Digging beneath the surface: incipient nest characteristics across three species of harvester ant that differ in colony founding strategy

Abstract

Ants exhibit a size-associated colony founding trait that is characterized by the degree to which foundresses rely on internal reserves to raise their first brood of workers (claustrality). The reliance on stored reserves is positively correlated with degree of claustrality (claustral [ facultative [ semi-claustral) and is variable across species of Pogonomyrmex harvester ants. Three species of harvester ant foundresses that differ in degree of claustrality were observed initiating nests under laboratory conditions over 2 years. P. rugosus is fully claustral, P. salinus is facultative, and P. californicus is semi-claustral. Across species, degree of claustrality was positively associated with mean digging rate and nest depth over the first 3 days of nest initiation, total nest depth, and degree of nest closure. Branching and abundance of peripheral nodes were higher in semi-claustral and facultative nests than in claustral nests. The facultative species dug for the longest time and achieved the greatest tunnel length. Within each species, there were trends associating mass with digging rate, but these were not consistent in all species. There were no intraspecific trends of mass with nest depth. Also within species, a foundress's mass did not affect her tendency to open or close her nest. These results reveal degree of claustrality is correlated across species with several nest initiation characteristics that together may represent different colony founding syndromes.

Foraging for the fungus: why do Acromyrmex subterraneus (Formicidae) queens need to forage during the nest foundation phase?

“…We suggest that as Spoiled queens did not leave the chamber, they could have had more time to dedicate towards the rearing of larvae, pupae, and fungus. Foraging trips of Acromyrmex octospinosus queens can take up to 182 min (Fernández-Marín et al, 2003), a considerable amount of time, which could instead be put towards raising brood (Enzmann & Nonacs, 2010). In semiclaustral species, the energy and time spent foraging may also restrict brood care, as already verified for nest construction (Enzmann & Nonacs, 2010).…”

“…Foraging trips of Acromyrmex octospinosus queens can take up to 182 min (Fernández-Marín et al, 2003), a considerable amount of time, which could instead be put towards raising brood (Enzmann & Nonacs, 2010). In semiclaustral species, the energy and time spent foraging may also restrict brood care, as already verified for nest construction (Enzmann & Nonacs, 2010). For Spoiled queens, this time could also be invested in hygienic behaviours which improve larvae and fungus development (Fernández-Marín et al, 2003;Augustin et al, 2011).…”

The emergence of reproductive division of labor in forced queen groups of the ant Pogonomyrmex barbatus

“…Reproduction was also unrelated to excavation role, indicating that the emergence of reproductive division of labor was inherent to this task rather than resulting from a trade-off in investment among potential tasks (Jeanson et al, 2007). This differs from the congener P. californicus, in which the two tasks are negatively related (Jeanson & Fewell, 2008); a key difference may be that P. californicus nests in loose, sandy soil and does not seal the nest entrance (Johnson, 2004;Enzmann & Nonacs, 2010), extending the duration of this task well into the egg-laying period and creating an excavation-reproduction tradeoff in individual time budgets. This tradeoff is further exacerbated in P. californicus by the fact that queens actively forage for resources, limiting the time available for other tasks and physically separating the forager from the nest and brood (Johnson, 2002;Dolezal et al, 2009). One striking difference between the two tasks is the effect of queen pairing on total task performance.…”

Systematics of harvester ants (Messor) in Israel based on integrated morphological, genetic, and ecological data

“…The influence of abiotic factors such as soil properties and topography on distribution, survival, and establishment has been reported in congeneric Messor barbarus Linnaeus 1767 colonies (Baraibar et al 2011;Enzmann & Nonacs 2010;Johnson 1998;Wiernasz & Cole 1995, Crist & Wiens 1996. Toughness, texture, and moisture of the topsoil affected the ants' ability to excavate and build nest chambers (Boulton et al 2005;Enzmann & Nonacs 2010;Johnson 1998;Wiernasz & Cole 1995).…”