Allison Campbell who alerted me to the integrated state schools that choose not to teach evolution through her posts here and here has taken a similar direction as I have in my post Blow by blow: part 1(see also here). Allison has lightened my load somewhat by commenting on section nine of the Ponatahi Christian School's statement on creation/evolution "[w]hat about archeopteryx?" Many creationists see archeopteryx as some sort of silver bullet (among many others) to evolutionary theory. Allison does a nice job of showing how this the wrong stand to take.
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| Pūkeko (Porphyrio porphyrio melanotus) from wikipedia |
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| A takahē (Porphyrio hochstetteri)from here |
Given their close relation to each other, the pūkeko and takahē are similar in appearance. Both species are bluish in colour with bright red legs and bills. However, the takahē is stockier and has a heavier bill. Furthermore, the takahē is flightless whereas the pūkeko is volant (i.e. it flies), albeit reluctantly, which is typical among rails. As with many New Zealand birds, and island birds in general, flightlessness is common and evolves in the absence of mammalian predators or competitors.
For some more pictures of pūkeko and other NZ native birds check out Chthoniid's Wildlife Photography and for some takahē videos check out the Deparment of Conservation. Also look out for a follow-up post on takahē that will be a little bit sciencier (that is a real word) demonstrating how modern genetic techniques have helped us learn so much more about species distributions. There is a hint about it in the species name for takahē.
G.K. Chesterton: "The Bible tells us to love our neighbours, and also to love our enemies; probably because they are generally the same people."
Harsh but sometimes true.
Noticing a trend in black and white images of the daily quoters. Did all the good things that people can say get used up before the invention of colour photography?
Harsh but sometimes true.
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| From here |
Is this the return of the failed ‘Bird of the week’ posts? Who knows? I won’t commit to a weekly bird post given that the last ‘Bird of the week’ was over nine months ago. I will, however, endeavor to post more about birds at more regular intervals.
Taxonomy | |
Kingdom | Animalia |
Phylum | Chordata |
Class | Aves |
Order | Cuculiformes |
Family | Cuculidae |
Genus | Chrysococcyx |
Species | lucidas |
Today’s bird is quite a charismatic bird in terms of its interesting life history/survival strategy. These birds are brood parasites which means that they lay their eggs in the nests of other birds. The bird is obviously the cuckoo, more specifically the New Zealand Shining Cuckoo or pipiwharauroa (Chrysococcyx lucidus). Shining Cuckoos are so called due to their burnished metallic bronze-green plumage. Easily identified by their aforementioned plumage as well as their distinctive high-pitched call, Shining Cuckoos are a relatively common species found inhabiting native forest, scrub, parks and gardens though out New Zealand. During winter they migrate to Solomon Islands and Bismark Archipelago.
Although brood parasitism is found among other birds, among fish and insects, cuckoos are certainly the most famous of the brood parasites. This is most likely because cuckoos are typically interspecific brood parasites (i.e. they use other species as host parents). The Shining Cuckoo’s usual host is the Grey Warbler. Brood parasitism is more common in Old World cuckoos (~56 species) than in Old World cuckoos (~3 species). All of the former are members of the same family as the Shining Cuckoo, Cuculide, and all are obligate brood parasites. This means that they are ‘obliged’ to put their eggs in someone else's basket. However, whose basket is the question.
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| Photo credit: Peter Woods taken from http://www.nzbirds.com |
One of the common strategies for cuckoos to get a host to sit on their eggs is to mimic the appearance of the host’s eggs. As mentioned previously, the Shining Cuckoo uses the Grey Warbler as a host. Therefore, under an evolutionary arms race scenario, the cuckoo would be under selection to produce better and better mimetic eggs and the host would attempt to counter this with some sort of anti-parasitism defence (note: do not interpret the scenario as teleological). We should therefore expect that a single species of cuckoo would have a singly host species. Interestingly, this is not always the case. Some species of cuckoos have several host species and the way they get this right is by having polymorphic eggs. This means that within a species of cuckoo, different individuals lay eggs that look different and mimic the eggs of a different host species. But how does this happen and why do some individuals have different eggs?
The first question you would need to ask is how the females know which species has eggs that look like their own, and the second one would be why do females lay the same eggs as their mother if they mate with a male born to a female of a different egg type. The first question is relatively straight forward. The female is likely to carry some sort of imprint from the song and appearance of her surrogate mother making it easier for her to identify a host when she needs to lay her eggs. This is particularly important in areas where the different host species have overlapping geographic ranges. The second question has a remarkable potential answer. In mammals, males carry one X and one Y chromosome and females carry two X chromosomes. In birds, however, females carry one W and one Z chromosome and males carry two Z chromosomes. It is therefore possible that the gene related to egg colour determination in cuckoos is carried in the W chromosome. Therefore, it doesn’t matter what egg type male was born from, it is only the female that matters.
