It looks like there will be a bit of biology today, which is a relief to me (and maybe others) given the impending dissolution of our Republic. There are two quiz questions in this post; see if you can answer them in the comments.
I’ve posted a bit on Batesian mimicry, in which a noxious species (called the “model”) is avoided by a predator, often because it has bright colors or patterns that call attention to it (“aposematic coloration”). Models who are avoided by predators include bees, wasps, and some foul-tasting butterflies like the Monarch (see earlier post). When a predator has learned to avoid a particular pattern because it’s associated with toxicity or distastefulness—and this means that that predator has to have had at least one experience with the model to induce learning—this gives an evolutionary opening for a non-toxic or tasty species to evolve a resemblance to the model. These species, called “mimics”, experience selection for that resemblance because the more you resemble a model that’s already avoided by a predator, the greater chance you have of surviving and passing on your genes—thus enriching the mimic gene pool in those genes that make them look like models.
Here’s one example of Batesian mimicry (named after the naturalist Walter Henry Bates who described the phenomenon): the nestlings of the bird Laniocera hypopyrra, the “cinerous mourner” in Peru. This is bizarre because the baby birds resemble, both in behavior and appearance, a toxic caterpillar that lives in the same area. Read my post on this amazing resemblance. (This is not 100% confirmed as a case of Batersian mimicry, but it looks pretty good):
You can find my other posts on Batesian mimicry here.
The other classic form of mimicry is called Müllerian mimicry, named after the German biologist Fritz Müller, who described the phenomenon. In this case a number of distasteful, dangerous, or toxic species come to resemble each other because it facilitates predator learning. By that I mean that the more individuals of different species who have been sussed out as bad by predators come to resemble each other, the greater protection they’ll enjoy, as the different species with similar appearances will cause the predator to learn even more strongly. (Quiz question #1: given two toxic aposematic species that look different and are already avoided by predators, why would it be advantageous for a single mutant individual of one species to resemble members of the other species?)
In Müllerian mimicry, both species are models and mimics at the same time. There are lots of cases of Müllerian “mimicry rings” in which very unrelated species come to adopt similar colors and patterns: these rings can involve moths, beetles, butterflies, true bugs, and so on—all looking similar. They must, of course, live in the same place, for to evolve the system requires a predator that encounters all the species—just as in Batesian mimicry, where both model and mimic must live in the same place (there are a few exceptions: see quiz question at bottom).
Here’s a new tw**t by naturalist and photographer Piotr Naskrecki showing three beautiful Müllerian mimics: members of the Ampulicidae (tropical “cockroach wasps”), Apidae (various kinds of bees), and Chrysididae (“cuckoo wasps”). All are dangerous to predators (they sting), and all have similar, obvious metallic-green coloration. This can be considered a mimicry ring, and I suspect they all share at least one potential predator (probably a bird).
Müllerian mimics are usually quite pretty but these families of stinging insects take it to the next level. pic.twitter.com/JAar9xlN3K
— Piotr Naskrecki (@naskrecki) January 29, 2017
Here’s Quiz Question #2: there are a few cases of Batesian mimicry in which the model and mimic live in different places. How do you suppose that could happen?
h/t: Matthew Cobb, inveterate Twitter-scanner
If the predator lives in both?
I was thinking that perhaps the two species’ ranges overlapped in the past but climate/habitat changes lead to the localized extinctions.
Similarly, that the predator migrates between habitats of the mimic and their model.
That’s my guess.
My guess too
Mine too.
Really cool. I had not considered metallic green to be a warning color, but one must bear in mind that the predator may not see them the way we do.
First Answer:
I hypothesize that two species could share some phenotypes and double their chances of not getting eaten.
Second answer:
I bet in the case of migrating birds who cover much ground, it could be advantagious to look like another poison that they eat in a different area. So if predator A travels from Canada to Mexico and eats a poisonous orange insect in canada and associates that colour and pattern with poison, if a mutant mimic forms in mexico, that same bird will avoid it.
I’ll elaborate the first answer by saying that if the two prey species are unequal in number, then a member of the less numerous species can gain an advantage by switching team colors to those of the more numerous (since more predators will have learned an aversion to that species).
If the two prey species are roughly equal in number, then either can gain an advantage by shifting to an intermediate form that triggers the aversion of predators who learned on either species.
Good point. To add one more thing, id say the larger the group of poisonous creatures with similar traits, the more opportunity for the preditor to eat one and learn. As long as the preditor recognizes them as being one group, both groups gain from their group becoming larger. Is that why we see spiders with hourglass patterns?
doubles their chance of not being eaten, but perhaps also cuts down the amount of time predators need for learning; two different-looking species means the predator has to learn to avoid both by eating both, but if one species begins to look like the other, then the predator need only eat one to learn to avoid both, basically, I think it’s a lower mortality rate for the mutant.
Great pic!
Third paragraph: Bates’ name is inverted. Should be Henry Walter Bates.
For a second there I though you were calling Matthew Cobb and invertrebrate.
I have gone into snowflake mode. Fritz (Johann Friedrich Theodor) Müller (1822-1897) was naturalized Brazilian on Aug. 9, 1856, a few years before he or anyone knew what Darwin was up to, and is probably best referred as Brazilian German, or just Brazilian. He was a “48er” — Fritz participated actively in the failed democratic uprisings against the European aristocracy in 1848 — and immigrated to Brazil in 1852 because he figured he was marked for life in Europe. Müller was also a free-thinker. In 1844 he received a doctorate in biology in Berlin and in 1849 completed a course in medicine. However, he refused to take the Christian oath upon graduation and for this was denied both diploma and the right to practice medicine. After arriving in Brazil, he never returned to Europe. Germany gave up any right to his accomplishments and, had he won a Nobel Prize, it would have been chalked up to Brazil. Fritz Muller’s birthday is March 31. He was the father of 11 daughters.
