Adventures Among Ants - Mark W. Moffett [193]
23. This overlap in generations is shared by ant colonies and the cells of most organisms (see Conclusion). No wonder some scholars think our idea of an integrated, coherent self is something of an illusion. See, e.g., Daniel M. Wegner, The Illusion of Conscious Will (Cambridge, MA: MIT Press, 2003).
24. In most other ants that reproduce by fission or budding, a new nest develops a separate identity from its parent (see chapter 4, n. 18). The supercolonies of the Argentine ant (and likely some other invasive ant species) more closely resemble the individuals of some fungi that spread through soil for centuries, with one Oregon mat covering 10 square kilometers; see ML Smith, JN Bruhn, JB Anderson 1992, The fungus Armillaria bulbosa is among the largest and oldest living organisms, Nature 356: 428–431.
25. Linda Stone, Paul F. Lurquin, and Luigi Luca Cavalli-Sforza, Genes, Culture, and Human Evolution (New York: Wiley-Blackwell, 2007).
26. Species are expected to be genetically distinct, and in fact each Argentine ant supercolony has been found to have a different hydrocarbon “fingerprint”—a combination of the surface chemicals likely to be genetically determined and essential to colony (and in this case species) identity; see CW Torres, M Brandt, ND Tsutsui 2007, The role of cuticular hydrocarbons as chemical cues for nestmate recognition in the invasive Argentine ant (Linepithema humile), Insectes Soc. 54: 363–373.
27. I cite the biological species concept as defined in Ernst Mayr, Principles of Systematic Zoology (New York: McGraw Hill, 1969), p. 26. As discussed on p. 133, isolation doesn’t require a mountain range: insect populations can become isolated even within a single crown of widely separated tropical trees—the space between crowns being in effect mountain ranges in miniature. Other modes of speciation can be important as well; see, e.g., Douglas J. Futuyma, Evolution (New York: Sinauer, 2005), pp. 353–404. In practice, admittedly, Mayr himself had a double standard in distinguishing species; see M Schilthuizen 2000, Dualism and conflicts in understanding speciation, Bioessays 22: 1134–1141.
28. This may generally be how distinct colonies originate in the Argentine ant, though it’s possible that mating flights, thus far undetected in Argentina and abroad, occur on rare occasions. My hypothesis does not require any changes (in particular, convergent changes) in Argentine ants each time they are introduced abroad. Discussions of this ant have been muddied by confusion about what a colony is in this species; it is definitely not a single nest, as is often implied (see, e.g., PT Starks 2003, Selection for uniformity: Xenophobia and invasion success, Trends Ecol. Evol. 18: 159–162). Contrary to what Starks writes, Argentine ants never exhibit “indiscriminate altruism” or a “breakdown in normal nestmate discrimination behavior.”
29. Early human hunter-gatherer bands were small but relatively open and fluid because of the need for exchanging mates between groups, which meant many groups shared family ties. Our identification with fixed groups developed later, after agriculture gave rise to larger, sedentary communities that were kept together by leaders demanding tributes and allegiance. Among other mammals, herds are the largest groups, but these do not have delimited memberships and are not considered societies. Their members not only do not cooperate, e.g., in rearing young, but also exercise strong self-interest, e.g., in avoiding predators.
30. The range expansion of the Argentine ant supercolonies is likely to continue: see N Roura-Pascual, AV Suarez, C Gómez, P Pons, Y Touyama, AL Wild, AT Peterson 2004, Geographical potential of Argentine ants (Linepithema humile) in the face of global climate change, Proc. R. Soc. Lond. Ser. B 271: 2527–2534.
31. In addition to the red imported fire ant, Solenopsis invicta, discussed here, the southern United States has another destructive but less widespread