Leaf like bugs

The accumulation of small heritable changes within populations over time.

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Leaf like bugs

#1  Postby Passer » Dec 26, 2010 12:03 pm

Concerning evolution, how does it explain the bug that changes itself to look like a leaf? Does it explain it the same way as other forms of life? I've heard tell of a butterfly or more probably a moth, I can't quite remember now, but it evolved into two different types. One type, because it spends its time mostly in rural areas, is white in colour, but the other type, because it spends most of its time in and around a dirty industrialised area, is more grey in its colouring.

But the bug resembling a leaf seems a bit of a stretch.
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Re: Leaf like bugs

#2  Postby Scar » Dec 26, 2010 12:08 pm

There more a bug blends into it's surrounding the better it evades possible predators (or the better it is at fooling it's prey).

You have to keep in mind that evolution does not suddenly turn a bug into a leaf-like form - it's happening gradually. With every generation, the bugs that are better at blending in will be more successfull.
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Re: Leaf like bugs

#3  Postby NineBerry » Dec 26, 2010 12:17 pm

Watch this video:

http://youtu.be/YT1vXXMsYak

The relevant part starts at 45 minutes in.
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Re: Leaf like bugs

#4  Postby Sityl » Dec 26, 2010 1:27 pm

Passer wrote:Concerning evolution, how does it explain the bug that changes itself to look like a leaf? Does it explain it the same way as other forms of life? I've heard tell of a butterfly or more probably a moth, I can't quite remember now, but it evolved into two different types. One type, because it spends its time mostly in rural areas, is white in colour, but the other type, because it spends most of its time in and around a dirty industrialised area, is more grey in its colouring.

But the bug resembling a leaf seems a bit of a stretch.


This is a good question, Passer, and I don't think anyone could do as good of a job at explaining it than Carl Sagan. Please watch this video, it's short but spot on.

[youtube]http://www.youtube.com/watch?v=dIeYPHCJ1B8[/youtube]
Stephen Colbert wrote:Now, like all great theologies, Bill [O'Reilly]'s can be boiled down to one sentence - 'There must be a god, because I don't know how things work.'


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Re: Leaf like bugs

#5  Postby Paul G » Dec 26, 2010 5:50 pm

Aren't you just asking how does a species evolve to camouflage itself?

Bugs are of course not the only animals that have evolved to look like leaves...

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Re: Leaf like bugs

#6  Postby twistor59 » Dec 26, 2010 6:24 pm

When I read the title I just couldn't help thinking "tits like coconuts"
A soul in tension that's learning to fly
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Can't keep my eyes from the circling skies
Tongue-tied and twisted just an earthbound misfit, I
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Re: Leaf like bugs

#7  Postby Passer » Dec 26, 2010 6:58 pm

twistor59 wrote:When I read the title I just couldn't help thinking "tits like coconuts"

Ok that made me chuckle :grin:

EDIT: Thank you all very much for the info/links, I'll get into them as soon as possible.
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Re: Leaf like bugs

#8  Postby CJ » Dec 26, 2010 7:07 pm

:popcorn:
What star sign are you? Please tick you star sign in a tiny bit of ongoing research. :)
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Re: Leaf like bugs

#9  Postby Spearthrower » Dec 27, 2010 8:54 pm

Passer wrote:Concerning evolution, how does it explain the bug that changes itself to look like a leaf? Does it explain it the same way as other forms of life? I've heard tell of a butterfly or more probably a moth, I can't quite remember now, but it evolved into two different types. One type, because it spends its time mostly in rural areas, is white in colour, but the other type, because it spends most of its time in and around a dirty industrialised area, is more grey in its colouring.

But the bug resembling a leaf seems a bit of a stretch.


http://en.wikipedia.org/wiki/Peppered_moth_evolution

The peppered moth study provides an example of natural selection through predation and camouflage. The observed shift in colouration happened over just a few generations. Leaf-shaped insects are the same principle over many, many more generations.

There are thousands of examples, some well known ones here:

http://en.wikipedia.org/wiki/Mimicry

If you don't think natural selection can produce mimicry, can you suggest an alternative?
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Re: Leaf like bugs

#10  Postby Passer » Dec 27, 2010 9:09 pm

I find this fascinating!

