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  • July 27, 2010
  • 09:05 AM

Before they were yucca moths

by Jeremy Yoder in Denim and Tweed

Yuccas and yucca moths have one of the most peculiar pollination relationships known to science. The moths are the only pollinators of yuccas, carrying pollen from flower to flower in specialized mouthparts and actively tamping it into the tip of the pistil. Before she pollinates, though, each moth lays eggs in the flower—the developing yucca seeds will be the only thing her offspring eat. How does such a specialized, co-adapted interaction evolve in the first place? My coauthors and I attempted to answer this question in a paper just published in the Biological Journal of the Linnean Society, by reconstructing the ecology of yucca moths before they were yucca moths [PDF].

Using the present to reconstruct the past

Before I describe our study's results, let me explain a little about how biologists can reconstruct the characteristics of extinct species using what we know about living ones. First, we use DNA data to reconstruct evolutionary relationships between our favorite living species—this gives us an evolutionary tree, or phylogeny, like the ones in the illustration below. A phylogeny diagrams the branching evolutionary history that led to the living species at the tips of the tree. If we map the different states of some character that all those species have—say, the color of their feathers, onto the tips, we can infer what the ancestors at each of the inner branch points might have been like.

For instance, consider the possible scenarios for species A, B, C, and D in the illustration below. In the first case, if A and B are both red, then their common ancestor was probably red, too. However, C is blue—what does that mean for the common ancestor of C, A, and B? Because D is blue, we infer that the common ancestor of C, A, and B was also blue, as was the common ancestor of all four species. This is the most parsimonious reconstruction—it minimizes the number of times that color changes in the evolutionary history of the four species.
.flickr-photo { }.flickr-framewide { float: right; text-align: left; margin-left: 15px; margin-bottom: 15px; width:100%;}.flickr-caption { font-size: 0.8em; margin-top: 0px; } Knowing evolutionary relationships between living species helps us estimate the characteristics of their ancestors. Image by jby.In the second scenario, species D is red, so the same logic infers that the common ancestor of A, B, and C was red. In the third scenario, adding another red species (E) to the tree might also alter the most likely character states for the ancestral species on the tree—but this depends on where the DNA suggests that the new species fits on the tree. Most modern reconstructions of ancestral character states are more statistically complex than what I've just described, but the underlying logic is the same.

What did the ancestors of yucca moths do for a living?

.flickr-photo { }.flickr-frameright { float: right; text-align: left; margin-left: 15px; margin-bottom: 15px; width:40%;}.flickr-caption { font-size: 0.8em; margin-top: 0px; }
A small sample of Prodoxid diversity: Greya politella (above) and Tegeticula synthetica (below). Photos by jby.So in order to reconstruct what yucca moths were like before they became yucca moths, we need to know the evolutionary relationships between yucca moths and their close relatives, the other members of the moth family Prodoxidae. This is a diverse group, including The yucca-pollinating genera Tegeticula and Parategeticula;
The genus Prodoxus, moths that lay eggs on various parts of yuccas (and other related plants) without pollinating them;
The genus Mesepiola, which lay eggs on the flowers of plants similar to yuccas—woody desert monocots;
The genus Greya, which lay eggs in the flowers of a number of different plants, and pollinates some in the process [PDF]; and
The genus Lampronia, which lay eggs in another wide assortment of plants.
This diversity offers some intriguing possibilities—depending on how these genera are related to each other, the moths that would colonize yuccas and evolve obligate pollination mutualism might have lived on anything from roses to saxifrages, and their larvae might have eaten leaf tissue, woody twigs, fruit, or flowers. However, the last study to reconstruct the evolutionary relationships among these groups included only one species of Lampronia, leaving a number of current host plant associations and larval feeding habits unrepresented.

So we collected new DNA sequences from another dozen species in the genus Lampronia, reconstructed their relationships to the rest of the Prodoxidae, and used the resulting phylogeny to estimate the host plant association and larval feeding habit of the ancestral species that gave rise to the yucca moths. The results are presented in the large, color-coded figure below. Interpretation of this figure is similar to the example I gave above, except that the reconstruction method we used allows us to estimate the relative probability of each character state at the ancestral nodes, which we present in color-coded pie charts.

