I’m rearranging the site layout. I like it better already, but more fiddling is possible.
Science blogging, elephantine brains edition
For the week before your midwinter holiday of choice.
- Bacteria can make plastics. (Lab Rat)
- Genes regulating brain development show signs of convergent evolution in humans and elephants. (Ecographica) Which discovery matches nicely with
- A type of neuron once thought unique to great apes has evolved independently in cetaceans and elephants. (Neurocritic)
- Hollow artificial red blood cells could be used in transfusions, or to deliver drugs. (io9)
- Good news: lobsters can check the climate-change-driven spread of the long-spined sea urchin. Bad news: lobsters are delicious. (Conservation Maven)
- Two competing strains of parasites are less damaging to a host than one. (The EEB & flow)
22 January, 2010
That’s when the splendid-looking Charles Darwin biopic Creation finally opens in the U.S. A new trailer is exclusively (?) available over at BeliefNet, of all places.
Cuckholding crows don’t necessarily have healthier chicks
Birds are bad at monogamy. There are a number of good evolutionary reasons to cheat on your mate, and it’s not clear which one is the most likely explanation. A new study of American crows, however, suggests that, for females, cheating isn’t necessarily the best choice [$-a].
Avian infidelity isn’t obvious, because many birds are socially monogamous, forming couples for one or more breeding seasons to raise chicks. However, DNA-based paternity testing has overturned this intuition — a 2002 review of such studies [PDF] estimated that “cheating” occurs in 90% of bird species, and an average of 11% of chicks are “illegitimate.”
The biological term for this non-monogamy is “extrapair copulation,” often abbreviated to EPC. Evolutionary reasons for EPC behavior break down by which parent benefits from the cuckoldry: Females benefit if EPC means their chicks will be less inbred, which can make them less prone to disease or recessive genetic disorders. Males benefit if EPC means they will have more chicks than they would otherwise. Perhaps more importantly, EPC might impose real costs on females, if it leads mated males to invest less in caring for the chicks in their nests because they can’t be sure the chicks are theirs [PDF].
In the new study, Townsend et al. evaluated the costs and benefits of EPC for female American crows, which have a social structure that adds a twist to the cost-benefit analysis. Mated pairs of crows live in larger family groups, which include “auxiliary,” unmated males who may help feed and protect chicks — perhaps especially if those chicks are the result of their own EPC. Females also engaged in EPC with males from outside the family group, who should be less closely related than within-group males, and whose chicks would be more genetically healthy than those sired by any within-group male, mated or not.
Townsend et al. observed several such family groups over four years, using DNA fingerprinting methods to identify the parents of chicks as they were born, and tracking the chicks’ health and survival as well as how frequently mated crows and auxiliary males tended them. Contrary to what might have been expected, chicks produced by EPC were more, not less, inbred; they didn’t grow faster or have a higher probability of survival than chicks produced by mated parents. On the other hand, cuckholded males tended chicks sired by others as often as they did their own.
The most telling result is that broods containing chicks produced by EPC were more frequently tended by auxiliary males — but only when the EPC was with a within-group male. This suggests that EPC mainly benefits male crows, not females. From a mated female’s perspective, EPC produces chicks that are less genetically fit, and no more or less likely to survive, than chicks sired by her mate. On the other hand, an unmated male can only have offspring through EPC, and if he does, it makes sense for him to give them extra assistance. Males from outside the family group don’t stick around to offer that help, but auxiliary males from within the group can, and do.
References
Arnqvist, G., & Kirkpatrick, M. (2005). The evolution of infidelity in socially monogamous passerines: The strength of direct and indirect selection on extrapair copulation behavior in females. The American Naturalist, 165 (s5) DOI: 10.1086/429350
Griffith, S.C., Owens, I.P.F., & Thuman, K.A. (2002). Extrapair paternity in birds: A review of interspecific variation and adaptive function. Molecular Ecology (11), 2195-212 : 10.1046/j.1365-294X.2002.01613.x
Townsend, A., Clark, A., & McGowan, K. (2010). Direct benefits and genetic costs of extrapair paternity for female American Crows (Corvus brachyrhynchos). The American Naturalist, 175 (1) DOI: 10.1086/648553
I’m going to Research Triangle Park!
Specifically, to attend the National Evolutionary Synthesis Center’s ScienceOnline 2010 conference from 14 to 17 January — I learned today that my post on the evolution of human lactase persistence won one of two awards to cover travel expenses to the conference. The other award went to Christie Lynn at Observations of a Nerd, for a great discussion of how environmental change can turn a useful trait into a dangerous one.
The NESCent site has the details and a complete list of entrants, all of which deserve a read. It’s really an honor to have my work selected, and I’m very excited about the conference. And, yes, I’ll blog about it.
In some strange, alternate universe …
David Lynch directed Return of the Jedi. In our universe, he turned down the job when George Lucas offered it to him.
The mind reels. Would the forest moon of Endor have been covered in Douglas firs? Would Luke have had visions of midgets? Would there be vague references to Eastern mysticism, and gruesome exploitation of women? In short … would it have been all that different? Meanwhile, in this universe, someone is probably working on a Jedi–Blue Velvet mashup at this very moment.
