Post by Greg Mayer: More thoughts on E.O. Wilson

January 8, 2022 • 1:20 pm

by Greg Mayer

As WEIT readers well know by now, E.O. Wilson died last month at the age of 92. Jerry knew Ed better than I did, but my scientific interests were actually much closer to his than were Jerry’s. I was greatly influenced by Ed and Robert MacArthur‘s theory of island biogeography. The Harvard Gazette just republished an interview with Ed from 2014, and the interviewer asked what he thought his most important contribution was. Ed said there were several, but his work with MacArthur is the first thing he mentioned.

My well-worn copy of MacArthur and Wilson, purchased in 1977, when I was an undergraduate.

I had learned about their ideas–especially the idea that the number of species on an island was the result of a dynamic equilibrium between ongoing colonization and extinction–in my undergraduate classes. I got a copy of their book and began reading it between my sophomore and junior years of college. When I went off to graduate school to work on island lizards with Ernest Williams, I expected that I would wind up applying and exemplifying the principles of the theory.

The title page of my copy, signed by Ed, with an added sketch of an ant; inscribed on 6 October 2007, at the “Island Biogeography at 40” symposium held at the Museum of Comparative Zoology (MCZ). I had brought my copy with me; Ed and I chatted, and he graciously signed it, adding the ant unbidden. The symposium resulted in a book edited by Jon Losos and Bob Ricklefs (reference below).

Ed’s work in island biogeography included theoretical formulation (though the mathematics was primarily MacArthur’s), analysis of faunal lists and distribution patterns, and, very ambitiously, experimental manipulation of species numbers on mangrove islets in Florida. One of his contributions to island biogeography that has gone largely unremarked, but which I regard as of real significance, are his studies of Cenozoic fossil ant faunas in amber from the Dominican Republic. He found that the ancient amber ant fauna was more characteristic of a continental fauna, rather than that of an oceanic island. I was very impressed by this work; at the time it was, and remains to this day, among the strongest evidence that the Greater Antilles are old continental islands– islands once attached to or closely adjacent to the mainland, from which their fauna derives.  (Several of his papers on the amber ants are open access, and are linked below.)

Ed gave a seminar about his amber fossil work while I was a grad student, and we talked afterwards, and he suggested we continue the discussion. Knowing how busy Ed was, I went to make an appointment to see him with his secretary, rather than rely on us passing in the hallway to set a time (Ed was not often in the hallway). His secretary was very suspicious about who I was and what I wanted, and said I would need to write a letter requesting a meeting. The demand seemed to me beyond the pale, considering that I was a grad student in the MCZ and that Ed wanted the meeting. I never wrote the letter, and that conversation never continued.

A few years later, in 1988, James D. ‘Skip’ Lazell and I wrote that the discovery of bolitoglossine salamanders (a mainland group, with little capacity to cross a salt water barrier) in the Dominican amber would be powerful evidence from the vertebrate fossil record for an old continental origin of the Greater Antillean fauna (Wilson’s work having provided invertebrate evidence). In 2015 George Poinar and Dave Wake reported exactly that– a well-preserved bolitoglossine salamander from the Dominican amber!

Many people (including Ed) have commented on Ed’s rather sour relationship with Dick Lewontin. What is sometimes overlooked in these discussions is that both of them were involved with a group known as the “Marlboro Circle”. This group, which sought to conceptually unify ecology and evolutionary biology, included, among others, Ed’s key collaborator, Robert MacArthur, and also Richard Levins. (Levins was a Marxist who made important contributions to island biogeography, collaborated on publications with MacArthur and Lewontin, and visited Wilson’s experimental mangrove islands.)

I find the activities of this group fascinating– in many ways they set the agenda for ecology and evolutionary biology for the second half of the 20th century. It is one of the most important episodes in the biology of that century–that the group was marked by tragedy (MacArthur’s death at 42) and a falling out among its members lends pathos as well. The episode has, unfortunately, been little studied or remarked upon by historians of science. My last communication with Ed (in 2020) was about some of the sources for the data that went into the origination of his and MacArthur’s formulation of their theory.

I mentioned above that I had expected my studies to apply and exemplify the theory of island biogeography, but as I learned more about reptile distribution and did my own studies in the West Indies, I found that species number on islands was not the result of a dynamic equilibrium between ongoing colonization and extinction. Rather medium (10^4 to 10^5 ka, especially ice age changes in sea level) and long term (10^6 to 10^7 ka; the origin and diversification of major lineages) geological and evolutionary events were much more important in shaping the fauna.

Nonetheless, MacArthur and Wilson, like Darwin in the Origin and Mendel in his seminal paper, had limned many pathways for further progress, and despite failing to find evidence of their equilibrium process, I had, and continue to have, the greatest respect for their work. For my thesis defense, I planned to bring two past members of the Marlboro Circle– Dick Lewontin, my advisor, and Ed Wilson, original island biogeographer– back together, at least briefly.

