Explain the butterfly

[Dreadnought]

For several years this was the battlecry of one grandmaster of chess who had taken a dislike to the theory of evolution (actually he exclusively used the term neo-Darwinism for some reason I could never quite fathom). This was and is a fairly intelligent fellow and not a creationist as such, in fact he didn't have an alternative to evolution at all, but he was still strongly opposed to it. I tried to invite him here, but regrettably he turned it down. Anyway, none of the people frequenting that chat channel at the time had anything near the expertise that is present here and we were never able to produce an explanation that was acceptable to the gentleman in question and for all I know we were all wrong anyway.

So the question is: How did the butterfly (or any other metamorphosing species) evolve to have a long larvae stage followed by a metamorphosis into a seemingly completely different bugger?

[Monad]

I wouldn't claim to be an expert but my own view is holometabolism ("complete" metamorphosis in insects as opposed to partial) is a strategy that enables them to get round some of the limitations of the arthropod body plan. Having a rigid exoskeleton means in order to grow an insect has to periodically shed it's skin. This means that during the juvenile phase of development where growth has to be most rapid in the progression towards adulthood, there are going to have to be lots of moultings and therefore also lots of periods of vulnerability. Many hemimetabolous insects get around this to an extent by adopting strategies such as the immature stage being hidden underground or underwater for long periods (as in cicadas and mayflies) and then timing their emergence so they all emerge at once and overwhelm predators through sheer force of numbers. Holometabolous insects seem to have adopted a different strategy that obviously works quite well (as they are so successful). What they do is have a larval stage that is essentially just a simplified expandable bag with legs - a dedicated eating machine that still needs to moult but has the capability to grow more rapidly between moults as it doesn't have as rigid a skin. By having a clear cut division of labour between stages they can make each stage more dedicated to and specialised for their role - one stage for eating and growing, one for hiding and changing (the pupa) and one for mating and disseminating the next generation.

[Jet Black]

well there are all sorts of levels of metamorphosis in arthropods from not-at-all to complete metamorphosis. The various staps are pretty much there in nature.

[Ray Moscow]

ID and creationist arguments usually come back to one's ignorance, incredulity, or both.

If the creationist is interested in looking at evidence, you can point him/her to a few examples of transitional forms, then a few more, etc.

I remember reading a review of a recent volume on the evolution of insects, but as I haven't read the book itself I won't mention which one.

[Martin B]

Most peoples' problems along these lines usually boil down to an ignorance of biological diversity. As others have pointed out, there is a wide range of life history strategies in insects. What I would do is question why this guy singled out butterflies. As him why it is so important that he asks about butterflies. Are they special in regards to other insects? Or other animals? Ask him what he knows about the metamorphosis of other insects. The main thing is to ask him lots of questions about his own position, as this will make it easier to expose the fact that his problem is most likely borne out of ignorance, and not out of sound reasoning.

[Jet Black]

Most peoples' problems along these lines usually boil down to an ignorance of biological diversity. As others have pointed out, there is a wide range of life history strategies in insects. What I would do is question why this guy singled out butterflies. As him why it is so important that he asks about butterflies. Are they special in regards to other insects? Or other animals? Ask him what he knows about the metamorphosis of other insects. The main thing is to ask him lots of questions about his own position, as this will make it easier to expose the fact that his problem is most likely borne out of ignorance, and not out of sound reasoning.

nice suggestion that.

[Calilasseia]

What I would do is question why this guy singled out butterflies. As him why it is so important that he asks about butterflies.

