Resource Allocation, Brood Production and Cannibalism during Colony Founding in the Fire Ant , Solenopsis invicta Author(s): Walter R. Tschinkel Source: Behavioral Ecology and Sociobiology, Vol. 33, No. 4 (1993), pp. 209-223 Published by: Springer Stable URL: http://www.jstor.org/stable/4600872 Accessed: 03-11-2015 17:37 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/4600872?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at http://www.jstor.org/page/ info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Springer is collaborating with JSTOR to digitize, preserve and extend access to Behavioral Ecology and Sociobiology. http://www.jstor.org This content downloaded from 128.186.14.5 on Tue, 03 Nov 2015 17:37:58 UTC All use subject to JSTOR Terms and Conditions Behav Ecol Sociobiol (1993) 33:209-223 Behavioral Ecology and Sociobiology ? Springer-Verlag1993 Resourceallocation, brood productionand cannibalismduring colony foundingin the fire ant, Solenopsisinvicta Walter R. Tschinkel Department of Biological Science, Florida State University, Tallahassee,FL 32306-3050,USA Received February 12, 1993/Acceptedafter revision July 3, 1993 Summary.The colony foundingcharacteristics of newly Key words: Pleometrosis - Formicidae - Worker size - mated fire ant queens from monogyne colonies were Cannibalism - Haplometrosis - Colony development. studied in the field and in the laboratoryunder haplo- and pleometroticconditions. Initial queen weight (live) was not correlatedwith subsequentprogeny production. Duringfounding, queens lost a mean of 54% of theirlean Introduction weight, 73% of their fat weight and 67% of their energy content. The percentageof fat decreasedfrom 44% to Ant queensfound new coloniesin one of two ways:either 33%. Queens lost weight or energy in relation to the accompaniedby workers(dependent founding) or unac- amount of progeny they produced(Figs. 1, 2). The effi- companied (independent founding) (Holldobler and ciencyof the conversionof queento progenyincreased as Wilson 1977). Among the majority of independently more progenywere produced,leading to a declinein the foundingspecies, founding is claustral,meaning that the unit cost of progeny (Fig. 3). The more minims a queen queenseals herselfin the foundingchamber and rearsthe produced,the lower the mean weightof theseminims and first brood of workersby drawingon nutrientstores in the fasterthey developed(Fig. 4). In a fieldexperiment on her body (Holldoblerand Wilson 1990). The need for pleometroticfounding, total brood increasedwith queen such largenutrient stores has led to higherlevels of fat in number,peaked betweenfour and seven queens and de- species with claustrallyfounding queens than in those clined with 10 queens (Fig. 5). Brood developedfaster at foundingdependently (Keller and Passera1989). Most of the sunny, warmersite, but total productionand queen this materialis sequesteredbetween adult eclosion and survivalwas higher at the shady site. As queen density the nuptial flight (Kellerand Passera1989). increased,production per queen decreasedas a negative In some claustral ant species, queens may improve exponentialin which the exponent estimatedsensitivity founding success through pleometrosis (co-operative of brood productionto queen-crowdingand the constant colony founding) (Holldobler and Wilson 1977). The estimatedthe productionby solo queens (Fig. 9). These main features of colony founding in Solenopsisinvicta effects of queen number were confirmedin laboratory have been describedby Markinet al. (1972),including the experiments.The decreaseof productionper queen was existenceof pleometrosis.Tschinkel and Howard(1983) small and not always detectable during the egg-laying showed positive relationshipsbetween queen settlement phase, but brood attritionwas always strong duringthe densityand pleometrosis,and betweenpleometrosis and larval period and increasedwith queen number(Figs. 8, foundingsuccess. Pleometrosis may lead to lower queen 10).While airbornefactors may have contributedto this mortality and greaterworker production(Waloff 1957; inhibition,most of the brood reductionwas due to other Bartz and Holldobler 1982; Tschinkel and Howard causes, probably cannibalism.For a given number of 1983).Larger numbers of workersin the firstbrood result minims, increased queen number increased the mean in an advantagein the ensuingcompetition among incip- weight of these minims,an effectthat resultedboth from ient colonies (Bartz and Holldobler 1982; Pollock and a lower minim