Larger laboratory colonies consume proportionally less energy and have lower per capita brood production in Temnothorax
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Insectes Sociaux
RESEARCH ARTICLE
Larger laboratory colonies consume proportionally less energy and have lower per capita brood production in Temnothorax ants T. T. Cao • A. Dornhaus
Received: 1 December 2011 / Revised: 22 August 2012 / Accepted: 25 August 2012 / Published online: 11 September 2012 Ó International Union for the Study of Social Insects (IUSSI) 2012
Abstract Colony size can affect individual- and colonylevel behavioral and physiological traits in social insects. Changes in behavior and physiology in response to colony growth and development can affect productivity and fitness. Here, we used respirometry to study the relationship between colony size and colony energy consumption in Temnothorax rugatulus ants. In addition, we examined the relationship between colony size and worker productivity measured as per capita brood production. We found that colony metabolic rate scales with colony size to the 0.78 power and the number of brood scales with the number of workers to the 0.49 power. These regression analyses reveal that larger ant colonies use proportionally less energy and produce fewer brood per worker. Our findings provide new information on the relationships between colony size and energetic efficiency and productivity in a model ant genus. We discuss the potential mechanisms giving rise to allometric scaling of metabolic rate in ant colonies and the influence of colony size on energy consumption and productivity in general. Keywords Metabolic scaling Colony productivity Colony size Ants Temnothorax
T. T. Cao (&) A. Dornhaus Department of Ecology and Evolutionary Biology, University of Arizona, BioSciences West 310, 1041 E. Lowell St., Tucson, AZ 85721, USA e-mail: [email protected] A. Dornhaus e-mail: [email protected]
Introduction Social insect colonies can be highly dynamic and grow quickly to contain hundreds of workers in a short time. Changes in colony size can influence individual- and colony-level physiological and behavioral traits that affect colony efficiency and productivity (Karsai and Wenzel, 1998; Bourke, 1999; Anderson and McShea, 2001). In ants, species that have large colonies tend to show greater worker polymorphism (Ho¨lldobler and Wilson, 1990; Bourke, 1999), increased behavioral specialization (Oster and Wilson, 1978; Gautrais et al., 2002), and more complex communication behavior (Anderson and McShea, 2001; Mailleux et al., 2003). How do demographic and behavioral changes associated with colony size affect colony efficiency and productivity? One approach to answer this question is to study the energetic consequences of growth and correlate colony energy consumption with traits that are linked to efficiency and productivity such as brood production. Because reproductive fitness in social insects is a function of colony size (Hamilton, 1964; Oster and Wilson, 1978), studying the effects of colony size on energetics and productivity will provide information regarding group-level adaptations to population growth and their potential consequences
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