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Author Topic:   Mimicry: Please help me understand how
Modulous
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Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 10 of 241 (411669)
07-21-2007 7:06 PM
Reply to: Message 7 by Chiroptera
07-19-2007 8:43 AM


Further to that Dawkins reminds states:
Ledyard Stebbins did a theoretical calculation about an extremely weak selection pressure, acting on a population of mouse-sized animals to favor the largest individuals. His hypothetical selection pressure was so weak as to be below the threshold of detectability in field sampling studies. Yet the calculated time to evolve elephant-sized descendants from mouse-sized ancestors was only a few tens of thousands of generations... Worse, Stebbins's calculation assumed an exceedingly weak selection pressure. The real selection pressures measured in the field by Ford and his colleagues on lepidoptera and snails, by Endler and his colleagues on guppies, and by the Grants and their colleagues on the Galapagos finches, are orders of magnitude stronger. If we fed into the Stebbins calculation a selection pressure as strong as the Grants have measured in the field, it is positively worrying to contemplate how fast evolution could go.
If the selection pressure to be a little less conspicuous to birds is so slight as to be unnoticeable to biologists...it could still result in quick and radical changes.

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Modulous
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Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 16 of 241 (413972)
08-02-2007 4:22 AM
Reply to: Message 13 by MartinV
08-01-2007 4:00 PM


more or less
Wasps have many bird's predators who eat them.
I'm willing to bet that lepidoptera has more predators than vespa/vespidae. This is doubly backed up by the fact that bee-eaters also eat moths anyway. I think it should be fairly apparant that reducing the number of potential predators conveys a significant advantage.
Edited by Modulous, : No reason given.

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 19 of 241 (414007)
08-02-2007 10:23 AM
Reply to: Message 18 by MartinV
08-02-2007 9:51 AM


mimicry isn't the problem, then
I wouldn't bet. Such a conclusion follows only from darwinistic explanation of mimicry.
Or one could just apply reason and examine evidence. Bees only have to worry about bee-eaters, whereas moths have to worry about bee-eaters and other birds. The set that contains both bee-eaters and other birds is either the same size as, or bigger than the set that just contains bee-eaters.
The evidence shows us that the set of bee-eaters n other birds is bigger than just bee-eaters. It could be shown to be false with closer examination but there is no need to appeal to Darwinism.
Now you suggest further study is required, and that's fine. Further study is always required, and entomologists have a lot of work to do!
If it turns out that looking like a wasp does not deter predation, why even consider mimicry? Why not just point to wasps and ask what explanation is there for their markings?

No - I don't believe a cosmic Jewish zombie can make me live forever if I eat his flesh and telepathically tell him that I accept him as my master, so he can then remove an evil force from my soul that is present in all of humanity because a dirt/rib woman was convinced by a talking snake to eat from a magical tree about 6,000 years ago just after the universe was created. Why should I?

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 24 of 241 (414192)
08-03-2007 6:35 AM
Reply to: Message 23 by MartinV
08-03-2007 5:21 AM


Re: mimicry isn't the problem, then
The problem of the so-called mimicry had been studied very thoroughly before second WW in Germany.
I'd prefer the post WWI stuff, you refer to a paper in 1903 which came a long time before the modern synthesis.
In the described process natural selection plays no role.
So? The Modern Synthesis does not require that all evolutionary events are the sole result of natural selection, and that includes colouration. Mimicry is more than just having similar colouration, of course, and I'd be surprised if you can find a good reason for some of the more elaborate mimics that did not require some reference to natural selection. I'd urge you to pick papers from after the discovery of genetics and the synthesis of same with other evolutionary mechanisms.
Also, the paper you refer is much longer than the single page you posted, so we'd need to read the whole thing before coming to any conclusions, no?
Finally, I don't see any mechanisms proposed here - just the changing of patterns throughout a lizards life being described - perhaps you'd like to fill me in?

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 44 of 241 (418254)
08-27-2007 5:53 AM
Reply to: Message 34 by MartinV
08-23-2007 3:35 PM


Re: mimicry isn't the problem, then
That does not seem to have any relevance to anything I said. You raise the point that most mimicry is not perfect which I agree with. That is nothing to do with the fact that mimicry is more than just having similar colouration and the challenge to explain other mimics with 'transformation rules' rather than natural selection.