My thesis defense talk was entitled “A theory of island biogeography, with especial reference to the amphibians and reptiles of the West Indies”. (This was a deliberate mashup of the title of Ed’s book and the title of a monograph from 1914 by Thomas Barbour, an early curator of herpetology at the MCZ, “A contribution to the zoogeography of the West Indies, with especial reference to amphibians and reptiles“.) I gave the talk at Dick’s weekly Population Biology Seminar on the 3rd floor of the MCZ Labs, one floor below Ed’s lab.

I tried to make sure that Ed would attend, despite its location, by placing a copy of my seminar announcement in his mailbox. He did come, and sat at the middle of one side of the great table that sat in the middle of Dick’s lab (Dick was further back in the room). I argued in my talk that the equilibrium theory was a special case of a more general theory, and that the equilibrium theory per se didn’t apply very well to West Indian amphibians and reptiles.

After my talk, among the questions were one or two from Ed. He defended the applicability of his and MacArthur’s theory to broader situations than the ones where it fit best, and, indeed, I concur that they had anticipated modifications, expansions, and refinements that would improve it– that’s why I had said there was a more general theory of which theirs could be a special case. After the questions, Ed left.

Although much of Ed’s public reputation rests, rightly, on Ed’s advocacy for biodiversity, and on the controversy over sociobiology (which accounts for essentially all the negative bits), in remembering Wilson we should not lose sight of his other accomplishments.

Losos, J.B. and R.E. Ricklefs, eds. 2010. The Theory of Island Biogeography Revisited. Princeton University Press, Princeton, N.J. publisher

MacArthur, R.H. and E.O. Wilson. 1967. The Theory of Island Biogeography. Princeton University Press, Princeton, New Jersey. publisher

Wilson, E.O. 1985. Ants of the Dominican amber (Hymenoptera: Formicidae). 1. Two new myrmicine genera and an aberrant Pheidole. Psyche 92:1-9. pdf

Wilson, E.O. 1985. Ants of the Dominican amber (Hymenoptera: Formicidae). 2. The first fossil army ants. Psyche 92:11-16. pdf

Wilson, E.O. 1985. Ants of the Dominican amber (Hymenoptera: Formicidae). 3. The subfamily Dolichoderinae. Psyche 92:17-37. pdf

A bizarre case of sound mimicry involving caterpillars and ants

February 7, 2009 • 7:26 am

Mimicry was one of the first pieces of evidence supporting Darwinism, as it wasn’t immediately obvious why a celestial creator would make one creature mimic another, while natural selection could easily explain it if the mimic gained protection or resources by resembling its “model.” The most recent issue of Science–an issue loaded with fascinating studies of evolution–has a really interesting article involving mimicry of sounds.

Ant colonies have been invaded by many species of arthropods who take advantage of the ants’ food stores or presence to gain food or protection from predators. Often natural selection has molded these arthopods to mimic the appearance of the ants. In this issue of Science, however, Francesca Barbero and his colleagues describe a caterpillar that has gone farther–it mimics not only the chemicals of the ants, but also the sounds produced by the ant queen to subdue and gain sustenance from her workers.

Caterpillars of the lycaenid butterfly Maculinea rebeli are carried by one species of ants (Myrmica schencki) into the ant nest, where they are fed by the workers, who normally feed larvae of the ants. Why do the workers feed the alien species? They are deceived by the caterpillar in two ways: the caterpillars mimic the ants both chemically and through sound!

First, the caterpillars secrete chemicals that resemble the chemicals on the surface of ant larvae. Chemical mimicy is not so unusual in insects. What is more remarkable is that both the caterpillars AND PUPAE (the next life stage of the caterpillar) of the butterfly are able to produce sounds similar to those produced by the ant queens (how the caterpillars do this is unknown.) These queens have “stridulatory organs” which they rub to produce special “queeny” sounds that induce the workers to tend and feed them. (The ant workers also make sounds, but they differ form those of the queen). Sure enough, both caterpillar and pupae are able to produce sounds more similar to those of the queen than to those of the workers. Playback experiments of recorded caterpillar and pupal calls demonstrated that these sounds induce tending behavior in the ant workers. This is simply astounding–I am not aware of any other case in which a pupa is able to produce sounds, much less sounds that mimic those of another species. It is this kind of bizarre adaptation, resulting from selection on the butterflies to get free food in the juvenile stages, that gets the juices of evolutionary biologists flowing. The bounty of natural selection is endless: you can never predict what it will come up with.

You can listen to the sounds of the ant queens and workers, and of the larvae and pupae of the butterfly here.

Queen Ants Make Distinctive Sounds That Are Mimicked by a Butterfly Social Parasite.  Francesca Barbero, Jeremy A Thomas, Simona Bonelli, Emilio Balletto, and Karsten Schönrogg, Science 6 February 2009: Vol. 323. no. 5915, pp. 782 – 785