Might have something to do with the fact that butterflies are pretty to look at and thus don't evoke the same awkward questions about how an infinitely benevolent god can be responsible for utterly nasty creatures that would result the moment one lined up Tsetse flies, Fire Ants or Cochliomyia hominivorax for people to look at. :)

Mind you, I learned today, whilst trawling for information on Diptera, that there is such a creature as the Fire Ant Decapitating Fly. Pseudacteon curvatus is a parasitic fly that can be found from Brazil to Argentina, and which is a parasite of Fire ants, in particular members of the Solenopsis saevissima species complex. Apparently, the life cycle is as follows. The female fly alights upon a worker Fire Ant, moving quickly to one side, before injecting a single egg into the ant's thorax using a needle-like penetrating ovipositor that drives through the ant's exoskeleton. The egg hatches, and the fly larva migrates to the head of the worker ant it is now occupying. During this time, the worker ant appears to behave normally. After three instars of development, the larva then turns its attention to eating the contents of the ant's head from the inside out. Needless to say, this kills the ant. It also causes the ant's head to drop off its body, hence the name "Fire Ant Decapitating Fly". The fly larva then pupates inside the vacated ant head capsule, and upon transforming to an adult fly, then emerges from the oral cavity of the deceased ant's head. The size of worker ant that receives the egg in the first place apparently determines the sex of the adult fly - small worker ants, when parasitised, give rise to female flies, whilst large worker ants give rise to male flies.

Needless to say, these flies are being studied as a means of controlling introduced Solenopsis Fire Ant infestations in the USA, because whilst the flies only kill a small number of ants, they have a disproportionately large effect upon the behaviour of the ant colony. Once an ant colony becomes aware that these flies are present, they forage over considerably shorter distances to minimise the risk of parasite attack, and consequently their resource acquisition is reduced by 50%, which in turn limits the size of the ant colony.

[David B]

I'm wondering if there is anything to suggest whether this is an evolutionary strategy that has been 'invented' more than once, or whether all creatures with this strategy have a common ancestor.

David B

[Obd]

I'm wondering if there is anything to suggest whether this is an evolutionary strategy that has been 'invented' more than once, or whether all creatures with this strategy have a common ancestor.

David B

Well they do have a common ancestor, but that doesn't mean it can't have been 'invented' more than once.

[SteveF]

Not directly related to the question in the OP, but quite a lot of interesting work has been done on butterfly evolution, particularly of the wing. A lot of this has had an evo-devo flavour. There is this now classic paper:

Brakefield, P.M. (1996) Development, plasticity and evolution of butterfly eyespot patterns. Nature, 384, 236-242.

The developmental and genetic bases for the formation, plasticity and diversity of eyespot patterns in butterflies are examined. Eyespot pattern mutants, regulatory gene expression, and transplants of the eyespot developmental organizer demonstrate that eyespot position, number, size and colour are determined progressively in a developmental pathway largely uncoupled from those regulating other wing-pattern elements and body structures. Species comparisons and selection experiments suggest that the evolution of eyespot patterns can occur rapidly through modulation of different stages of this pathway, and requires only single, of very few, changes in regulatory genes.

Most recently, we have this excellent paper, which contains a nice review:

Saenko, S.V. et al. (2008) Conserved developmental processes and the formation of evolutionary novelties: examples from butterfly wings. Philosophical Transactions of the Royal Society B - Biological Sciences, 363, 1549-1555.

The origin and diversification of evolutionary novelties - lineage-specific traits of new adaptive value - is one of the key issues in evolutionary developmental biology. However, comparative analysis of the genetic and developmental bases of such traits can be difficult when they have no obvious homologue in model organisms. The finding that the evolution of morphological novelties often involves the recruitment of pre-existing genes and/or gene networks offers the potential to overcome this challenge. Knowledge about shared developmental processes obtained from extensive studies in model organisms can then be used to understand the origin and diversification of lineage-specific structures. Here, we illustrate this approach in relation to eyespots on the wings of Bicyclus anynana butterflies. A number of spontaneous mutations isolated in the laboratory affect eyespots, lepidopteran-specific features, and also processes that are shared by most insects. We discuss how eyespot mutants with disturbed embryonic development may help elucidate the genetic pathways involved in eyespot formation, and how venation mutants with altered eyespot patterns might shed light on mechanisms of eyespot development.

They conclude:

We reported on the analysis of a number of spontaneous mutants in B. anynana butterflies which affect eyespot patterning (a lepidopteran novelty) and other developmental processes that are conserved across insects (namely, embryogenesis or wing vein development). Analysis of these mutants in the context of the extensive genetic and developmental knowledge available for model systems holds promise for furthering our understanding of the origin and diversification of butterfly eyespots.