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 88 of 241 (424580)
09-27-2007 2:18 PM
Reply to: Message 87 by MartinV
09-27-2007 1:14 PM


stings and the taste of venom
All of you are like broken records here. So again: stings play no role
OK, stings play no role:
quote:
Only two of their birds were stung; the others avoided eating bumblebees only after having eaten the “middle segments of the abdomen”, presumably with the venom sac. In this case unpalatability may be due to distasteful venom
The reasons birds avoid eating bumblebees might be because they ate the venom, not because they get stung trying. It goes on to say
quote:
When tasted or eaten, honeybees induced the same unpalatability reactions as for wasps (see below), but these were more limited in degree, and appeared less frequently. Using mealworms smeared with abdominal tissues, Mostler showed that unpalatability was the main cause of the rejection response. As in the case of wasps, Liepelt (1963) demonstrated the bad taste of the abdomen derived from the venom. The removal of the entire sting apparatus including the venom sac rendered honeybees completely palatable, and all were eaten.
And about wasps:
quote:
It is the terrible taste that the venom imparts to the abdomen that is the main deterrent for birds.
The paper also states:
quote:
These established beyond doubt that the colour patterns of all the syrphids he used did give substantial protection from predation, and that the protective effect was proportional to mimetic similarity (Figs 1 & 2). Honeybees and their mimics were a less successful mimetic system than the wasp system, while the bumblebee system was the most successful of all. When mimics were offered soon after their models (within 50 mins) in the wasp mimicry system, the wasp mimics were strongly protected (Fig 2), fading with time, but this protection vanished when they were offered before models, and in fact the wasps suffered, since more wasps than normal were attacked.
Fascinating stuff.
Edited by Modulous, : No reason given.

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 Message 87 by MartinV, posted 09-27-2007 1:14 PM MartinV has replied

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 Message 89 by MartinV, posted 09-27-2007 2:51 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 90 of 241 (424598)
09-27-2007 4:18 PM
Reply to: Message 89 by MartinV
09-27-2007 2:51 PM


Re: stings and the taste of venom
as an unbiased man you probably see the difference between birds in countryside and birds held in cages. Stressed birds or birds full of unnatural meal in cages, birds that are often feeded in the same time and consequently do not prey, such birds have different feeding patterns as in free. Do you agree?
It is certainly feasible. I'd want to see studies that show the degree of difference before committing further. I'd also need to see the conditions the birds in the experiments mentioned were in to see if they would be subject to this phenomenon.
That said, it is still an important observation that some birds do have the ability to discriminate when it comes to noxious insects (ie., if they eat the non-noxious mimic first, they tend to also attack the noxious model but if they eat the noxious model first, they tend to avoid the mimic). It would be odd to think that birds developed this specific behaviour as a result of captivity stress.
The most important are experiments outdoors and from those are the most important studies of the content of stomachs of real birds.
They may be important. What they don't tell us, unfortunately, is whether birds learn to avoid certain prey over time (unless we tag them I guess - has that been done?).
These experiments was done by Biological Survey Division of United States Department of Agriculture. They wanted to estimate harmfulness of birds. These results are neglected by selectionists, because they show something selectionists do not like - wasp, bees are readily eaten by birds.
I've not seen them, so I couldn't say either way.
All I see there that is conclusive is that some birds have a big impact on parasitic hymenoptera. They are the ones that don't have the yellow/black colouration hypothesized to be a warning. Perhaps you have more information on this paper?
Again, what species of wasp?
Another point of note, is that some birds have been known to discriminate between wasp gender - which is yet another thing to keep in mind. The thing is, it is difficult to falsify the hypothesis by looking at a small number of species.
Edited by Modulous, : No reason given.

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 96 of 241 (426197)
10-05-2007 4:35 PM
Reply to: Message 91 by MartinV
10-05-2007 3:42 PM


Re: Wasps and their "mimics"
On the other hand, all the syrphids were considered to be palatable, and even the superb wasp mimic Temnostoma vespiforme was eaten by Spotted Flycatchers despite the fact that its model was rejected. Dlusski concluded that these experienced birds usually distinguished between models and mimics, even the good ones, and thus mimicry was ineffective here.
Indeed, and it goes on to say:
quote:
I can summarise the available data no more clearly than Steiniger (1937b) did many years ago:
” syrphids form part of the normal dipteran diet of many insectivorous birds such as Robins (Erithacus rubecula), Redstarts, and Sylvia and Phylloscopus warblers;
” wasps are not normal food for these birds, which do not have any innate avoidance of wasps, and eventually come to try one; once tried, they are not eaten any more;
” syrphids are also removed from the normal diet of these insectivores as soon as they become acquainted with wasps, since wasps and syrphids are apparently confused.
” The protective effects of this process are related to the similarity between model and mimic, but even poor quality mimics benefit to some degree.

