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Posts Tagged ‘superorganism’

Figure 1. Relationship between normalized metabolic rate and body mass for unitary organisms and whole colonies (from Hou et al 2010)

The notion that insect colonies and their constituent individuals are analogous to multicellular organisms and their constituent cells has been a controversial idea for decades. Is it useful, for example, to think of an ant colony as a single individual? Do superorganisms really exist as coherent entities? Or do insect colonies function more as aggregations of individuals?

Last week, PNAS published the first application of empirical methods to test the superorganism concept. This is a significant paper. The researchers, led by Chen Hou, asked whether the set of relationships between mass, energy, and reproduction that govern multicellular organisms show the same patterns when measured across whole insect colonies.

The answer, in most cases, was a resounding Yes: social insect colonies grow and breathe just like regular organisms.

source: Hou, C., Kaspari, M., Vander Zanden, H. B., Gillooly, J. F. 2010. Energetic basic of colonial living in social insects. PNAS early edition.

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Sorry to keep harping on Hoelldobler & Wilson’s The Superorganism.  But Wilson’s section on ant evolution is so bad, so out of touch with the state of the field that I can’t help but to rant.

Both Chapter 7 (The Rise of the Ants) and Chapter 8 (Ponerine Ants: The Great Radiation) are predicated on the argument that certain groups of poneromorph ants form a clade. In defense of this assumption, Wilson writes (page 322):

…Barry Bolton has recently split Ponerinae into seven subfamilies (Ponerinae, Amblyponinae, Ectatomminae, Heteroponerinae, Paraponerinae, Proceratiinae, and the fossil Brownimyrmicinae).  Still, there is no reason as yet to doubt that the assemblage as a whole represents a diversification from a single Mesozoic ancestor.

No reason, that is, except that it runs contrary to the findings of every single relevant phylogenetic study* in the past decade.  In particular, there is simply no way to make (Ectatomminae + Heteroponerinae) monophyletic with the remaining poneromorphs given the existing data, and even the monophyly of the remaining groups is far from certain.  Wilson stakes his claim even further in the mud on the next page:

This, then,  is the ponerine paradox: a group that is globally successful yet socially primitive.  The puzzle might be partially resolved if the more advanced subfamilies can be shown to be derived from a ponerine stock…but even if such proves to be the case (contrary to the opinion of systematists who consider the ponerines basically monophyletic), there likely remain diverse modern subgroups…

Who are the systematists who consider these poneromorphs to be monophyletic?  None that I’m aware of.  Wilson is the last one left, ossified in the same perspective he had in the 1960s.  What’s even odder is that he reproduces the Moreau et al phylogeny on page 316, and it contradicts nearly all of his phylogenetic statements in the text. Did he read the figures in his own book?

As a consequence, the whole section of The Superorganism devoted to the evolutionary history of ants is muddy, incoherent, and entirely at odds with the increasingly clear picture emerging from modern studies of ant relationships.

*Astruc et al 2004, Moreau et al 2006, Brady et al 2006, Ouellete et al 2006, Rabeling et al 2008.

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wilson1Who is supposed to read The Superorganism?

I can’t really tell.  While I’m enjoying Holldobler & Wilson’s latest tome, I am perplexed at the book’s target audience.  The text switches between broadly anthropomorphic prose clearly aimed for a general audience and obtuse jargon digestible only by the experienced biologist.

I get the feeling that the authors- at least one of them, anyway- desired a technical book more along the lines of Bourke & Franks, while the marketing department at Harvard University Press wished to trade on the authors’ name recognition with a glossy coffee-table production.  The tug-of-war behind the scenes must have been impressive, and the effect is surreal.  It’s a bit like hanging your automobile’s operating manual in a gilded frame over the mantle.  The result is not unpleasant, mind you, but I can’t help to think the authors missed an opportunity to produce either a comprehensive professional review or an engaging popular work instead of compromising in the middle.

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In the comments, Eric Eaton makes an observation:

I’m left wondering (just a little) why Alex has such a beef with Dr. Wilson. This is not the first post taking a jab at Wilson, so while Alex makes an excellent point, I’m also sensing some underlying issues here….

Eric is right there’s an issue.  It is one many myrmecologists, especially systematists, have been tip-toeing around for a while now.

The short version is that Wilson is no longer at the leading edge of myrmecology.  As he has fallen out of step with the practicing research community, his public ant commentary is increasingly at odds with the situation on the ground, as it were.  This predictably puts the current generation of myrmecologists in a bit of an uncomfortable position with respect to the community’s most public representative.  Hence the underlying issues.

The longer version is this.  (more…)

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