(a) Shared developmental processes and evolutionary novelties

Among the different genetic mechanisms that have been proposed to account for the origin of novel traits, it is the redeployment of existing pathways that is discussed here. The fact that some shared pathways are reutilized to produce novel structures (with more or less modification of the components therein) offers the potential for using the extensive knowledge of such pathways coming from model organisms, to understand structures present in other systems. Here, we have illustrated this approach using laboratory mutations in B. anynana with pleiotropic effects on eyespot patterns and either embryonic development or wing venation, both well studied in D. melanogaster. This approach can, in theory, be used to analyse a whole suite of novel traits in any insect species provided pleiotropic mutants have been identified and can be kept in the laboratory.

Wound healing is another example of a fundamental process that is likely to be shared by all animals and might have been co-opted in the evolution of eyespots. Damage of wing tissue in early pupae can lead to the formation of ectopic eyespots (Brakefield & French 1995), probably via the upregulation of expression of characteristic 'eyespot genes' (e.g. Distal-less, engrailed and spalt) in scale-building cells around the wound site (Monteiro et al. 2006). Detailed analysis of such shared genetic networks in the context of eyespot formation will be invaluable for our understanding of the evolutionary diversification of butterfly eyespots.

(b) Mutations of large effect and morphological diversification

A related issue of great importance in evo-devo is that of the genetic and developmental mechanisms underlying phenotypic variation. In particular, the extent to which mutants of large effect identified in the laboratory are relevant for natural variation within and across species is a matter of debate (see Haag & True 2001). While it seems unlikely that recessive lethal alleles such as Goldeneye will contribute to eyespot variation in natural populations (unless there is a strong heterozygote advantage), it is possible that the same loci harbour other alleles, relevant for variation in eyespot patterns. Also, while mutations that eliminate wing veins and lead to rapid wing damage and, consequently, to reduction in flight ability (as in Cyclops and veinless) are unlikely to be favoured by natural selection, more localized changes in venation or vein additions (as in extra veins) might be relevant mechanisms for wing pattern evolution. Future work will explore the extent to which loci identified in laboratory eyespot mutants contribute to quantitative variation segregating in natural populations and potentially fixed across species.

We have illustrated how studies of B. anynana wing patterns and, in particular, of eyespot mutants, can shed light on some of the most exciting questions in evo-devo. Butterfly eyespots, like some other evolutionary novelties, have evolved largely via the redeployment of genetic circuitry involved in other, shared, developmental processes. The study of the latter and the comparison with model insects offer a new approach to studying the origin and diversification of lineage-specific structures.

[SteveF]

Just thought I'd update this with a couple of interesting butterfly related evolution papers:

Allen, C.E. et al. (2008) Differences in the selection response of serially repeated color pattern characters: Standing variation, development, and evolution. BMC Evolutionary Biology, 8, doi:10.1186/1471-2148-8-94.

Background

There is spectacular morphological diversity in nature but lineages typically display a limited range of phenotypes. Because developmental processes generate the phenotypic variation that fuels natural selection, they are a likely source of evolutionary biases, facilitating some changes and limiting others. Although shifts in developmental regulation are associated with morphological differences between taxa, it is unclear how underlying mechanisms affect the rate and direction of evolutionary change within populations under selection.

Here we focus on two ecologically relevant features of butterfly wing color patterns, eyespot size and color composition, which are similarly and strongly correlated across the serially repeated eyespots. Though these two characters show similar patterns of standing variation and covariation within a population, they differ in key features of their underlying development. We targeted pairs of eyespots with artificial selection for coordinated (concerted selection) versus independent (antagonistic selection) change in their color composition and size and compared evolutionary responses of the two color pattern characters.

Results

The two characters respond to selection in strikingly different ways despite initially similar patterns of variation in all directions present in the starting population. Size (determined by local properties of a diffusing inductive signal) evolves flexibly in all selected directions. However, color composition (determined by a tissue-level response to the signal concentration gradient) evolves only in the direction of coordinated change. There was no independent evolutionary change in the color composition of two eyespots in response to antagonistic selection. Moreover, these differences in the directions of short-term evolutionary change in eyespot size and color composition within a single species are consistent with the observed wing pattern diversity in the genus.