Mimetic eggs are not the only way that cuckoos get away with brood parasitism. In some species the egg does not resemble the hosts’ eggs. How then does the cuckoo get away with it? Historically it has been suggested there might be lag in the evolution of the host such that there has not been enough time to evolve defenses or, the host is genetically constrained somehow and unable to evolve a defense. This means that the evolutionary arms race is in disequilibrium. A recent study of the Jacobin Cuckoo (Clamator jacobinus) and its host the Cape bulbul (Pycnonotus capensis) suggests that in this case it might actually be stable. This is an example of a non-mimetic egg host–parasite relationship because eggs of the Jacobin Cuckoo are almost twice the size of the eggs of the Cape Bulbul. Given this non-mimetic nature of the cuckoo eggs it would be easy for the Bulbul to recognise the imposter but the eggs are probably too heavy to eject from the nest and too thick to break open. Why does the Bulbul not just desert the nest in the presence of a cuckoo egg? Despite cuckoo eggs and/or chicks being present in the nest the author found that the fitness of the Bulbul was not reduced to zero. In other words some Bulbul offspring did survive to fledge in the presence of cuckoo chicks. Thus, if the Bulbul does abandon the nest its own chicks would die, effectively reducing its own fitness. This work is interesting because evolutionary lag has tended to be the typical explanation for the non-mimetic phenomenon among cuckoos. It also indicates the importance of questioning ideas carefully in science and not sticking to the status quo.
I am literally (Paul) not going to introduce today's quoter. I propose guessing who it is without the use of google and posting your guess in the comments.
"We must, however, acknowledge, as it seems to me, that man with all his noble qualities . . . still bears in his bodily frame the indelible stamp of his lowly origin"
"We must, however, acknowledge, as it seems to me, that man with all his noble qualities . . . still bears in his bodily frame the indelible stamp of his lowly origin"
Over the last decade blogging and other social media has become a part of most of our lives. This surge has been seen in the science community too. Platforms like freethoughtblogs, home to PZ Myers' blog Pharyngula, New Zealand's own sciblogs exemplify this growth. It has got to a point where you need to have an online presence to be noticed. I have taken this route too. I have a blog (obviously) and I have a twitter account as of this week.
Social media has been a hugely positive for science. Disseminating of ideas and new discoveries can be notoriously slow in the scientific literature, particularly in high impact journals that receive literally hundreds of submissions from hopeful scientists every day. Social media and blogging on the other hand allows rapid sharing of ideas, and in recent times it has been the vehicle of criticism. There are two notable examples that come to mind although I am sure there are many others: (1) the famous 'arsenic-life' paper, and (2) the 'velvet worm--insect hybrid' paper.
The first example, 'arsenic life', exploded in the scientific blogging community. A Google search of arsenic life yields 11,300,000 hits. The original work was published in one of the most prominent journals, Science, but was preceded by a press release by NASA who funded the research. The press release was tantalizing and alluded to the discovery of extraterrestrial life. This was not the case. What the research apparently showed was that bacteria, named GFAJ-1, was not only growing in high levels or arsenic, but actually incorporating arsenate into it's DNA 'backbone'. This is significant because all life on Earth as we knew it until then used phosphate in it's DNA backbone--GFAJ-1 was essentially replacing phosphate with arsenate.
Unsurprisingly, such a bold claim is always approached with skepticism in the science community. However, this work was met with more than just skepticism. It was met with disbelief and harsh criticism. I have taken the time to Google that for you, all you need to do is click here to see the results. In fact about six months later Science published no less than eight technical comments on the original arsenic life paper along with a reply from the original authors. However, it was blogging that started it all. Probably the most outspoken and prominent critics was Rosie Redfield. Rosie is now trying to reproduce the results of the arsenic life paper with a live diary of her progress. To date she has been unable to replicate the growth reported by Wolfe-Simon et al. (arsenic life). We are left with several different conclusions we can draw thus far. One of them is clearly that Wolfe-Simon et al are did something dodgy. Another is that Rosie Redfield is doing something different that is inhibiting the growth of GFAJ-1 in her arsenate medium. Because Rosie is live blogging her progress and getting advice from readers the second seems unlikely, but who knows. None the less, it is an excellent example of a scientist using social media to improve science in general.
The second example is a paper by Donald I. Williamson published in another high impact journal, the Proceedings of the National Academy of Science. The paper proposed a bold new idea that Williamson claimed would change the way we should view evolution. He claimed that holometabolous species (e.g. butterflies) are not decedents of a single lineage, but rather the result of an ancient hybridization between two lineages; one that resembles the larval form and one that resembles the adult form.