EDIT: Thank you all
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Re: Leaf like bugs

#11  Postby susu.exp » Dec 31, 2010 9:04 pm

It´s worth noting that bugs are insects belonging to the Hemiptera, whereas leaf insects belong to a group called Euphasmida. They are distantly related, but their most recent common ancestor was at the base of the Neoptera. Butterflies and Beetles have a closer relationship than that. It bugs me (no pun intended) sometimes, that people don´t check these things with insects first. Imagine somebody writing a thread called "huge bat swimming the ocean feeding on krill", asking how evolution allowed a bat to swim through the ocean feeding on krill and meaning blue whales. They aren´t bats of course, but both bats and whales are mammals. Calling Phasmids bugs isn´t that different (it´s just a group that we aren´t as much involved as as mammals, but making up most of metazoan diversity should count for something).
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Re: Leaf like bugs

#12  Postby Sityl » Dec 31, 2010 11:48 pm

susu.exp wrote:It´s worth noting that bugs are insects belonging to the Hemiptera, whereas leaf insects belong to a group called Euphasmida. They are distantly related, but their most recent common ancestor was at the base of the Neoptera. Butterflies and Beetles have a closer relationship than that. It bugs me (no pun intended) sometimes, that people don´t check these things with insects first. Imagine somebody writing a thread called "huge bat swimming the ocean feeding on krill", asking how evolution allowed a bat to swim through the ocean feeding on krill and meaning blue whales. They aren´t bats of course, but both bats and whales are mammals. Calling Phasmids bugs isn´t that different (it´s just a group that we aren´t as much involved as as mammals, but making up most of metazoan diversity should count for something).


Thanks for the info. Can you give us any idea of how long ago the Neopterian split between bugs proper and stick "bugs" happened? How long ago did bats and whales split? I know these will be rougher estimates based on available data, but it seems like if we had rough timelines these things would be easier to grasp.

By the way, for those who don't know what a "Neoptera" is,

http://en.wikipedia.org/wiki/Neoptera

They're basically all winged insects who can flex their wings over their abdomen, including earwigs, cockroaches, grasshoppers, termites, mantises, lice, ants, bees, beetles, fleas, butterflies, and moths. So it seems that it's a quite large classification.
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Re: Leaf like bugs

#13  Postby susu.exp » Jan 01, 2011 1:27 am

Well, the basic splits in the Neoptera occured in the late devonain, about 350 million years ago. At this time the Neoptera split into two groups - the polyneoptera which includes Phasmids and a lineage that would later split into the paraneoptera and the holometabola. The paraneoptera includes true bugs. The fossil record for Phasmids goes back to the early triassic (240Ma ago), that for true bugs to the earliest permian (295Ma ago) - Ages and Phylogeny from Grimaldi&Engel (2005).
Using Bininda-Emonds (2007) for the mammals I get a divergence between the groups including bats and whales at about 90Ma ago.

And yea, the Neoptera are pretty big - the only winged insects less close related to bugs than Phasmids are Dragonflies (Odonata) and Mayflied (Ephimeoptera). There are a lot of groups that are closer to Phasmids than to the Hemiptera though - the Polyneoptera also includes roaches, crickets, termites, mantisses, stone flies and earwigs (to name well knwon groups). Of the ones you named, lice are the closest to true bugs, the remaining ones are holometabolans.
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Re: Leaf like bugs

#14  Postby Delvo » Jan 01, 2011 4:42 am

Just because some silly entomologist at some point in the past decided to insist on pretending that the word "bug" has such an absurdly narrow definition, and somehow got other pretentious entomologists to go along with that obvious pretense, does not mean that that insistence has anything to do with the actual, and much wider, meaning of the word "bug" in the real world.
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Re: Leaf like bugs