Wasn’t Marx part of the 1848 diaspora too? Or am I thinking of someone else?
Yes, Marx cast up in London. Another prominent biologist among the 48ers was Richard Schomburgk, who went to Australia.
Fascinating stuff. Are there cases of coexisting Batesian *and* Mullerian mimicry? That is two unpalatable species are similar and then a third, palatable species is similar to the Mullerian mimics.
Yes, these exist.
Eleven daughters? No sons? Sounds like meiotic drive!
My guesses for both questions have been elaborated by others already. It was interesting to think about them. I’m interested now to see whether the suggested answers are correct!
Something else which I find interesting is that the suggested answers are logical solutions based on the premises of chance mutation and natural selection, whether they are the correct answers or not. Without those principles it would be very difficult to come up with any answer at all. What is extraordinary about creationists is that they have zero interest in making logical sense of biological facts; their minds being completely satisfied with a one size fits all explanation: God did it.
Quiz 1: It may free the mimic from having to produce its own toxic chemical, which is metabolically costly, and get a free ride by resembling the other species.
Quiz 2: If the predator lives in a larger area that includes both species range.
Today I learned
Apo=away
Sematic=Sign
Question #2: After Noah’s flood, the population got separated as the waters subsided 😉
Will there be official answers to the quiz questions? I have been scratching my head all day.
Question 1 –
If a member of species A looks slightly more like species B than its fellow-members then it retains all the advantages that come from having A-avoiding-predators steer clear of it (the apple will not fall that far away from the tree that it would lose the benefits of its species-phenotype) and a slight advantage with respect to B-avoiders. The same would be true for members of B with a slight resemblance to A. This slight resemblance would be inherited preferentially and over evolutionary time the two species would slowly evolve towards each other in appearance in a manner similar to Batesian mimicry. They would presumably ‘meet’ in the middle at a point likely to be closer to whichever is the larger population.
That’s my guess, anyway.
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What he said
It is easy to see how Batesian mimicry might evolve given that there already is another poisonous species to imitate. The evolution of the warning signals in the first place is more puzzling. Must the first mutant acquire its poison and its colors at the same time, or does the coloring evolve in already dangerous species? Either way, you would think that the first mutant with bright colors would derive no benefit.
Are there any good models that show how it might develop?
A possible mechanism, based on one suggested by R.A. Fisher in 1930, follows: Starting with a noxious but cryptic prey species, although some predators may learn to recognize it, others, even after unpleasant experiences, might continue to confuse it with unmemorable good-tasting prey and attack it and kill or injure individuals. Individuals of the ‘protected’ prey that vary by having slightly exaggerated distinctive markings (e.g., a small yellow or red spot that is slightly enlarged) that make them more different from the run-of-the-mill camouflaged prey will tend to be confused less and learned quicker, and therefore on average may be more immune to attack after they are seen than their more cryptic cousins. Step by step, the ‘poisonous’ prey should be selected to become more distinct and easier to recognize — i.e., warningly colored — before an attack is initiated and recognized when farther away.
Seems to me that kin selection could also play a role. Eat me, and learn to regret it, and leave my siblings and children alone.
Question 1: Not all predator species find them unpalatable and appearing like the other provides further protection
Question 2: Overlapping predator ranges and convergent evolution but without the development of the nasties just the physical characteristics
“…and this means that that predator has to have had at least one experience with the model to induce learning”
Is it necessarily the case that aposematism and associated batesian and mullerian mimicry pairs or rings must involve predators learning that the warning colouration is associated with a noxious taste (or other unpleasant experience?).
A genetically programmed disposition to avoid certain colour combinations (e.g yellow and black)might confer and advantage and would not require naive individuals to go through the unpleasant (and with some aposematically marked animals, potentially fatal)experience of learning why it is wise to avoid that type of marking. To get started this could work in a similar way to the evolution through sexual selection of bizarre ornamentation where an arbitrary initial preference of one gender for a particular feature in potential mates becomes self reinforcing but in this case it is an arbitrary dislike of a feature in a potential prey item.
It is also possible that a predator that normally has to learn to avoid aposematically marked (potential) prey could in time evolve an inherent avoidance of them if a chance mutation giving rise to a tendency to avoid certain colours occurred.
I guess that inherent avoidance of aposematic prey items can be tested for quite easily in a laboratory using naive individual and probably has been – can anyone advise on this?
Quiz:
1/ one became extinct where it lived with the other species
2/ the mimicry no longer had value so became independent of an association
3/ the mimicry was of some feature that is protective like the yellow/black of many wasps, that is generally protective, so having been selected to imitate, the imitator can spread elsewhere & does not rely on the other species…
???
#1 Even if looking like another species had extra benefits for avoiding predation, wouldn’t these need to be very substantial in order to offset the likely decrease in ability to find a mate caused by looking like another species?
#2 Migratory predators and extinction in the overlapping areas of their ranges both sound possible.
I’m guessing that most insects don’t recognize potential mates by sight, but rather by sound or smell.
Will we ever know the correct answers to the quiz? 😛