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Genetic caste determination does not impose growth rate costs in Pogonomyrmex harvester ants
Article first published online: 28 AUG 2009
DOI: 10.1111/j.1365-2435.2009.01629.x
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Additional Information
How to Cite
Cahan, S. H., Daly, A. B., Schwander, T. and Arthur Woods, H. (2010), Genetic caste determination does not impose growth rate costs in Pogonomyrmex harvester ants. Functional Ecology, 24: 301–309. doi: 10.1111/j.1365-2435.2009.01629.x
Publication History
- Issue published online: 26 FEB 2010
- Article first published online: 28 AUG 2009
- Received 21 April 2009; accepted 8 July 2009 Handing Editor: Frank Messina
- Abstract
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Keywords:
- caste determination;
- life-history trade-off;
- development;
- metabolic rate
Summary
1. Caste determination in eusocial insects is the process by which individuals differentiate into reproducer or helper phenotypes.
2. Environmental caste determination (ECD) is predicted to be more efficient than genetic caste determination (GCD), yet GCD occurs in several populations of Pogonomyrmex harvester ants.
3. We tested whether GCD reduces efficiency by comparing colony growth rates of two GCD lineage pairs (H and J) with two closely related ECD congeners, P. rugosus and P. barbatus, under laboratory conditions over a range of temperatures. In addition, we directly compared metabolic rates of GCD and ECD larvae using flow-through respirometry.
4. Unexpectedly, colonies from GCD lineages grew faster than colonies of P. rugosus across all temperatures, and grew at the same rate as colonies of P. barbatus. Slower colony growth rates of P. rugosus were caused by lower queen fecundity and slower larval development. Variation in developmental rate was not due to differences in larval metabolic rates, which did not differ among taxa.
5. These results suggest that GCD in Pogonomyrmex does not impose significant productivity costs during colony growth. Instead, efficiency costs are compensated by other physiological mechanisms which may or may not be directly related to the mode of caste determination.
6. Persistence of GCD populations in contact with ECD competitors likely stems from a life-history trade-off favouring different taxa across the geographic range of the complex: the slow growing but starvation-resistant P. rugosus dominates in resource-poor regions, while faster growing and competitive GCD populations predominate in more mesic habitats.