#15  Postby Darwinsbulldog » Jan 01, 2011 9:22 am

An article by Eric Davidson & Douglas Erwin here: http://www.sciencemag.org/content/311/5762/796.abstract shows the relationships between changes in Gene Regularity Networks and changes in body form. Thus there is a relationship between phylogeny and form.
ABSTRACT:
Development of the animal body plan is controlled by large gene regulatory networks (GRNs), and hence evolution of body plans must depend upon change in the architecture of developmental GRNs. However, these networks are composed of diverse components that evolve at different rates and in different ways. Because of the hierarchical organization of developmental GRNs, some kinds of change affect terminal properties of the body plan such as occur in speciation, whereas others affect major aspects of body plan morphology. A notable feature of the paleontological record of animal evolution is the establishment by the Early “Cambrian of virtually all phylum-level body plans. We identify a class of GRN component, the kernels” of the network, which, because of their developmental role and their particular internal structure, are most impervious to change. Conservation of phyletic body plans may have been due to the retention since pre-Cambrian time of GRN kernels, which underlie development of major body parts.


http://sansan.phy.ncu.edu.tw/~hclee/SB_course /0709/A1_Gene_Regulatory_Networks_and_the_Evolution_of_Animal_Body_Plans.pdf

What D and E define as evolutionarily stable GRN "kernels" do not change over vast periods of evolutionary time, but "plug-ins" can change quite readily at species level and below. This means that various signaling pathways can influence end-of-development regulation of the structural genes. [Structural genes are those which produce "building proteins", such as muscle proteins, connective tissue etc in particular parts of tissues of the body.
Thus the bug, insect or indeed anything else can be selected on it's basis as a mimic of another creature [as in Bayesian Mimicry] or to resemble a twig. Obviously a bug that gets eaten because it is not well camouflaged will not be able to pass it's genes on. Those that do have developmental changes that make it a little better at camouflage will have a chance at passing it's modified structure on to the next generation. If this modified GRN subsystem [which defines the new shape during development] becomes fixed in the population due to it's higher fitness value, then it will become a permanent change.

Hox genes and their friends define the four-dimensional geometry of the developing embryo. Heterochronic changes of Hox gene expression of particular tissues or parts can lead to quite profound-looking changes in the animal's body shape.
These changes might occur initially as frequency dependent polymorphism.

In Dung Beetles, for example, there is sexual dimorphism in horn expression. Males have horns and females don't. Thus the sex determination pathways feed into the developmental networks that control gene expression for horns. But there is also hormonal pathways and insulin signaling pathways that can influence horn development also. So we can get size dimorphism between males based on insuin levels, which are in turn, determined by the size of the dung-ball that the mother beetle lays her egg in. Big balls of shit produce horned males, and smaller balls of poo produce hornless males:-

Emlen, D. J. and H. F. Nijhout (1999). "Hormonal control of male horn length dimorphism in the dung beetle Onthophagus taurus (Coleoptera: Scarabaeidae)." Journal of Insect Physiology 45(1): 45-53.
Male dung beetles (Onthophagus taurus) facultatively produce a pair of horns that extend from the base of the head: males growing larger than a threshold body size develop long horns, whereas males that do not achieve this size grow only rudimentary horns or no horns at all. Here we characterize the postembryonic development of these beetles, and begin to explore the hormonal regulation of horn growth. Using radioimmune assays to compare the ecdysteroid titers of horned males, hornless males, and females, we identify a small pulse of ecdysteroid which is present in both hornless males and females, but not in horned males. In addition, we identify a brief period near the end of the final (third) larval instar when topical applications of the juvenile hormone analog methoprene can switch the morphology of developing males. Small, normally hornless, males receiving methoprene during this sensitive period were induced to produce horns in 80% of the cases. We summarize this information in two models for the hormonal control of male dimorphism in horn length.

http://dbs.umt.edu/research_labs/emlenl ... .%2099.pdf

Thus these bugs are adaptable to variable food availability. So long as the food availability is cyclic, this polymorphism will persist. But speciation can occur if one form is favoured over another. See this paper on lizard polymorphism:-

Corl, A., A. R. Davis, et al. (2010). "Selective loss of polymorphic mating types is associated with rapid phenotypic evolution during morphic speciation." Proceedings of the National Academy of Sciences 107(9): 4254-4259.
Polymorphism may play an important role in speciation because new species could originate from the distinctive morphs observed in polymorphic populations. However, much remains to be understood about the process by which morphs found new species. To detail the steps of this mode of speciation, we studied the geographic variation and evolutionary history of a throat color polymorphism that distinguishes the “rock-paper-scissors” mating strategies of the side-blotched lizard, Uta stansburiana. We found that the polymorphism is geographically widespread and has been maintained for millions of years. However, there are many populations with reduced numbers of throat color morphs. Phylogenetic reconstruction showed that the polymorphism is ancestral, but it has been independently lost eight times, often giving rise to morphologically distinct subspecies/species. Changes to the polymorphism likely involved selection because the allele for one particular male strategy, the “sneaker” morph, has been lost in all cases. Polymorphism loss was associated with accelerated evolution of male size, female size, and sexual dimorphism, which suggests that polymorphism loss can promote rapid divergence among populations and aid species formation.