This gives us a better picture of the evolutionary changes in the lineage that would become yucca moths. The ancestral moths probably fed inside floral ovaries all the way back to the origin of the Prodoxidae. Before colonizing woody monocots (the Agavaceae, the family including yuccas, and possibly the Ruscaceae, the family fed on by Mesepiola), they most likely fed on plants in the rose family.
.flickr-photo { }.flickr-framewide { float: right; text-align: left; margin-left: 15px; margin-bottom: 15px; width:100%;}.flickr-caption { font-size: 0.8em; margin-top: 0px; }
A simplified phylogeny of the Prodoxidae, with reconstructions of ancestral host plant associations (by family) and larval feeding habits. Image from Yoder et al., Figure 2.This reconstruction gives us the best picture we've had to date of the conditions under which yucca moths evolved obligate mutualism—before they were active pollinators, the moths were already feeding inside developing flowers. This suggests that active pollination evolved to help ensure a larval food supply. We might imagine, then, that plants used by these pollinating seed parasites would evolve greater dependence on their highly efficient pollen delivery, moving toward the yucca-yucca moth mutualism we see today.


Brown, J., Leebens-Mack, J., Thompson, J., Pellmyr, O., & Harrison, R. (1997). Phylogeography and host association in a poll... Read more »

  • July 27, 2010
  • 08:00 AM

North American crayfish diversity threatened

by Zen Faulkes in Marmorkrebs

When I recently attended the International Association of Astacology meeting, it was ground into my face how bad things are for crayfish.

In Europe, crayfish are being beaten up by exotic North American species. If competition doesn’t get them, the crayfish plague that the exotics carry will.

In North America, the home to the greatest diversity of crayfish species in the world, non-indigenous species are playing a role in some regions, but habitat degradation is the bigger concern. At the Astacology meeting, we were treated to scenes like this:

Mountains are being flattened to remove coal.

Strangely, the same factors that lead to the wonderful high diversity of North American crayfish are the same factors that make them vulnerable, mainly geographic isolation. Because crayfish need to stay wet, and are not terribly mobile, they often don’t disperse very well on their own. Consequently, many species have a limited range, often falling within a few locations in a single American state.

Taylor and colleagues provide a summary of just how bad things are in North America. The take home message that every crayfish biologist and every crayfish pet owner should have burned into their brain is this:

Almost half of North American crayfish species are under threat.

I don’t use the phrase “under threat” in any sort of technical way, but just indicating some sort of conservation concern.

On a per species basis, crayfish are the second most threatened kind of animal in North America, behind freshwater mussels, which obviously have many of the same issues as crayfish: small geographic ranges, limited mobility, vulnerable to competition and habitat degradation.

Taylor and colleagues provide other useful information, including a list of all known species and a standard common name. The article is rather nicely illustrated with a few crayfish pictures, too (not for every species, however).

All of this makes the prospect of Marmorkrebs being introduced into North American waters a veritable nightmare scenario. Competition between Marmorkrebs and a local species could be enough to push a species into extinction.


Taylor, C., Schuster, G., Cooper, J., DiStefano, R., Eversole, A., Hamr, P., Hobbs, III, H., Robison, H., Skelton, C., & Thoma, R. (2007). A Reassessment of the Conservation Status of Crayfishes of the United States and Canada after 10+ Years of Increased Awareness Fisheries 32(8): 372-389. DOI: 10.1577/1548-8446(2007)32[372:AROTCS]2.0.CO;2

Photo by ddimick on Flickr. Used under a Creative Commons license.... Read more »

  • July 27, 2010
  • 08:00 AM

Do octopuses play?