The example that Williamson put forward in his 2009 paper was Lepidoptera.Williamson claimed that the two distinct forms that butterflies and moths take in their life cycle (i.e. caterpillar and flying adult) resulted from the 'unholy matrimony' between a velvet worm and an butterfly or moth-like insect. To the casual observer this might sound crazy, but at the same time wonderfully appealing. In fact, looking at a caterpillar it might be easy to believe that they are more closely related to velvet worms than butterflies. See the picture below. However, there are several lines of argument along with empirical evidence that demonstrates that caterpillars and butterflies are indeed one lineage separate from velvet worms. This evidence was presented by several authors in follow-up commentary published in PNAS that severely criticised Williamson's work. See here and here.
The formal criticisms published in PNAS are an example of science in working and PNAS should be applauded for this. However, the biggest question that should be asked is, how was this work published in the first place given the significant flaws? This was discussed and debated heavily online and it was the online science community that really got people interested in making formal comments. My favourite quote from an online source is from Fred Nijhout saying that the paper would be better suited to "National Enquirer than [PNAS]."
Social media has been a hugely positive for science. Disseminating of ideas and new discoveries can be notoriously slow in the scientific literature, particularly in high impact journals that receive literally hundreds of submissions from hopeful scientists every day. Social media and blogging on the other hand allows rapid sharing of ideas, and in recent times it has been the vehicle of criticism. There are two notable examples that come to mind although I am sure there are many others: (1) the famous 'arsenic-life' paper, and (2) the 'velvet worm--insect hybrid' paper.
The first example, 'arsenic life', exploded in the scientific blogging community. A Google search of arsenic life yields 11,300,000 hits. The original work was published in one of the most prominent journals, Science, but was preceded by a press release by NASA who funded the research. The press release was tantalizing and alluded to the discovery of extraterrestrial life. This was not the case. What the research apparently showed was that bacteria, named GFAJ-1, was not only growing in high levels or arsenic, but actually incorporating arsenate into it's DNA 'backbone'. This is significant because all life on Earth as we knew it until then used phosphate in it's DNA backbone--GFAJ-1 was essentially replacing phosphate with arsenate.
Unsurprisingly, such a bold claim is always approached with skepticism in the science community. However, this work was met with more than just skepticism. It was met with disbelief and harsh criticism. I have taken the time to Google that for you, all you need to do is click here to see the results. In fact about six months later Science published no less than eight technical comments on the original arsenic life paper along with a reply from the original authors. However, it was blogging that started it all. Probably the most outspoken and prominent critics was Rosie Redfield. Rosie is now trying to reproduce the results of the arsenic life paper with a live diary of her progress. To date she has been unable to replicate the growth reported by Wolfe-Simon et al. (arsenic life). We are left with several different conclusions we can draw thus far. One of them is clearly that Wolfe-Simon et al are did something dodgy. Another is that Rosie Redfield is doing something different that is inhibiting the growth of GFAJ-1 in her arsenate medium. Because Rosie is live blogging her progress and getting advice from readers the second seems unlikely, but who knows. None the less, it is an excellent example of a scientist using social media to improve science in general.
The second example is a paper by Donald I. Williamson published in another high impact journal, the Proceedings of the National Academy of Science. The paper proposed a bold new idea that Williamson claimed would change the way we should view evolution. He claimed that holometabolous species (e.g. butterflies) are not decedents of a single lineage, but rather the result of an ancient hybridization between two lineages; one that resembles the larval form and one that resembles the adult form.
The example that Williamson put forward in his 2009 paper was Lepidoptera.Williamson claimed that the two distinct forms that butterflies and moths take in their life cycle (i.e. caterpillar and flying adult) resulted from the 'unholy matrimony' between a velvet worm and an butterfly or moth-like insect. To the casual observer this might sound crazy, but at the same time wonderfully appealing. In fact, looking at a caterpillar it might be easy to believe that they are more closely related to velvet worms than butterflies. See the picture below. However, there are several lines of argument along with empirical evidence that demonstrates that caterpillars and butterflies are indeed one lineage separate from velvet worms. This evidence was presented by several authors in follow-up commentary published in PNAS that severely criticised Williamson's work. See here and here.
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| Caterpillar of Theretra oldenlandiae I think. Taken from here |
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| Velvet worm from New Zealand (peripatus). Photo by S. Moore |
Sir William Schwenck Gilbert: "[a]nd isn't you life extremely flat whit nothing whatever to grumble at!"
Well said Sir Gilbert. A life without grumbling would be boring indeed. W.S. Gilbert is the Gilbert of Gilbert and Sullivan who produced the musicals The Pirates of Penzance and The Mikado.
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| Sir W.S. Gilbert: image from Encyclopedia Britannica |
Well said Sir Gilbert. A life without grumbling would be boring indeed. W.S. Gilbert is the Gilbert of Gilbert and Sullivan who produced the musicals The Pirates of Penzance and The Mikado.
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