Nabokov was right all along

January 27, 2011 • 7:31 am

This is a really cool result: a paper published 66 years ago, speculating about the evolutionary history of a group of butterflies, has just been vindicated by a combination of new molecular and ecological work.

But what is even cooler is that the author of the earlier paper was Vladimir Nabokov.

You know Nabokov (1899-1977) as a famous writer, author of, among other books, Lolita, Pnin, Pale Fire, and Speak, Memory.  He also taught literature at Cornell from 1948 to 1959; his classroom lectures have been published and they are absolutely superb.

But what you probably didn’t know was that he was also a world-class lepidopterist, specializing in the “alpha taxonomy” (description and publication of new species) of butterflies.  From 1945-1948 he was Curator of Lepidoptera at Harvard’s Museum of Comparative Zoology (MCZ), the institution where I got my Ph.D.  If you read his novels, you’ll often find a mention of butterflies.

Here’s Nabokov at the MCZ in 1945, from the article on his butterfly work at the New York Public Library Site:

Nabokov’s speciality was the butterfly subfamily Polyommatinae (called “blues” because of their color) in the family Lycaenidae.

Lycaeides melissa, subspecies samuelis. A “bluefrom the northeast U.S.  The species was first described by Nabokov.

In 1945 Nabokov published a formal description and revision of some lycaenid butterfies in Psyche, the journal of the Cambridge Entomological Club (I’m a member!).  Here’s the title of his paper:

The paper is long (62 pages), and largely devoted to describing species based on their genitalia, the character that seems to evolve most rapidly among insects—and many other groups, probably because of sexual selection (see William Eberhard’s excellent Sexual Selection and Animal Genitalia).  At the end of the paper he speculates, based on the morphology of the various species, that the “blues” arrived in the New World from Asia over the Bering Strait.  He further speculated that there were actually five successive invasions from Asia, each giving rise to a different New World group.  And the first invasion produced species that made it to Central and South America, with the North American representatives eventually becoming extinct.

A group of investigators from a bunch of places, led by my friend Naomi Pierce at Harvard, just tested Nabokov’s theory with the modern tools of molecular biology and systematics.  Their results, published in a paper in the Proceedings of the Royal Society (free access!) and described by Carl Zimmer in yesterday’s New York Times, show that Nabokov was right on all counts.

Here’s what the authors found:

  • Using six genes, they made a molecular phylogeny of 73 species of blues from all five “sections” described by Nabokov.  This analysis showed that, indeed, the five separate invasions posited by Nabokov each produced a monophyletic group (i.e., a group descended from a single ancestral species). The butterflies also descended, as Nabokov posited, from Asian ancestors, and certainly came to the New World by migration over the Bering Strait.
  • The oldest group was, as Nabokov suggested, the butterflies in the neotropics: Central and South America.  The other groups were younger, and in the precise age sequence that Nabokov posited had arrived from Asia (and then radiated in North America).
  • The branches of the phylogeny were dated using a “molecular clock.” They were found to have begun about 11 million years ago, and continued until about 1 million years ago.  During the earliest part of that period the Bering Strait was not continuous between Asia and North America, and so some of the ancestral blues must have crossed an expanse of ocean.
  • The authors then determined the temperature-tolerance ranges of each group based on the climate where its members are now living.  From that, they reconstructed the temperature tolerance of each group’s ancestors. (You can do this for any measurable trait, morphological or physiological, using a method called “ancestral character state reconstruction”.)  And they found that the temperatures tolerated by each successive invader declined over time.  The earliest invader tolerated higher temperatures than the next, and so on for all five invasions.
  • The spiffy result: the temperature tolerances posited for each ancestor matched very nicely the temperatures thought to have prevailed in “Beringia” (the region on either side of the Bering Strait) at the time of the invasions.  Here’s part of the authors’ Figure 1, showing the temperature tolerances of ancestors during each of the five invasions (vertical bars), and the temperatures posited to have existed in Beringia, all over the 11 million years from the first to the last invasion:

Note the good match between the actual temperatures in Beringia and the temperatures tolerated by the ancestral invader of each of the five groups. Clearly, the butterflies now in the neotropics tolerated high but not low temperatures, and so were likely driven to the south as the climate became colder.  This also implies that each group has pretty much retained the ancestral temperature tolerance of its ancestor, though the ancestral five groups did diverge from one another in tolerance.