productionper queen and from cannibal- Rissing 1989;Tschinkel 1992a,b). Central to this compe- ism of dead queens by survivors (Fig. 11). Cannibal tition is brood raiding,the reciprocalstealing of brood queens lost much less weight to producea given number fromneighboring incipient nests by workers(Pollock and of minims than unfed control queens,and these minims Rissing 1989; Tschinkel1992a). Victory usually goes to were heavier(Fig. 12). the nest with more workers,emphasizing the importance of pleometrosisand worker production.Workers soon execute supernumeraryqueens (Tschinkeland Howard This content downloaded from 128.186.14.5 on Tue, 03 Nov 2015 17:37:58 UTC All use subject to JSTOR Terms and Conditions 210 1983),but how they choose the single,surviving queen is tive competition and regulation.Embryonation of eggs unknown. as a regulatorymechanism in foundingcolonies is unex- In most ants, workers produced by the founding plored. queen(s)are distinctlysmaller than any others in the life Althoughthe potentialfor regulationwithin the claus- cycle and are called minims or nanitics (Holldoblerand tral chamberexists, little is known about processesand Wilson 1990).Vander Meer (1986) suggested that minims relationshipsduring this period. In this paper I relate are a behaviorallyand biochemicallydistinct caste. Cer- queenweight, queen number, weight loss, minimnumber, tainly,the role of minimsin brood raidingsuggests some minim size and development rate during the claustral distinctiveminim behavior,but the degreeto which this period,clarifying patterns of the allocation of queen re- is limited to minims is not yet clear (Tschinkel1992a). sourcesunder haplo- and pleometroticconditions. I also The small size of minims may be an adaptivefeature of show that cannibalismof larvaeand queensstretches the fire-antlife history: Porterand Tschinkel(1986) showed resourceswithin the sealedfounding chamber and affects that for a given weight of workers,minims rearedmore allocation patterns. brood than did minor workers of S. invicta.For many species of ants, rapid colony growth is an importantele- ment in survivaland competition(Vargo 1988). Materialsand methods Pollock and Rissing (1989) have pointed out that, whetherpleometrotic or haplometrotic,the sealedfound- Generalmethods. Queens were aspiratedfrom the ground and under ing chamberis a closed system with fixed resources.For litter on the afternoonsof large mating flights in Tallahassee,Flor- the denizens of the founding chamber,the question is ida, USA. All colonies in this area are monogyne. For colony found- how to allocatethese fixedresources in orderbest to meet ing, queens were placed singly or in groups,depending on the exper- the needs of survival,worker production and the post- iment, into one of two types of founding nests. The first consisted of small test tubes half filled with water retained by a cotton plug. claustralbrood raidingcompetition (Tschinkel 1992a, b). After addition of the queen(s),these were retained with a second Natural selection should optimize the trade-offbetween cotton plug in the mouth of the tube. The second type consisted of worker number and worker size (Porter and Tschinkel blocks of dental plaster 15 x 15 x 3 cm with 25 flat-bottomedholes 1986). Higher worker numbers favor success in brood 1.5 cm in diameter in a 5 x 5 array. Queens were placed into the raiding (Tschinkel 1992a) and colony growth rate holes in numberscalled for in the experimentaldesign. For labora- (Tschinkeland Howard 1983), while larger worker size tory use, the sides of the plasterblocks were waxed to reducedrying, and the plates were covered, top and bottom, with glass and held at favors worker longevity (Porter and Tschinkel 1985a), 30?C. Plates were moistened as needed. For field use, the plaster stress resistance and defensive value. In addition, the founding plates were unwaxed. queen must balance allocation of resourcesfor worker Data consisted of counts and weights of the contents of found- productionagainst those for maintenanceof herselfand ing nests. For several analyses brood were lumped into "young her brood, and perhapsalso for a reservefor post-claus- brood" consisting of eggs and first-instarlarvae, and "olderbrood" tral needs. consisting of the remaining larval instars, pupae and adult minim workers. These allocations are, of course,adjusted over evolu- Fat contents were determined by dry weight loss after ether tionarytime, but there is an indicationthat some adjust- extraction. Energy contents