Of course, I have said very little about camouflage and mimicry directly, because I think my example of dung beetle horn dimorphism illustrates how flexible gene regulatory networks are in producing drastic changes in morphology within a single species, or indeed, a single sex by receiving inputs from sex and hormonal signaling pathways.
The literature on "camouflage" and "mimicry" is vast, and some basic google searches turns up lots of hits. Ad "Hox" to the search and one will get entries like this one:-

Wittkopp, P. J. and P. Beldade (2009). "Development and evolution of insect pigmentation: Genetic mechanisms and the potential consequences of pleiotropy." Seminars in Cell & Developmental Biology 20(1): 65-71.
Insect pigmentation is a premier model system in evolutionary and developmental biology. It has been at the heart of classical studies as well as recent breakthroughs. In insects, pigments are produced by epidermal cells through a developmental process that includes pigment patterning and synthesis. Many aspects of this process also impact other phenotypes, including behavior and immunity. This review discusses recent work on the development and evolution of insect pigmentation, with a focus on pleiotropy and its effects on color pattern diversification.


Or this:-

http://www.plosone.org/article/info%3Ad ... ne.0004035

Rubinoff, D. and J. J. Le Roux (2008). "Evidence of Repeated and Independent Saltational Evolution in a Peculiar Genus of Sphinx Moths (Proserpinus: Sphingidae)." PLoS ONE 3(12): e4035.
Background: Saltational evolution in which a particular lineage undergoes relatively rapid, significant, and unparalleled change as compared with its closest relatives is rarely invoked as an alternative model to the dominant paradigm of gradualistic evolution. Identifying saltational events is an important first-step in assessing the importance of this discontinuous model in generating evolutionary novelty. We offer evidence for three independent instances of saltational evolution in a charismatic moth genus with only eight species.Methodology/Principal FindingsMaximum parsimony, maximum likelihood and Bayesian search criteria offered congruent, well supported phylogenies based on 1,965 base pairs of DNA sequence using the mitochondrial gene <italic>cytochrome oxidase subunit I, and the nuclear genes <italic>elongation factor-1 alpha</italic> and <italic>wingless</italic>. Using a comparative methods approach, we examined three taxa exhibiting novelty in the form of Batesian mimicry, host plant shift, and dramatic physiological differences in light of the phylogenetic data. All three traits appear to have evolved relatively rapidly and independently in three different species of <italic>Proserpinus. Each saltational species exhibits a markedly different and discrete example of discontinuous trait evolution while remaining canalized for other typical traits shared by the rest of the genus. All three saltational taxa show insignificantly different levels of overall genetic change as compared with their congeners, implying that their divergence is targeted to particular traits and not genome-wide.Conclusions/Significance Such rapid evolution of novel traits in individual species suggests that the pace of evolution can be quick, dramatic, and isolated—even on the species level. These results may be applicable to other groups in which specific taxa have generated pronounced evolutionary novelty. Genetic mechanisms and methods for assessing such relatively rapid changes are postulated.


While there is no doubt that some evolution is gradual and achieved in small steps, each of which must confer fitness and is historically contingent on previous innovations, it is also clear that saltational stepping [large changes to morphology and even speciation] can occur via relatively minor genetic change. In the light of such successful rather than merely hopeful monsters that can be produced via the seemingly paradoxical properties in Gene Regulatory Networks of both high conservation and great evolvability and flexibility to respond to environmental challenges via signaling pathway inputs into those GRN's, then the evolution of mimicry seems like child's play.
That GRN's can produce such stability and innovation is based, as Davidson and Erwin suggest, is because GRN's are nested and hierarchical. Changes very early in development are almost always fatal, but late changes in development are not.
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Re: Leaf like bugs

#16  Postby susu.exp » Jan 01, 2011 1:33 pm

Delvo wrote:Just because some silly entomologist at some point in the past decided to insist on pretending that the word "bug" has such an absurdly narrow definition, and somehow got other pretentious entomologists to go along with that obvious pretense, does not mean that that insistence has anything to do with the actual, and much wider, meaning of the word "bug" in the real world.