What a lovely piece of work, and how nice that the modern work, using all the highfalutin tools of molecular biology, systematics, ancestral state reconstruction, and so on, managed to confirm the speculations of one itinerant zoologist/author equipped only with a microscope and a bunch of butterfly genitals!

h/t: Carl Zimmer for providing pdfs.


R. Vila, C. D. Bell, R. Macniven, B. Goldman-Huertas, R. H. Ree, C. R. Marshall, Z. Bálint, K. Johnson, D. Benyamini, and N. E. Pierce.  2011.  Phylogeny and palaeoecology of Polyommatus blue butterflies show Beringia was a climate-regulated gateway to the New WorldProc. R. Soc. B published online before print January 26, 2011, doi:10.1098/rspb.2010.2213

25 thoughts on “Nabokov was right all along

  1. …wait, that can’t be right…there was only one Ark, right? Shouldn’t they all have migrated at once after the flood?


    Nice work.

    1. Have you ever noticed how the Ark story never mentions soil bacteria, slime moulds, fungi, – plants for goodness sake… fish (fresh water)… 😉

  2. It’s almost like there are multiple lines of evidence converging to show that evolutionary theory is an accurate description of how life developed.

    1. No. These are trials of god, testing the strength of your faith.
      (Really, logic can hardly get any more twisted.)

  3. Fascinating!

    Do the temperature tolerances relate to the food types that the caterpillars & adults feed on? The ancestral species may have used a hardier food source I suppose?

    1. I took them to be metabolic limits. Outside of those limits, the butterfly dies of hyper- or hypothermia.

  4. I’m a little bit worried that we are seeing what we want to see in the graph. Obviously, I am no expert on these matters, so I would really like some convincing. To my eye the butterfly data would just as well fit a horizontal temperature line positioned somewhere near 0 degrees.

    1. The point is that the mean annual temperature at Beringia was in each case comfortably above the low-temperature limit for each population. A mean temperature of zero degrees 11 million years ago would have precluded population 1 from making the crossing.

  5. VN is genius. A great thinker across many realms. His novel Pnin inspired me to do a whole slew of reading on the tragicomic realm of “academic fiction”. I started with Pnin, then onto “Lucky Jim” then onto the seemingly overlooked “Pictures from an Institution” then onto many David Lodge novels. Funny stuff.

    1. It just goes to show that the distinction some make between “artsy-fartsy” great thinking and “scientific” great thinking really shouldn’t be made. Great thinking is great thinking, period. The greatest artists, musicians and poets don’t stab about in the dark, with only their “emotions” to guide them, and no real idea what they’re actually doing, in a more scientific sense.

  6. “one itinerant zoologist/author equipped only with a microscope and a bunch of butterfly genitals!”

    This man needed medical attention….

    But seriously, one of the most remarkable things about Nabokov was the fact that English was only his 3rd or 4th language (if memory serves) and yet he was regarded as a superb stylist… and, he learned the language late, insofar as language learning goes, having been displaced from Russia as a young man by the Revolution (memory is speaking here, but it tends to mumble these days). He wrote somewhere–probably in Speak, Memory–about missing the wonderful cadences and rhythms of the Russian language.

    On his western collecting trips, Nabokov sometimes stopped by the entomology museum at UC Berkeley to donate butterfly specimens–on the condition that any new species be named after him. (This according to my friend, Constantine Slobodchikoff, who did his PhD there.) (Presumably the donations were not lyceanids; otherwise he would probably have done the naming deed himself.)

  7. I always wonder which of the boys – Shem, Ham or Japhet – went up to the Arctic for the polar bears, which
    one went down to Australia for the kangaroos and which one stayed home to clean the cages. Whoever the last one was, he was the smart one, when you start imagining what the other two had to accomplish.

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