So. I think I will have to start this post by admitting that I haven’t read any Nabokov. I didn’t even know how to pronounce the name until I watched a hockey game wherein one of the goalies had the same last name. So perhaps I have no right to be freaking out as much as I am right now because I didn’t know that Vladimir Nabokov was a frakking butterfly taxonomist when he wasn’t a famous author.
But he was. A reasonably well-respected lepidopterist who didn’t mind injecting a bit of literary flair into his publications (because who reads butterfly taxonomy anyways?). His pet taxon was a section* called Polyommatus. These butterflies are somewhat incongruously called the blues. They are small, and yes, many of them are blue, but many are also brown and have orange and black spots. And they are damn hard to identify, let alone to classify into a taxonomic scheme that reflects their evolutionary history. But Nabokov tried to do this—tried without the help of modern molecular phylogenetic techniques, basically using a combination of morphology, biogeography, and, from what I can tell, intuition to develop a hypothesis for how the Polyommatus clade evolved. Namely, they originated in Asia, crossed to Alaska, and travelled south to the Neotropics, leaving no trace of their sojourn through North America. Then four more waves of colonists arrived to create a North American Polyommatus assemblage. Nabokov even specified the order in which he thought different genera within the section arrived: after the Neotropical group, the ancestor of Icaricia and Plebulina, followed by Lycaeides, Agriades, and Vacciniia. (For fun, Nabokov’s paper on the blues is available here.)
And recently, someone thought to check up on Nabokov’s ideas by comparing them to the evolutionary history of the clade as inferred by genetic data. And, long story short, he was right. For the full story in much nicer prose than mine, read Carl Zimmer’s NY Times piece on the matter.
Not only was Nabokov right that the butterflies came to the New World in waves, he actually got the precise order of colonization right. The ancestor of the Neotropical Polyommatus arrived some 11 million years ago; the most recent arrivals came a million years later. But even if these dates are inaccurate, the order of arrival holds up. (Several different methods converged on more or less the same scenario.) And, fascinatingly, the authors of the new paper present evidence that the ancestral butterflies—the ones who crossed through Beringia—were cold tolerant enough to have lived there at their alleged times of crossing.
The cynic in me had to wonder if it was really that astonishing that Nabokov came to the right conclusion. There are, after, all, few if any good alternative hypotheses. But inferring the order in which the genera colonized—that can’t be a lucky guess. The man knew something no one else did, apparently. And holy frak, I’m moving Lolita to the top of my to-be-read list.
*A sort of vague taxonomic rank, in this case below tribe and above genus. The family to which these butterflies belong was historically a garbage dump where lepidopterists threw species that they couldn’t quite classify anywhere else, and it still hasn’t been properly cleaned up, so there are names attached to putative monophyletic groups that aren’t “proper” families, subfamilies, etc.
Reference: Vila, R. et al. 2011. Phylogeny and palaeoecology of Polyommatus blue butterflies show Beringia was a climate-regulated gateway to the New World. Proc. Roy. Soc. B. doi: 10.1098/rspb.2010.2213