a special case of physical isolation?"
posted by Pinback at 6:48 PM on March 12, 2015 [5 favorites]

Snail chirality also seems to be able to cause speciation. Clockwise-snails and widdershins-snails just can't get it on.
posted by Leon at 7:04 PM on March 12, 2015 [2 favorites]

Er, no they haven't.

I suspected the article may have been overstating the case, especially since it mentions other similar cases. It's still rather neat to see such a small population in such a restricted geographically area differentiate to such an extent.
posted by jaguar at 7:05 PM on March 12, 2015

I love scrub jays. They are my best friends. I pay them for it in peanuts.
posted by annathea at 7:09 PM on March 12, 2015 [2 favorites]

That's a handsome bird, but not a trustworthy bird.
posted by the uncomplicated soups of my childhood at 7:14 PM on March 12, 2015

What if only some of them aren't repulsed by pine nuts, or the others by acorns--like, on a genetic level, like the way some people can't taste the soapiness of cilantro?
posted by Sys Rq at 10:39 PM on March 12, 2015

That may not appear to be something you’d consider a “revelation,” but it really is—if you believe in evolution. [emphasis added]

Sigh. If we have to tolerate this type of wishy-washy, faux-balance, "we can't offend the fundies!" equivocating from even the (supposedly) science/tech oriented magazines than we are truly fucked.
posted by dry white toast at 5:32 AM on March 13, 2015

Fortunately, you don't have to believe in evolution for it to be true.
posted by Dashy at 7:24 AM on March 13, 2015 [2 favorites]

Er, no they haven't. Sympatric speciation was first proposed not too long after Darwin (early 1900's IIRC), and others like Mayr & Smith pretty much formalised it from the 40's onwards. At most, the arguments against boil down to an argument of "absent of geographical isolation, is behavioural / reproductive isolation a special case of physical isolation?"

That said, while the theory of sympatric speciation has been formalized in the literature for a while, there has been a lot of experimental debate about whether it ever exists in nature. For example, the best-studied example of sympatric speciation is in Rhagoletis pomonella, the hawthorn fly. In the past century, when humans brought apples to North America, lineages of R. pomonella began laying eggs on apple fruits as well as haw fruits. These lineages began to specialize on apples exclusively, such that apple R. pomonella preferentially mate only with other apple flies and haw flies now preferentially mate only with haw flies. There's some cool studies on how their sensory systems have diverged over time to make them attracted or repelled to different components of the scent of apples and haw, and plenty of neat stuff about them.

The trick with that, theoretically, is that hawthorn fruits and apple fruits present different microhabitats. So while they certainly live in the same overall ranges--haw flies and apple flies have plenty of opportunities to encounter each other as they disperse to new trees--they actually lay eggs and mostly breed on the fruits. You will therefore find people arguing that this is really an example of peripatric speciation instead, which is another concept popularized by Mayr.

(There is a lot of argument still around today regarding sympatric speciation, is my point. It's not a new concept at all, but it's still a surprisingly controversial one. That said, personally I think a lot of the criticism is goalpost moving, but that's beside the point of "is it really cool to find an example of sympatric speciation in the wild?")
posted by sciatrix at 7:30 AM on March 13, 2015 [6 favorites]

I would care more if I didn't spend a year in a house where there was a scrub jay sunrise welcoming party in the shrub right outside my window every morning.
posted by Badgermann at 8:46 AM on March 13, 2015