by Mike Mike in Cephalove

         I was recently pointed to this article on "octopus intelligence".  I like the article (which features quotes from such cephalopod research all-stars as Roger Hanlon and Jennifer Mather,) although I am a bit let down by the brief, incomplete explanation that is given to the various "intellectual" abilities of the octopus such as "problem solving" and "play".  Both of these behaviors are difficult to define precisely, and are often understood in vertebrates by analogy to human experience.  For example, one of the criteria that is used to define play in animals (as stated in Kuba et al. 2003, a study on play-like behavior in octopuses) is that it is "spontaneous and pleasurable ('done for its own sake')".  This is one of the central features of play - that it appears to serve no other immediate purpose than to entertain or occupy the animal expressing the behavior.  I take some issue with the use of the term "play to describe octopus behavior, at the very least because the implications of play-like behavior in the octopus are not very well studied yet.  It's much harder to determine the motivational significance of an activity in an octopus than it is in, say, a rat.  This is because we know the brain and behavior of the rat much more thoroughly than we know those of octopuses, and since they are structurally similar to ours we can relatively easily design valid measures of motivation in rats.  In contrast to the vast (though still incomplete) neurological and behavioral description of pleasurable and aversive states in the rat that we have generated, we have only a very crude measure of the possible hedonic characteristics of an activity in the octopus; that is, we can assume that the octopus will do "pleasurable" things and will avoid aversive things, but we have little more to go on when we are talking about the motivation of an octopus.  Because of this limitation, I think that it may be too early to say for sure what processes play-like behaviors in the octopus actually represent, and so the touting of play as evidence of the impressive mental powers of the octopus also seems premature.         Whoa, now!  Before I go making assertions like this, I should look at the research, right?  Good call.  Let's see what the vast scientific library that is the internet can teach us about the play-like behavior of octopuses.         I'll focus on Kuba et al. (2006), a recent study that was done to examine putative play behavior in O. vulgaris.  In this study, the authors exposed octopuses to stimuli made out of Lego blocks for half an hour at a time repeatedly over a period of 7 days and scored the octopuses reactions to the objects.  The authors' scoring system is illustrated below (this if Figure 1 from the paper.)         As you can see, level 3 (which the authors describe as "play-like") and level 4 (which the authors call "play") involve repeatedly manipulating non-food objects in complex, non-stereotyped ways for a significant amount of time.  Out of 14 (wild-caught) subjects, object manipulation that was scored at level 3 was observed in 9 subjects, and object manipulation that was scored at level 4 was observed in one subject.  There was no difference of age or hunger state in this behavior (young and old octopuses showed the same sorts of behavior, as did hungry and sated octopuses.)  Play-like behaviors tended to occur after several days of presentation of the stimulus, suggesting that this was not merely exploratory behavior, which appeared to decrease during the first few days of exposure (as the octopuses presumably got used to the presence of the stimuli in their tanks.)         By this point, I tentatively buy the characterization of these behaviors as "play" - they don't appear to serve any purpose for the octopus, who is clearly not simply confusing the objects with food.  They are exhibited after the octopus has presumably had ample time to learn that they do not represent a threat.  The behaviors do not appear to clearly belong to any other class of behavior (except perhaps tactile exploratory behavior.)  As I said before, however, using the existence of these behaviors to argue for the intelligence of the octopus seems premature to me.  For one, the significance of these behaviors in the wild is not well understood - they must confer some survival utility, but they do not appear to be disproportionately expressed in young, rapidly developing octopuses as they are in mammalian young, and so are unlikely to contribute to neurodevelopment in the same way that play in mammals (especially social mammals) is thought to.  We know that play in social mammals (like humans, some apes, and rats) serves a variety of functions in development - to establish dominance hierarchies, to develop skills for living within social organizations, to learn hunting and food-gathering behaviors, to help develop motor coordination, etc.  We have comparatively little sense of the importance of play in the life of an octopus, and so it is hard to know what play-like behavior means in the context of octopus cognition.         Because we know that play is very important to the cognitive function of mammals I mentioned previously (more properly, we know that disrupting play behavior causes deficits in behaviors that depend on play to develop,) we can claim that play is part of a group of behaviors that make manifest the intelligence of these animals.  Without knowing what play-like behavior does for an octopus, it's hard to say whether it implies an analogous intelligence in these animals.  It might be explained in many cases as a simple extension of exploratory behavior.  As a foraging predator, it makes sense that O. vulgaris would be served well by repeated, thorough explorations of the same object, which mobile and semi-mobile prey would presumably periodically be found on.  This behavior might be explained as part of a foraging strategy that is somewhat impervious to associative learning, and so violate the criteria that we use to classify a behavior as play all together.         My discussion thus far has accepted the hypothesis that behavior classifiable as play occurs regularly in the octopus, and thus needs to be explained in terms of its adaptive utility to the animal.  Based on the previously summarized paper, however, clear play-like behavior in the octopus appears to be pretty rare.  On the 5th day of the experiment, when play-like behavior peaked, 444 interactions with the stimuli were observed.  Out of these, 13% qualified as level 2 (they involved manipulation beyond very basic exploration of the object with the arms,) 0.9% were scored as play-like, and a single observation (0.02% of the total observations) was scored as being definitively "play".  I think this was a well-designed study, but the results don't convince me that play (as defined by the authors) is terribly important in the lives of octopuses, and might just as well represent a rare, specific type of interaction that they have with unusual stimuli in a laboratory environment.          I realize that I have been sort of hard on this study.  I don't want to imply that octopuses are not remarkable animals that are capable of many things one wouldn't expect from a mollusc.  I do think, however, that it pays to be very skeptical about the use of the terms "play" and "intelligence".  Both of these are concepts that we understand primarily by analogy to our experience of them as humans.  We know that social play in vertebrates is indeed play (even the scientists among us) because we know what a play fight feels like, and understand intuitively how it differs from a real fight.  We can extend this to behaviors that we see in animals (with more or less accuracy, depending on the situation.)  We know what intelligence means (or we think we do) because we have expectations of how people should function, and we can draw analogies to other vertebrates who have the same sort of behavioral flexibility and environmental demands that we do.  One might dismiss this as unscientific, but we have pretty good evidence that the neural structures that are responsible for a variety of emotions and types of behaviors are conserved in some form across species (in mammals at least.)   Thus, we can be somewhat comfortable in our understanding of the role of play in a rat's cognitive life because, at a pretty complex level of structure and function, they have essentially the same machinery in their head that we do.  It's a bit less convincing to use the same anthropomorphic logic to justify associating what looks like play behavior in an octopus with the "intelligence" that we suspect goes along with play behavior in vertebrates.  This is bec... Read more »