Conclusion

Both characters respond rapidly to selection for coordinated change, but there are striking differences in their response to selection for antagonistic, independent change across eyespots. While many additional factors may contribute to both short- and long-term evolutionary response, we argue that the compartmentalization of developmental processes can influence the diversification of serial repeats such as butterfly eyespots, even under strong selection.

http://www.biomedcentral.com/1471-2148/8/94

and

Neve, G. et al. (2008) Gene flow rise with habitat fragmentation in the bog fritillary butterfly (Lepidoptera: Nymphalidae). BMC Evolutionary Biology, 8, doi:10.1186/1471-2148-8-84.

Background

The main components of the spatial genetic structure of the populations are neighbourhood size and isolation by distance. These may be inferred from the allele frequencies across a series of populations within a region. Here, the spatial population structure of Proclossiana eunomia was investigated in two mountainous areas of southern Europe (Asturias, Spain and Pyrenees, France) and in two areas of intermediate elevation (Morvan, France and Ardennes, Belgium).

Results

A total of eight polymorphic loci were scored by allozyme electrophoresis, revealing a higher polymorphism in the populations of southern Europe than in those of central Europe.

Isolation by distance effect was much stronger in the two mountain ranges (Pyrenees and Asturias) than in the two areas of lower elevation (Ardennes and Morvan). By contrast, the neighbourhood size estimates were smaller in the Ardennes and in the Morvan than in the two high mountain areas, indicating more common movements between neighbouring patches in the mountains than in plains.

Conclusion

Short and long dispersal events are two phenomena with distinct consequences in the population genetics of natural populations. The differences in level of population differentiation within each the four regions may be explained by change in dispersal in lowland recently fragmented landscapes: on average, butterflies disperse to a shorter distance but the few ones which disperse long distance do so more efficiently. Habitat fragmentation has evolutionary consequences exceeding by far the selection of dispersal related traits: the balance between local specialisation and gene flow would be perturbed, which would modify the extent to which populations are adapted to heterogeneous environments.

http://www.biomedcentral.com/1471-2148/8/84

[Matty]

Mind you, I learned today, whilst trawling for information on Diptera, that there is such a creature as the Fire Ant Decapitating Fly. Pseudacteon curvatus is a parasitic fly that can be found from Brazil to Argentina, and which is a parasite of Fire ants, in particular members of the Solenopsis saevissima species complex. Apparently, the life cycle is as follows. The female fly alights upon a worker Fire Ant, moving quickly to one side, before injecting a single egg into the ant's thorax using a needle-like penetrating ovipositor that drives through the ant's exoskeleton. The egg hatches, and the fly larva migrates to the head of the worker ant it is now occupying. During this time, the worker ant appears to behave normally. After three instars of development, the larva then turns its attention to eating the contents of the ant's head from the inside out. Needless to say, this kills the ant. It also causes the ant's head to drop off its body, hence the name "Fire Ant Decapitating Fly". The fly larva then pupates inside the vacated ant head capsule, and upon transforming to an adult fly, then emerges from the oral cavity of the deceased ant's head. The size of worker ant that receives the egg in the first place apparently determines the sex of the adult fly - small worker ants, when parasitised, give rise to female flies, whilst large worker ants give rise to male flies. Well thats me done. If that isnt the work of a benevolant and all loving God, i dont know what is.

[Dlx2]

What I would do is question why this guy singled out butterflies.

My guess: he's Russian and he's citing the argument by Vladimir Nabokov.

[VoxRat]

What I would do is question why this guy singled out butterflies.

My guess: he's Russian and he's citing the argument by Vladimir Nabokov.
Was Nabokov an anti-evolutionist?
Oh well. I guess that may go with the territory of being eccentric.

I admire Nabokov's writing over just about anyone's. I think "Ada" is my all-time favorite novel.

And I know he was a maniac for butterflies.

[Dlx2]

What I would do is question why this guy singled out butterflies.