Via Kottke.
Joshua tree/moth tees
New at Denim & Tees: a design featuring the two forms of Joshua tree and their pollinators. Coevolutionary divergence, now conveniently flex-printed on fine American Apparel tees.
This week in science blogging
Science blog reading from the interstices of Dead Week:
- The EEB & flow: “Green” product labels break out into categories that parallel competing schools of thought among conservationists.
- Conservation Maven: Birds provide approximately $310/hectare in pest-removal services on coffee plantations.
- Conservation Magazine: A hunting ban in Ontario’s Algonquin Provincial Park has allowed the local wolf population to re-establish its former pack structure.
- Neuroskeptic: Women dosed with testosterone are more likely to treat others fairly than those given a placebo, but less likely to play fair if they think they’ve received testosterone.
- Cognitive Daily: University students’ “gaydar” is as much as 70% accurate.
Picky eating, not genetics, splits leaf beetles
Many different factors can conspire to create reproductive isolation between populations and, ultimately, separate species. Disentangling them is often tricky, but a study recently published in PNAS takes a crack, and demonstrates that two populations of leaf beetles are divided by food preferences, not genetics [$-a]
Neochlamisus larva, and two possible food plants, red maple and willow. Photos by Scott Justis/BugGuide.net, Mary Keim, and John Tann.
Some populations of the leaf beetle Neochlamisus bebbianae eat red maple, and others eat willow; each type grows better on their native host plant. Hybrids between the two species are possible, and they don’t grow as rapidly when raised on either host. This might mean that ecology — adaptation to the different host plants — is creating reproductive isolation between the two forms of Neochlamisus. But it might also mean that the two forms are genetically incompatible.
Many species are separated by intrinsic genetic incompatibility. In these cases, hybrids have reduced fitness, or die outright, because the two species have evolved separately in such a way that mixed genomes cannot produce important proteins correctly. One example was recently found in two lines of the wildflower Arabidopsis thaliana — both lines had duplicate copies of an important gene, and in each line a different copy mutated into non-functionality, so some hybrids between the two lacked any functional copies [$-a].
To differentiate between this kind of genetic incompatibility and ecological isolation, coauthors Egan and Funk conducted not one but two generations of hybridization between maple and willow Neochlamisus populations. In the first (F1) generation, they bred parents from each host-specialized type; but in the second they performed a “backcross,” breeding the F1 hybrids with mates from one or the other of the parental populations.
This produced a population of backcrossed hybrids with 3/4 of their genes from one parental type, and 1/4 from the other. If intrinsic incompatibility separated the types, then these backcrossed hybrids would grow poorly no matter what their host plant. However, if adaptation to separate host plants isolates the types, then backcrossed hybrids would perform better on the host plant of the type with which they shared more genes. This is what Egan and Funk found — backcrossed hybrid larvae grew faster on maple if they shared more genes with maple-type Neochlamisus, and similarly for willow.
References
Bikard, D., Patel, D., Le Mette, C., Giorgi, V., Camilleri, C., Bennett, M., & Loudet, O. (2009). Divergent evolution of duplicate genes leads to genetic incompatibilities within A. thaliana Science, 323 (5914), 623-6 DOI: 10.1126/science.1165917
Egan, S., & Funk, D. (2009). Ecologically dependent postmating isolation between sympatric host forms of Neochlamisus bebbianae leaf beetles Proc. Nat. Acad. Sci. USA, 106 (46), 19426-31 DOI: 10.1073/pnas.0909424106
On my iPod: Too Beautiful to Live
I’m moving back into a labwork-intensive schedule at the moment, which means that I’m burning through podcasts like nobody’s business. Fortunately, I’ve recently been sucked into the orbit of Too Beautiful to Live, the online incarnation of Luke Burbank’s daily talk/music/newsish show. I only found TBTL after it lived up to its its name by getting dropped from the air by Seattle-area radio station KIRO.
Luke and his co-conspirators Jen “Flash” Andrews and Sean DeTorre put together an amalgam of music, pop-culture sound cues, news commentary, and whatever else happens to drift through Luke’s head at the moment of recording. Topics range from the current status of the Large Hadron Collider to Alec Baldwin’s self-esteem issues; one recent episode revolved around plumbing issues in the Burbank residence.* It’s weird and silly and oddly compelling, and it works great in the background while I’m racking pipette tips.**
Which sounds like damning with faint praise, now that I re-read it, but really isn’t. I mean, Studio 360 doesn’t usually make that particular cut. Anyway, you should totally subscribe.
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* The appropriateness of which subject matter was discussed in today’s episode, which was basically a recorded conversation between Luke and his girlfriend on a drive to down to Portland, and which achieved an almost “30 Rock”-grade degree of meta.
** Except for that one occasion when I had to dive across the lab to hit the volume control and kill Jen’s Swedish Chef impression just as my (Swedish) dissertation advisor walked in the door.