M Kuba, D V Meisel, R A Byrne, U Griebel, & J A Mather. (2003) Looking at Play in Octopus Vulgaris. Coleoid cephalopods through time, 163-169. info:/

  • July 27, 2010
  • 07:00 AM

Bottom trawling and the importance of plaice

by Southern Fried Scientist in Southern Fried Science

“The commons petition the King, complaining that where in creeks and havens of the sea there used to be plenteous fishing, to the profit of the Kingdom, certain fishermen, for several years past have subtily contrived an instrument called the “wondyrechaun” made in the manner of an oyster dredge, but which is considerably longer, upon [...]... Read more »

  • July 27, 2010
  • 07:00 AM

Caloric restriction as a treatment for malignant brain tumors

by EcoPhysioMichelle in C6-H12-O6 (old)

Caloric restriction (CR), which is significantly limiting the intake of food, has been known to increase lifespan and have a reducing effect on non-invasive tumors. CR limits blood glucose levels and forces the body to dip into its fat reserves for energy. These fat deposits are broken down into ketones, which provide an alternate source of fuel for the electron transport chain in the mitochondria. [...]... Read more »

  • July 27, 2010
  • 06:52 AM

The mathematics of marriage, or, less happily ever after

by Becky in It Takes 30

An article I recently ran across in PLoS One (Rey J-M, 2010 A Mathematical Model of Sentimental Dynamics Accounting for Marital Dissolution. PLoS ONE 5: e9881 doi:10.1371/journal.pone.0009881) sets out to provide a mathematical framework for understanding why many marriages fail.  I’d say that qualifies as a topic of general interest, though many might doubt the [...]... Read more »

  • July 27, 2010
  • 05:00 AM

Mitigating climate change with protected areas in the Brazilian Amazon

by Rob Goldstein in Conservation Maven

A recent study examines the effect that 595 protected areas in the Brazilian Amazon have exerted on local deforestation rates. By projecting the effect of these protected areas into the future, the study finds a big impact on carbon emissions...... Read more »

Soares-Filho, B., Moutinho, P., Nepstad, D., Anderson, A., Rodrigues, H., Garcia, R., Dietzsch, L., Merry, F., Bowman, M., Hissa, L.... (2010) Role of Brazilian Amazon protected areas in climate change mitigation. Proceedings of the National Academy of Sciences, 107(24), 10821-10826. DOI: 10.1073/pnas.0913048107  

  • July 26, 2010
  • 09:48 PM

RNA Journal Club 7/15/10

by YPAA in You'd Prefer An Argonaute

Secreted Monocytic miR-150 Enhances Targeted Endothelial Cell Migration Yujing Zhang, Danqing Liu, Xi Chen, Jing Li, Limin Li, Zhen Bian, Fei Sun, Jiuwei Lu, Yuan Yin, Xing Cai, Qi Sun, Kehui Wang, Yi Ba, Qiang Wang, Dongjin Wang, Junwei Yang, Pingsheng Liu, Tao Xu, Qiao Yan, Junfeng Zhang, Ke Zen, and Chen-Yu Zhang Molecular Cell [...]... Read more »

Zhang Y, Liu D, Chen X, Li J, Li L, Bian Z, Sun F, Lu J, Yin Y, Cai X.... (2010) Secreted monocytic miR-150 enhances targeted endothelial cell migration. Molecular cell, 39(1), 133-44. PMID: 20603081  

  • July 26, 2010
  • 01:00 PM

A Giant Among Giants

by Merry Youle in Small Things Considered

Without a doubt, Mimivirus is remarkable. For a virus, it is extraordinarily large and complex. But it is hardly one of a kind. The more that researchers look for large viruses, the more they find.

