Vladimir Nabokov

NABOKV-L post 0005480, Tue, 19 Sep 2000 21:04:59 -0700

Nabokov and Mimicry (fwd)
From: Arthur Glass <goliard@worldnet.att.net>

The whole idea of 'perfection' sounds very Plaronic to me. Or is perfection
defined as a mimic strategy that is 100% successful?

> From: Kurt Johnson <belina@dellnet.com>
> For sometime now, a lingering question among Nabophiles (both on
> Nabokov-on-line and at the NYTimes.com Nabokov Forum) has been "what does
> modern genetics say about how exact the mimic in mimicry can become? does
> a scientific explanation account for this? and what of Nabokov's noting
> that perhaps some mimicry in nature was so exact as to defy a mechanistic
> explanation? Current genetics' "take" on this has been one of the loose
> ends in Nabokov's Blues and Nabokov's Butterflies discussions. The
> matter also came up in my last personal discussion with the moderator of
> this forum, D. Barton Johnson.
> I decided to ask the question to a Nabokov-literate geneticist. This
> answer is from Dr. James Mallet, a professor at the University of
> London. Jim is not only an expert in mimicry genetics (specializing in
> mimicry in Heliconian butterflies ["Longwings"]) but recently reviewed
> Nabokov's Butterflies in the prestigious scientific journal
> NATURE. Here is his answer to the above questions.
> Dear Kurt,
> Well, I am not so much of an expert on Nabokov, but I suppose I might be
> classed as an expert on mimicry genetics.
> 1) From the 1960s onwards, an enormous literature on the evolution and
> genetics of mimicry has appeared. The major conclusion of evolutionary
> biologists is: yes, natural selection can and does explain the evolution
> mimicry. Nobody today seriously disagrees, and my own view certainly
> conforms with this.
> a) To my knowledge, no mimicry gene has yet been sequenced and
> characterised at the DNA level (work is ongoing at the moment), but
> Nijhout's book as well as many other publications provide evidence that
> normal genetic mechanisms are at work to produce mimetic adaptations.
> b) Natural selection on mimicry of warningly coloured butterflies has been
> studied in the field, and it has been shown that predator selection
> pressures can be very intense. I did one such experiment myself: the
> butterflies with the wrong colour pattern had half the lifespan of the
> butterflies with the mimetic pattern. This provides a powerful force of
> natural selection for mimicry!
> c) Of course, experiments like these are usually done on extremely
> different mimics and non-mimics (otherwise, the effect would be weak, and
> experiments would require impossibly huge sample sizes). The experiments
> therefore do not specifically answer the question about perfection.
> Obviously, perfect mimicry is likely to be only a little advantageous over
> fairly good mimicry. Very likely we wouldn't be able to measure the
> of mimetic perfection in experiments with even a few hundred predators and
> prey. But given that major changes have very major fitness effects, it
> seems almost certain that very slight improvements will have small fitness
> advantages that have appreciable effects over many thousands, and often
> millions of generations. We also know now that many birds and other
> predators have extremely acute vision, often more acute than our own.
> d) Most of the studies have been done in palatable mimics of unpalatable
> butterflies. I read somewhere that Nabokov believed that some spots on
> lycaenid butterflies ("blues") mimicked drops of dew, and that the
> perfection of shading of a 2-D wing spot mimicking the 3-D drop was what
> triggered Nabokov's lack of belief in the power of natural selection. I
> don't know the specific spots to which Nabokov was referring, but I do
> plenty of examples of 3-D eyespots on insects which are made to look like
> real eyes using delicate shading. Given that colour patterns can and do
> evolve, and that eyespots can be very frightening, I can well believe that
> this kind of camouflage would evolve under natural selection. No work has
> specifically been done on the perfection of eyespots, to my knowledge, but
> eyespots and artificial models of eyespots have been shown to be very
> terrifying to bird predators.
> 2) Something that one should always remember is that much mimicry is
> not very perfect at all, in many cases! For example, red and yellow spots
> on the thorax and abdomens of poisonous pharmacophagous swallowtails in SE
> Asia are mimicked by red patches at the base of the wings of their mimics,
> the female forms of the swallowtail Papilio memnon. Another example is
> flies mimicking wasps. Many stinging wasps fold the anterior part of
> forewings, making them look darker at the front edge. Syrphids and other
> flies usually mimic this by means of darker pigment on the front margin of
> the wing, rather than actually folding the wing. This LACK of perfection
> of mimicry, a kind of impressionism, is exactly what one would expect if
> the mimicry were cobbled together by natural selection, rather than
> by a perfect designer.
> I am reminded of a PhD student who was a creationist in this Department.
> He told me he believed that mimicry was too perfect to be explained by
> natural selection. Although he understood and believed in natural
> selection, he really felt this might be evidence for the guiding hand of
> the creator. He suffered a nervous breakdown, and has never completed his
> PhD. Possibly the stresses that had built up between his excellent
> knowledge of evolutionary biology and his faith played a role in making
> life difficult for him. Perhaps Nabokov, who produced his "mimicry too
> perfect" argument as far back as in "The Gift", was perhaps not thinking
> too carefully about the data when he made these claims. Maybe it is just
> as well for his sanity that Nabokov never did write that book on mimicry
> which he discussed with a publisher!
> This is probably too long for you, but oh well!
> Jim
> Prof. James Mallet