title: Excavated substrate modulates growth instability during nest building in ants.
abstract: In social insects, the nests of the same species can show a large difference in size and shape. Despite these large variations, the nests share the same substructures, some appearing during nest growth. In ants, the interplay between nest size and digging activity leads to two successive morphological transitions from circular to branched shapes (budding along the perimeter of the circular cavity and tunnelling of the galleries). Like several other self-organized collective behaviours, this phenomenon, as well as the entire nest-digging process, is thought to be modulated by environmental properties. The present study investigates the effect of excavated substrate on the nest morphogenesis and the morphological transitions by using two materials with different cohesions. Here, we show that the two morphological transitions occur more frequently with a cohesive substrate than with a granular one: 96 per cent of cohesive experiments showed both transitions, whereas only 50 per cent did in granular experiments. We found that transitions and excavation cessation follow area-response thresholds: the shape transitions take place and the digging activity stops when the dug area reaches the corresponding threshold values. The shape transition thresholds are lower with the cohesive substrate and that of stopping digging is independent of nest shape and material. According to simulations, the experimental frequencies of transitions found their origin in the competition between transitions and activity cessation and in the difference between the transition threshold values of each substrate. Our results demonstrate how the substrate properties modulate the collective response and lead to various patterns. Considering the non-specific mechanisms at work, such effects of substrate coarseness have their counterparts in various collective behaviours, generating alternative patterns to colonize and exploit the environment.
authors.affiliation: Service d'Ecologie Sociale, CP231, Université libre de Bruxelles, Plaine Campus, Boulevard du Triomphe, 1050 Bruxelles, Belgium. etoffin@ulb.ac.be
authors.forename: Etienne
authors.initials: E
authors.lastname: Toffin
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kindekens
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Deneubourg
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D000818:Animals; D001000:Ants / Q000502:physiology*; D000077215:Clay; D004777:Environment; D009425:Nesting Behavior; D012822:Silicon Dioxide / Q000737:chemistry; D013046:Specific Gravity; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D012822:Silicon Dioxide; D000077215:Clay
references.citation: Oecologia. 2008 Nov;158(1):165-75
references.pmid: 18668265
references.citation: Trends Ecol Evol. 1997 May;12(5):188-93
references.pmid: 21238030
references.citation: J Insect Physiol. 2007 Nov;53(11):1160-8
references.pmid: 17689556
references.citation: Philos Trans A Math Phys Eng Sci. 2003 Jun 15;361(1807):1263-82
references.pmid: 12816611
references.citation: Anim Behav. 2000 May;59(5):1061-1069
references.pmid: 10860533
references.citation: J Insect Sci. 2005;5:9
references.pmid: 16299599
references.citation: J Insect Physiol. 2004 Jul;50(7):629-35
references.pmid: 15234623
references.citation: J Insect Sci. 2004;4:21
references.pmid: 15861237
references.citation: Anim Behav. 1997 Oct;54(4):779-96
references.pmid: 9344432
references.citation: Science. 1995 Aug 4;269(5224):686-8
references.pmid: 17758813
references.citation: Philos Trans R Soc Lond B Biol Sci. 2006 Jan 29;361(1465):5-22
references.pmid: 16553306
references.citation: J Insect Sci. 2002;2:3
references.pmid: 15455037
references.citation: J R Soc Interface. 2007 Feb 22;4(12):107-16
references.pmid: 17015288
references.citation: J Insect Physiol. 2008 Mar;54(3):534-42
references.pmid: 18221944
references.citation: Naturwissenschaften. 2001 Jul;88(7):301-5
references.pmid: 11544898
references.citation: J Theor Biol. 1999 Jun 21;198(4):575-92
references.pmid: 10373356
references.citation: Proc Natl Acad Sci U S A. 2009 Nov 3;106(44):18616-20
references.pmid: 19846774
references.citation: Biol Bull. 2002 Jun;202(3):268-74
references.pmid: 12086999
references.citation: Naturwissenschaften. 2004 Dec;91(12):602-6
references.pmid: 15517133