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 Message 91 by MartinV, posted 10-05-2007 3:42 PM MartinV has replied

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 102 of 241 (426356)
10-06-2007 8:08 AM
Reply to: Message 98 by MartinV
10-05-2007 9:54 PM


Re: Wasps and their "mimics"
I don't see what "available data" about syrphids the autor wanted to summarize.
As difficult as it sounds, you could try reading the data he author wanted to summarize:
quote:
Apart from Mostler’s and Dlusski’s work, there are really only fragments of information in the literature about the protective effects of syrphid mimicry (see Pocock, 1911; Lane, 1957; Steiniger, 1937a,b; Liepelt, 1963; Davies & Green, 1976; Heal, 1982, 1995; Evans & Waldbauer, 1982; Evans, 1984; Grewcock, 1992). I can summarise the available data no more clearly than Steiniger (1937b) did many years ago
Field-based data shows (Csiki, McAtee, see my above posts)clearly that stomachs of many different birds contain wasps.
Not entirely relevant. Nobody is saying that birds don't eat wasps. What we are saying is that certain types of wasps will be avoided after being eaten by certain types of bird. If I recall correctly I pointed out that some of your references were talking about parasitic wasps. Parasitic wasps don't generally have the warning colouration of their yellow-jacketted cousins.
A Wasp. source Obviously this wasp will not be protected against bird predation based on its colours, so if birds happened to be eating a lot of them, it makes no difference to the concepts of mimicry.
You need to explain all of the data, not just selected snippets. I suspect you cannot. The paper you reference the most is a fascinating look at the subject, have you tried reading the entire thing?

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 Message 98 by MartinV, posted 10-05-2007 9:54 PM MartinV has replied

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 Message 103 by MartinV, posted 10-06-2007 4:14 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 104 of 241 (426490)
10-07-2007 5:14 AM
Reply to: Message 103 by MartinV
10-06-2007 4:14 PM