Although phages generally tend to have small genomes, some managing with but a handful of genes, a glance at the current NCBI list reveals that there are now eight with sequenced genomes that amount to more than 200 kb. A Pseudomonas phage tops the list with 317 kb, but the not-yet-sequenced genome of Bacteriophage G of Bacillus megaterium is reported to be ~670 kb.... Read more »

Van Etten JL. (2003) Unusual life style of giant chlorella viruses. Annual review of genetics, 153-95. PMID: 14616059  

Claverie JM, Ogata H, Audic S, Abergel C, Suhre K, & Fournier PE. (2006) Mimivirus and the emerging concept of "giant" virus. Virus research, 117(1), 133-44. PMID: 16469402  

  • July 26, 2010
  • 12:42 PM

The familiar Matamata, known to us all since the 1700s, and its long, fat neck (matamatas part II)

by Darren Naish in Tetrapod Zoology

Some weeks ago I wrote a bit about the Matamata Chelus fimbriatus: a weird, flat-headed South American pleurodiran turtle. It's one of the strangest creatures tetrapods on the planet, and there's so much to say about it that the previous article ended up being nothing more than the briefest of introductions. Today we start looking at the Matamata in a bit more depth. We start with its affinities and its long neck... Read the rest of this post... | Read the comments on this post...... Read more »

  • July 26, 2010
  • 11:42 AM

Diseases of the Silk Road

by Razib Khan in Gene Expression

Nature has two papers out about something called “Behçet’s disease.” It has apparently also been termed the “Silk Road Disease”, because of its associations with populations connected to the Central Eurasian trade networks.Though described by Hippocrates 2,500 years ago, apparently it was “discovered” only in the 20th century by a Turkish physician. The reason that [...]... Read more »

  • July 26, 2010
  • 10:24 AM

Evolution: You Are What You Eat (and Where You Live)

by Rob Mitchum in ScienceLife

Many people consider human evolution to be a done deal, something that happened in our distant, wild past. But as Nicholas Wade wrote last week in the New York Times, there is increasing scientific evidence that natural selection has continued to act upon humans, producing observable evolutionary changes as recently as 3,000 years ago. Studies [...]... Read more »

Hancock, A., Witonsky, D., Ehler, E., Alkorta-Aranburu, G., Beall, C., Gebremedhin, A., Sukernik, R., Utermann, G., Pritchard, J., Coop, G.... (2010) Colloquium Paper: Human adaptations to diet, subsistence, and ecoregion are due to subtle shifts in allele frequency. Proceedings of the National Academy of Sciences, 107(Supplement_2), 8924-8930. DOI: 10.1073/pnas.0914625107  

  • July 26, 2010
  • 10:10 AM

Dolphin-safe tuna: conservation success story or ecological disaster?

by WhySharksMatter in Southern Fried Science

I used to feel warm and fuzzy inside when I saw the dolphin-safe logo on my tuna. I felt like a decision I made was helping the environment- like I was making a difference.

The commonly believed narrative about dolphin-safe tuna goes something like this: Lots of dolphins were being killed by tuna fishermen, outraged [...]... Read more »

  • July 26, 2010
  • 10:00 AM

Y Chromosome IV: Recombination Suppression

by Kele in Kele's Science Blog

Last time we discussed the discovery of “evolutionary strata” on the human X chromosome – there are distinct blocks on the X that stopped recombining with their Y-homologs at different times causing the Y chromosome’s genes to appear scrambled in order. How can this happen? Note: I apologize for the lack of pictures. None of [...]... Read more »

Joseph E. Ironside. (2010) No amicable divorce? Challenging the notion that sexual antagonism drives sex chromosome evolution. Bioessays, 718-726. info:/10.1002/bies.200900124

