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  Topic: Coloration of animals, mimicry, aposematism, Is really natural selection behind it?< Next Oldest | Next Newest >  
VMartin



Posts: 525
Joined: Nov. 2006

(Permalink) Posted: Oct. 15 2007,15:14   

Quote

The spiders mimic ants, which keeps most insectivore predators away.


This is only an unproved pressuposition. It is not as clear as it is presented, it is no way  "eternal truth". Do you have any links, any evidence? The same authors you quoted have written also about Myrmarachne another article:

"Out of the Frying Pan and into the Fire: a Novel Trade-Off for Batesian Mimics".

So you can see the problem is more complicated and I would say unresolved yet. There should have been very strong selective pressure driving some spiders towards ants and to look like them.

As to the article itself: some displaying Myrmarachne were eaten neverthenless. Some of them didn't display at all. One should ask - why some individuals didn't display? Individuals that don't display should have been
already eradicated by natural selection. Why they survived, having no reflex when dangerous Salticidae is stalking? Btw. as far as I can judge this experiment has researched something never observed outside, it only wants to prove a hypothesis. Quoting: "...but there are, besides several hundred records of ant-eating salticids eating ants, 14 records of ant-eating salticids eating ant-like salticids". I suppose no displaying Myrmarachne was observed in coutryside.  

The validity of these indoors experiments can be better showed in another reserach done by the same authors:

"Living with the enemy: jumping spiders that mimic weaver ants".

There they put together for 10 hours weaver ants with Myramachne assimilis and different individuals representing Myrmecophagic, Myrmecomorphic, Myrmecophilic and ordinary species . Oddly enough when 40 ants were present  "few salticids survived when confined with groups of 40 ants, regardless of category".

The problem is that all those species in countryside survive very well, even in anthills. So I do not see a point of these researches, except to prove "mimicry"  
in artificial conditions. Results of these experiments sometimes contradicts reality outdoors - but proved "mimicry" as conceived in armchairs of Universities.
All tested species couldn't have acquired any host-specific cuticular hydrocarbons, because individuals used never encountered ants before being tested. The scientists researched if "M. assimilis might have evolved adaptations that make it especially proficient at surviving in the presence of it model even in the absence of opportunity to acquire nest-mates cues."



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Another problem is probably division on Myrmecophagic, Myrmecomorphic and Myrmecophilic species. The pre-war German school used different categorization of ant "mimics". We should be aware that also myrmecomorphic probably have to be myrmecophilic (and that's why the whole article the poor Erasmus has given link to should be discussed more deeply) because - according the same authors - "Batesian mimics of ants may be forced to "walk a tightrope", living with the "enemy". They need to be close to the model for safety from other predators but at the same time need to avoid becoming the model prey".

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And last but not at least : Heikertinger sometimes repeated such experiments and obtained totally different results. See EvC where admin asked me to traslate it from German. He had made the same experiments with ladybirds and their "victims" as selectionists made. But  I don't claim that the mentioned experiments with ants and spiders are are wrong. Just for a record.

Anyway there are pletny of birds' species that eat ants and it is not sure that being ant's "mimic" is some advantage even though darwinists claim: of cource, it is.

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I could not answer, but should maintain my ground.-
Charles Darwin

  
  365 replies since Sep. 21 2007,11:31 < Next Oldest | Next Newest >  

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