Re: Wasps and their "mimics"
The paper deals predominatly with hoverflies mimics, Syrphidae. There are 6.000 species in 200 genera in this family. Either all six thousands species mimic wasps or there is a line where some species are mimicking wasps and others are not. Because author obviously considers hoverflies to be mimic he faced contradicting theories of "imperfect" mimicry and utterly hypothetical forces that hinder perfection of "imperfect" mimicry.
The more simple solution would be accept an idea there is no micry of hoverflies at all. The similarity is pure coincidence of coloration of two animals groups.
I don't see that in the paper. I see the mimicry theory supported by the paper with reference to an unfortunate lack of work on the subject.
There are many facts supporting the idea that birds eat wasps readily, so selective force to their mimics is very dubious on my view.
The question remains, do all birds eat yellow-jacket wasps readily after eating them the first time? The evidence demonstrates that some birds will avoid eating wasps, and their mimics, after eating a wasp. That is the evidence you need to deal with.
Your studies also suffer from the same issue that you have not addressed yet. Not all wasps and bees have distinctive yellow jackets. Your studies do not tell us if the subfamily was mostly vespinae (yellow-jackets) or polistinae (often brown) nor does it do likewise for bees - we cannot rule out Xylocopines. Since the studies you cite do not provide this kind of detail they cannot be used to draw absolute conclusions. Even if we were to draw those conclusions the fact that some birds eat yellow-jackets is not evidence that yellow-jackets do not enjoy some protection from predators.
I suspect you are unable to see this.
Birds attack also bird nests
Hardly relevant, but what you meant to say was they attack wasp and bee nests. Yes, some of them do. I've not disputed this fact, and indeed entered this fact into the debate myself - so I'm unsure what you think your point is. I suspect that you think that because some birds attack some wasps, that is evidence that wasps' visual pattern is not a deterrent. In some cases it isn't, but it doesn't need to be for it to provide a selective advantage.
The carton nests of the polistine wasps, Polybia occidentalis and P. barbouri, are frequently destroyed by predators feeding on wasp brood in northwestern Costa Rica.
As noted, polistinae are not quite as distinctive as yellow jackets. But I have already put forward information regarding the attacking of nests. Some do it for the nest itself, others for the grubs, and some for the wasps themselves.
This is not evidence that yellow-jackets offer some protection, but again you probably don't see that. I seem to remember putting this very paper forward, not very long ago. Here is the section I referred to:
quote:
Possibly the scarcity of attacks is due to the
ability of social wasps to defend themselves so
that relatively few species of birds are able to
ingest them. Similarly there seem to be few avian
attacks on caterpillars of the family Arctiidae
(which includes the Ctenuchinae). Many species
of moths of this family sequester alkaloids from
their host plants which results in the caterpillar
being impalatable to potential predators (Watson
1975). An additional variable to be considered in
gaining an understanding of avian predation on
noxious insects is the ability of individual birds
to learn how to process a prey item prior to
ingestion. Such behaviour results in big differences
in the species of insects taken -even among
individuals of a particular species of bird. Sometimes
a bird learns to recognize particular types
of insects and is able to manipulate the prey so
as to avoid the insect's defense system (Brown &
Vasconcelos 1976). A bird can also learn to recognize
a particular sex of an insect species. For
example, one White- throated Kingbird (Tyrannus
albogularis caught and ate numerous male of
the solitary bee (Epicharis melanoxantha Moure),
but was never seen to capture a female though the
males have a faster, erratic flight (Raw 1992, in
press).
Which would indicate, once again, that some birds find wasps noxious and develop strategies to overcome the wasps' defence. As we have seen, there are several strategies possible here. Avoid wasps and insects that look like wasps. Or, avoid eating the noxious poison sacs of wasps. The former is easier - but the latter is potentially more rewarding.

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 Message 105 by MartinV, posted 10-09-2007 3:28 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 106 of 241 (427076)
10-09-2007 4:34 PM
Reply to: Message 105 by MartinV
10-09-2007 3:28 PM


Heikertinger
Heikertinger is also mentioned in the article as "source" but oddly enough no one of his idea has been dealt or mentioned in the article!
It really shows that you haven't read it, or even bothered to do a search:
quote:
An obvious tack is to deny that mimicry can possibly be of poor quality, and hence to claim that poor ”mimics’ simply are not mimics at all. Before the advent of more rigorous quantitative testing of mimicry theory by the Browers and others, there were several who claimed that because some mimics were eaten by some predators sometimes, this meant that mimicry did not ”work’, and hence was invalid as a theory (McAtee, 1932; Heikertinger, 1918, 1936, 1954). It is a simple step then to accept perfect mimicry as a valid concept, but to deny any other kind of resemblance as mimetic: for example, Glumac (1962) and Drees (1997) thought there were no mimics among syrphids except for those with elongated antennae (even bumblebee mimics, which they attributed to convergent requirements of thermoregulation). Waldbauer and his colleagues (see Waldbauer, 1988; Maier, 1978) simply ignored poor mimics altogether because it was impossible to determine whether they were really mimics or not.
However, denial of the reality of mimicry in these syrphids has not been credible since Mostler’s (1935) detailed and large-scale experiments on learning in nave and experienced insectivorous birds. Single birds were free to fly in a large windowed room with naturalistic perches, and models and mimics were released alive into the back of the room, usually to fly directly to the window: Mostler recorded the subsequent behaviour of the birds. He divided his study into two parts: the first was concened with the beginning and the end points of the learning of birds, i.e. the responses of young nave birds and of old experienced birds to models and mimics; the second part investigated the learning process itself. Although he did not plot or hardly even analyse his data, the great value of his work is not just that it was the first well-designed large-scale experimental approach to testing the theory of mimicry, but also that he obtained comparable data on all three hymenopteran models and their hoverfly mimics. These established beyond doubt that the colour patterns of all the syrphids he used did give substantial protection from predation
The section I bolded (and the ones before) seems to be an accurate summing up of your argument, and since you are arguing based on Heikertinger and McAtee I assume it is an accurate summing up of their argument too. Heikertinger was mentioned, and his idea was dealt with.
But the question is like this - if there are species, that are more cryptic like bees or species in polistinae - why are they not protected by "aposematism"? They do not need it? But vespinae need it?
You could ask the same question of any flying insect - why don't they all have aposematism? Evidently it is not required that a flying insect evolves aposematism, but it can happen.
I am afraid the research done on 80.000 contents of stomach birds showed clearly that wasps are eaten by birds and it were these facts that persuaded McAtee that aposematism of birds is ineffective.
I'm not claiming that birds do not eat wasps.
Do not forget there are 600 species of moth's family that possess yellow-black striped patterns and we should consider probably also those species as mimics.
There are also dragonflies with black-yellow patterns etc...
Maybe yellow-black patterns are so common in insect realm that we shouldn't consider it as mimicry especially when results of experiments of protective value of "model" are so ambiguous and often contradicting each other.
Yes - yellow/black is certainly a possible colour an insect might possess. It doesn't have to serve as aposematism in all cases - I really haven't looked. I have not seen evidence that the experiments regarding protective value were ambiguous. Field observation and experiments have clearly shown that some birds avoid mimics after they have had a negative experience with a noxious model.

