Supercolonies

Sorger et al. (2016) - Certain ants form complex societies that allow them to achieve ecosystem dominance (Holldobler and Wilson 1990). The most extreme species form extensive cooperative units called supercolonies with the capacity to expand their nest sites over large areas, in some cases thousands of square kilometers, yet maintain a clear separation from other [super]colonies. Supercolonies are almost exclusive to ants (but see Leniaud et al. 2009). As in ants generally (Holldobler and Wilson 1990; Tsutsui 2004), these polydomous ants identify their colony by specific cuticular hydrocarbon profiles. This identification is retained following budding (Torres et al. 2007) such that individuals may move freely among nests where the environment permits, intermixing and thereafter cooperating indiscriminately with any other portion of that colony [in some instances low-level aggression may occur, at least temporarily (Roulston et al. 2003)]. Furthermore, in species like the Argentine ant (Linepithema humile), colony growth seems to continue as long as suitable unoccupied space is available (Buczkowski and Bennett 2008; Van Wilgenburg et al. 2010). Therefore, a colony can take over huge expanses but nevertheless have a clear membership and distinct boundaries (Torres et al. 2007). The capacity of a colony to extend its range without constraints is the strongest basis for describing such ants as having supercolonies (Moffett 2012). Supercolonial ants have multiple queens (they are polygynous), which permit their exponential growth rate and spatial expansion to occur not only through budding, but also through jump-dispersal potentially over long distances. Because of their nesting and dietary generalism, invasive ants with supercolonies are especially successful as stowaways in human cargo (Holway et al. 2002). Over the past century, jump-dispersal has expanded the natural range of numerous species of invertebrate (e.g., Ascunce et al. 2011; Booth et al. 2011; Saenz et al. 2012; Gotzek et al. 2012) and in the ants has led to the very same supercolonies ranging between continents (Vogel et al. 2009; Sunamura et al. 2009; Vogel et al. 2010).