My guess: he's Russian and he's citing the argument by Vladimir Nabokov.
Was Nabokov an anti-evolutionist?
Oh well. I guess that may go with the territory of being eccentric.

I admire Nabokov's writing over just about anyone's. I think "Ada" is my all-time favorite novel.

And I know he was a maniac for butterflies.

He had this concept of God as Author and found certain things, especially butterflies, to be "evidence" of the authorial skill of God. I mean, that was the entire point of Ada as well as Invitation to a Beheading and even Lolita. The idea has aesthetic appeal beyond the "god as enginerd" hypothesis of YECs, but aesthetic appeal has little truth value. All in all, Nabokov was a reflection of where he came from; he was an early 20th century Russian aristocrat ex-pat with the requisite pretension and adhesion to enlightenment-era ideals.

Invitation to a Beheading, though, is one of my favorite books, though, and I do absolutely love Nabokov's work in general. Ada is delicious, but the constant argument with Proust and Borges sometimes really gets on my nerves.

[clivedurdle]

Is not the fire ant decapititating fly only using a different ecological niche for its larvae to develop?

This is just one more for the list

eggs floating in water, fish, frogs etc, hard eggs, birds reptiles, eggs inside mum, mammals, marsupials, hard eggs but milk - platypus, hole dwelling animals using the shelter of the cave or hole.

An ant's head is only another variation, why get fussed about it?

Insects seem to have evolved a whole series of tricks - metamorphosis sounds like it is about changing your own body as a way of changing niches. This fly is just using someone else's body. (Sorry - head).

Instead of looking at what individual species do, why not look at the processes and solutions evolution has "found"?

I may even argue that the terms parasite and metamorphis should be abolished - parasite is perjorative - in favour of life stage solutions living inside something else. or externally or whatever the niche is.

Remember the barnacle studied by Darwin with the stripped down male living on the female and consisting of not much more than a sperm sac. Is he a parasite?

We might ask questions like what possible solutions are missing?

[Dlx2]

I may even argue that the terms parasite and metamorphis should be abolished - parasite is perjorative - in favour of life stage solutions living inside something else. or externally or whatever the niche is.

"Parasite" is neither perjorative nor is it a useless term so long as one is looking at the scale of ecology.

Metamorphosis is a very useful term when discussing drastically different niche occupation by adults and larvae with no gradual transition between the two.

Attacking terminology seems pointless when that terminology is very useful.

[Steviepinhead]

My guess: he's Russian and he's citing the argument by Vladimir Nabokov.
Was Nabokov an anti-evolutionist?
Oh well. I guess that may go with the territory of being eccentric.

I admire Nabokov's writing over just about anyone's. I think "Ada" is my all-time favorite novel.

And I know he was a maniac for butterflies.

He had this concept of God as Author and found certain things, especially butterflies, to be "evidence" of the authorial skill of God. I mean, that was the entire point of Ada as well as Invitation to a Beheading and even Lolita. The idea has aesthetic appeal beyond the "god as enginerd" hypothesis of YECs, but aesthetic appeal has little truth value. All in all, Nabokov was a reflection of where he came from; he was an early 20th century Russian aristocrat ex-pat with the requisite pretension and adhesion to enlightenment-era ideals.

Invitation to a Beheading, though, is one of my favorite books, though, and I do absolutely love Nabokov's work in general. Ada is delicious, but the constant argument with Proust and Borges sometimes really gets on my nerves.
Nabokov also wrote an entire novel about a chess master during his emigre period in Berlin: The Defense, aka The Luzhin Defense, published in 1930. During the same period, Nabokov enjoyed constructing chess problems. Perhaps this strengthens our tentative association between Nabokov and the actual creationist chess master cited in the OP...

[Calilasseia]

Oh, by the way Clive, you'll be interested to know, while mentioning eggs floating in water, that one fish lays its eggs out of water.

Copella arnoldi, the Splashing Tetra, is a small Characin from the Amazon. Males and females are visually sexually dimorphic, with males having much longer and more ornate finnage, and in particular a certain asymmetry to the tail fin not seen in females. The reason for this becomes apparent when you watch them breeding, and these fishes will happily breed in an aquarium if you set it up correctly.