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 Message 105 by MartinV, posted 10-09-2007 3:28 PM MartinV has replied

Replies to this message:
 Message 107 by MartinV, posted 10-10-2007 2:59 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 108 of 241 (427239)
10-10-2007 3:15 PM
Reply to: Message 107 by MartinV
10-10-2007 2:59 PM


Re: Heikertinger
It could be taken for granted that whatever aposematic or "poisonous" species you find there are almost for sure predators specialised on it. See many bee-eaters etc.
Such predators wellcome aposematism of wasps I dare say - they can see wasps from great distance.
No doubt. Do you suggest that the penalty for aposematism outweighs or balances out its benefits? Do you have any evidence for this?
As far as I can judge one of the most used explanation of aposematism is that it represents a warning - be carefull I am dangerous and remember me! I don't see a point to be dangerous and not to represent it as in the case of many species of wasps, bees, bumble-bees etc...
Not just dangerous but also distasteful. If you are dangerous you don't have to advertise it. Wasps that sting but don't warn about their bad taste can still use their sting to subdue prey or what have you. Not all wasps have stings as far as I am aware too.
It depends. Other experimets show that after few hours the stinged birds eat wasps as if nothing happened.
Right, but in total the data shows that some birds avoid eating some mimics after they have eaten a noxious model.
Yes. Scientists should perhaps reconsider "imperfect mimicry" of those 6.000 species of hoverflies. Maybe we are not facing mimicry but some kind of convergent evolution that has nothing to do with mimicry.
If there is reason to conclude that, then so be it.

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 115 of 241 (429197)
10-18-2007 7:48 PM
Reply to: Message 112 by garyl43
10-18-2007 7:08 PM


How did the orchid survive before it had the perfect mechanism to match this specific wasp?
...
In order for it to reproduce it had to have all this right the first time or it would have simply died out.
Other orchids survive just fine without this mechanism.

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 Message 112 by garyl43, posted 10-18-2007 7:08 PM garyl43 has replied

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 Message 116 by garyl43, posted 10-18-2007 7:55 PM Modulous has replied

  
Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 120 of 241 (429211)
10-18-2007 8:45 PM
Reply to: Message 116 by garyl43
10-18-2007 7:55 PM


That's one of my points Modulous. There is no need for this kind of complexity.
No, there isn't. There is no need for the earth to exist, for life to exist, or for life to look the way it does.
But there is an explanation for biodiversity, including mimics.

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Modulous
Member
Posts: 7801
From: Manchester, UK
Joined: 05-01-2005


Message 127 of 241 (433009)
11-09-2007 2:30 PM
Reply to: Message 126 by MartinV
11-09-2007 2:13 PM


Re: McAtee about "aposematism"
It seems you are repeating yourself. McAtee and Heikertinger have been discussed, and arguments as to why they might not have been right in their conclusions have been presented. Instead of repeating their conclusions, can you please deal with the subsequent argument?
Rule 4 partly writes:
Address rebuttals through the introduction of additional evidence or by enlarging upon the argument. Do not repeat previous points without further elaboration.

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 Message 126 by MartinV, posted 11-09-2007 2:13 PM MartinV has replied

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