  • July 26, 2010
  • 08:37 AM

For Great Apes, Addressing Inequality is Child’s Play

by Eric Michael Johnson in The Primate Diaries in Exile

The #PDEx tour continues hosted by David Dobbs at Neuron Culture.Writing in the Royal Society journal Biology Letters, researchers Edwin Van Leeuwen, Elke Zimmermann, and Marina Davila Ross have shown that gorillas demonstrate an understanding of inequality that they use to modify their behavior under changing social conditions. In more than 85% of the play bouts it was the tagger who made the first move to run as well as the one who ran away. This suggests that there was an implicit understanding that the act of tagging resulted in an unequal relationship and that a response from the individual tagged would therefore be expected. In this way, play teaches important social lessons about inequality and how to respond in a social group.Read the rest of the post here and stay tuned for next Monday's installment at Cocktail Party Physics.Van Leeuwen, E., Zimmermann, E., & Ross, M. (2010). Responding to inequities: gorillas try to maintain their competitive advantage during play fights Biology Letters DOI: 10.1098/rsbl.2010.0482... Read more »

  • July 26, 2010
  • 08:00 AM

Stress endocrine pathway may have preceded vertebrate evolution.

by EcoPhysioMichelle in C6-H12-O6 (old)

Steroid endocrines are all derivatives of cholesterol, and are responsible for metabolism, homeostasis, growth, and reproduction. Some steroid endocrines include the sex endocrines that are responsible for reproduction and the development of secondary sex characteristics, and aldosterone which is important in ion homeostasis. Corticosteroids are also steroid hormones. I’ve blogged about the importance of corticosteroids [...]... Read more »

Close, D., Yun, S., McCormick, S., Wildbill, A., & Li, W. (2010) 11-Deoxycortisol is a corticosteroid hormone in the lamprey. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0914026107  

  • July 26, 2010
  • 07:59 AM

The growing importance of KRAS in ovarian cancer and its impact on pipelines

by Sally Church in Pharma Strategy Blog

We've heard a lot about the impact of KRAS in colorectal cancer as a useful biomarker for determining whether or not to treat with EGFR therapy, depending on whether the mutation is wild-type or mutated, but now new evidence has...... Read more »

Ratner, E., Lu, L., Boeke, M., Barnett, R., Nallur, S., Chin, L., Pelletier, C., Blitzblau, R., Tassi, R., Paranjape, T.... (2010) A KRAS-Variant in Ovarian Cancer Acts as a Genetic Marker of Cancer Risk. Cancer Research. DOI: 10.1158/0008-5472.CAN-10-0689  

Quaye, L., Song, H., Ramus, S., Gentry-Maharaj, A., Høgdall, E., DiCioccio, R., McGuire, V., Wu, A., Van Den Berg, D., Pike, M.... (2009) Tagging single-nucleotide polymorphisms in candidate oncogenes and susceptibility to ovarian cancer. British Journal of Cancer, 100(6), 993-1001. DOI: 10.1038/sj.bjc.6604947  

  • July 26, 2010
  • 07:30 AM

Sustainable RNA Transfection

by avi_wener in American Biotechnologist

MIT scientists Matthew Angel and Mehmet Fatih Yanik have discovered a method for transfecting mRNA into fibroblasts without triggering the immune response that normally defends cells against exogenous RNA infection. Cells are usually able to differentiate between endogenous and exogenous RNA through activation of pattern-recognition receptors (PRRs) that initiate a subsequent immune response. While this [...]... Read more »

Angel M, & Yanik MF. (2010) Innate Immune Suppression Enables Frequent Transfection with RNA Encoding Reprogramming Proteins. PLoS ONE, 5(7). info:/

  • July 26, 2010
  • 06:51 AM

A tale of two circuits

by Becky in It Takes 30

This is a story about a fortunate coincidence.  In two papers published simultaneously last year, the Kirschner lab and the Alon lab each noticed that the signaling pathway they were studying appeared to have peculiar responses.  In both cases, the amount of output — or at least, what had previously been assumed to be the [...]... Read more »

  • July 26, 2010
  • 06:15 AM

Quasispecies thoughts

by iayork in Mystery Rays from Outer Space

Quasispecies theory predicts that slower replicators will be favored if they give rise to progeny that are on average more fit; these populations occupy short, flat regions of the fitness landscape … Flat quasispecies accept mutation without a corresponding effect on fitness … A flat quasispecies with an expansive mutant repertoire can explore vast regions of [...]... Read more »

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