In the wild, the male positions himself under a leaf that is about 2 inches above the water surface. He then entices females to mate with him. The mating embrace then takes place, and both fishes leap out of the water, and for a short time, adhere to the underside of the chosen leaf for a couple of seconds whilst the female lays around 10-12 eggs, and the male fertilises them. This is repeated until the male has amassed between 100 and 200 fertilised eggs upon his chosen leaf.

The male then darts from cover periodically, and using the extended and slightly asymmetrical tail fin, splashes the eggs to keep them moist. The eggs take around 2 days to hatch at 80°F, and when the fry have emerged from the eggshells, they drop into the water and head for cover as fast as they can, the male standing guard for the duration.

In an aquarium, you can provide the fishes with a breeding aquarium by including some fine leaved plants for the young to hide in once free-swimming, leaving a 2 inch gape between the water surface and the cover glass. Place a piece of thin green cardboard on top of the cover glass to mimic the overhanging leaf. The fishes will deposit their spawn under that.

[Jobar]

Mind you, I learned today, whilst trawling for information on Diptera, that there is such a creature as the Fire Ant Decapitating Fly. Pseudacteon curvatus is a parasitic fly that can be found from Brazil to Argentina, and which is a parasite of Fire ants, in particular members of the Solenopsis saevissima species complex. Apparently, the life cycle is as follows. The female fly alights upon a worker Fire Ant, moving quickly to one side, before injecting a single egg into the ant's thorax using a needle-like penetrating ovipositor that drives through the ant's exoskeleton. The egg hatches, and the fly larva migrates to the head of the worker ant it is now occupying. During this time, the worker ant appears to behave normally. After three instars of development, the larva then turns its attention to eating the contents of the ant's head from the inside out. Needless to say, this kills the ant. It also causes the ant's head to drop off its body, hence the name "Fire Ant Decapitating Fly". The fly larva then pupates inside the vacated ant head capsule, and upon transforming to an adult fly, then emerges from the oral cavity of the deceased ant's head. The size of worker ant that receives the egg in the first place apparently determines the sex of the adult fly - small worker ants, when parasitised, give rise to female flies, whilst large worker ants give rise to male flies. Well thats me done. If that isnt the work of a benevolant and all loving God, i dont know what is.

Well, yeah; but the fact that this is happening to fire ants might be used as an argument AGAINST a *totally malevolent* god.

sez Jobar, who was just today trying to destroy some of the abundant fire ant mounds in his yard

[Dlx2]

Oh, by the way Clive, you'll be interested to know, while mentioning eggs floating in water, that one fish lays its eggs out of water.

Copella arnoldi, the Splashing Tetra, is a small Characin from the Amazon. Males and females are visually sexually dimorphic, with males having much longer and more ornate finnage, and in particular a certain asymmetry to the tail fin not seen in females. The reason for this becomes apparent when you watch them breeding, and these fishes will happily breed in an aquarium if you set it up correctly.

In the wild, the male positions himself under a leaf that is about 2 inches above the water surface. He then entices females to mate with him. The mating embrace then takes place, and both fishes leap out of the water, and for a short time, adhere to the underside of the chosen leaf for a couple of seconds whilst the female lays around 10-12 eggs, and the male fertilises them. This is repeated until the male has amassed between 100 and 200 fertilised eggs upon his chosen leaf.

The male then darts from cover periodically, and using the extended and slightly asymmetrical tail fin, splashes the eggs to keep them moist. The eggs take around 2 days to hatch at 80°F, and when the fry have emerged from the eggshells, they drop into the water and head for cover as fast as they can, the male standing guard for the duration.

In an aquarium, you can provide the fishes with a breeding aquarium by including some fine leaved plants for the young to hide in once free-swimming, leaving a 2 inch gape between the water surface and the cover glass. Place a piece of thin green cardboard on top of the cover glass to mimic the overhanging leaf. The fishes will deposit their spawn under that.

Anchovies, capelin, grunion, and a few other species lay their eggs in beachsand, too.