You got your history wrong. The word bug first appears in English texts in the 17th century and remained restricted to animals within the hemiptera for a long time. The "silly entomologist" was von Linne who gave the technical name in the 10th revised Edition of the "Systema Naturae" in 1758. A broader non-technical use entered american english in the 19th century, but biological sciences have not seen a good reason to change their technical use. In particular since that broader use is mostly restricted to the Americas.
To check for the usage, let´s turn to Darwin. In the Origin he refers to the proboscis of the bugs, noting that it is "curious[ly] folded", indeed a synapomorphy of the hemiptera. In "Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the command of Capt. Fitz Roy", Darwin Describes the a bug, which again, is a member of the Heteroptera (genus Reduvius). In "The variation of plants and animals under domstication", he again refers to a Hemipteran as a bug.
Try as you might, you won´t find uses of bug for anything non-Hemipteran in biological science, nor in older text, nor in a lot of texts that aren´t american.
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Re: Leaf like bugs

#17  Postby HAJiME » Jan 01, 2011 1:52 pm

Sityl wrote:
Passer wrote:Concerning evolution, how does it explain the bug that changes itself to look like a leaf? Does it explain it the same way as other forms of life? I've heard tell of a butterfly or more probably a moth, I can't quite remember now, but it evolved into two different types. One type, because it spends its time mostly in rural areas, is white in colour, but the other type, because it spends most of its time in and around a dirty industrialised area, is more grey in its colouring.

But the bug resembling a leaf seems a bit of a stretch.


This is a good question, Passer, and I don't think anyone could do as good of a job at explaining it than Carl Sagan. Please watch this video, it's short but spot on.

[youtube]http://www.youtube.com/watch?v=dIeYPHCJ1B8[/youtube]

I LOVE this story of the crab! Thanks for sharing.
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Re: Leaf like bugs

#18  Postby NineBerry » Jan 01, 2011 3:11 pm

bug (n.)

"insect," 1620s (earliest reference is to bedbugs), probably from M.E. bugge "something frightening, scarecrow" (late 14c.), a meaning obsolete except in bugbear (1570s) and bugaboo (q.v.); probably connected with Scot. bogill "goblin, bugbear," or obsolete Welsh bwg "ghost, goblin" (cf. Welsh bwgwl "threat," earlier "fear"). Cf. also bogey (1) and Ger. bögge, böggel-mann "goblin." Perhaps influenced in meaning by O.E. -budda used in compounds for "beetle" (cf. Low Ger. budde "louse, grub," M.L.G. buddech "thick, swollen"). Meaning "defect in a machine" (1889) may have been coined c.1878 by Thomas Edison (perhaps with the notion of an insect getting into the works). Meaning "person obsessed by an idea" (e.g. firebug) is from 1841. Sense of "microbe, germ" is from 1919. Bugs "crazy" is from c.1900.


http://www.etymonline.com/index.php?sea ... search=bug
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Re: Leaf like bugs

#19  Postby susu.exp » Jan 01, 2011 7:19 pm

The problem is that there´s no reference to a more general use as a synonym for insect - bedbugs are Hemipterans, and the two species of insects I can think of that have common names containing bug while not being Hemipterans go back to the 19th century and are noted to have originated in the southern US.
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Re: Leaf like bugs

#20  Postby Berthold » Jan 20, 2011 7:31 pm

Passer wrote:But the bug resembling a leaf seems a bit of a stretch.

I suppose you are another victim of that old canard, "How useful can be half of a [insert trait or body part]?"

Indeed, an imperfect camouflage is useful: Under conditions of bad sight, or when the predator is in a hurry, or has already eaten a bit... And so it goes on, with every slight modification favoured if it means an ever so slight advantage. Until the animal gets to a stage where even the best-sighted predator has a hard time finding it even though it sits right under the predator's nose. :grin:
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