Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination

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Serval ID
serval:BIB_36B9E6B0A120
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Evolution of social parasitism in ants: size of sexuals, sex ratio and mechanisms of caste determination
Journal
Proceedings of the Royal Society of London Series B-Biological Sciences
Author(s)
Aron  S., Passera  L., Keller  L.
ISSN
0962-8452
Publication state
Published
Issued date
01/1999
Peer-reviewed
Oui
Volume
266
Number
1415
Pages
173-177
Notes
162KX Times Cited:27 Cited References Count:35 --- Old month value: Jan 22
Abstract
Social parasitism, one of the most intriguing phenomena in ants, has evolved to various levels, the most extreme form being parasites that have lost the worker caste and rely completely on the host's worker force to raise their brood. A remarkable feature of workerless social parasites is the small size of sexuals. It has been suggested that reduced size evolved as a means to take advantage of the host's caste-determination system, so that parasite larvae develop into sexuals with less food than is required to produce host workers. An important consequence of size reduction is that it might restrict the host workers' ability to discriminate between the brood of the social parasite and their own brood and might protect parasite sexuals from elimination. We found that sexuals of the workerless inquiline ant Plagiolepis hene were significantly smaller than the sexuals of their host Plagiolepis pygmaea, but remarkably similar to the host workers. The size variance of parasite sexuals was much lower than that of their host; this result possibly suggests that there is very stabilizing selection acting on size of the parasite sexuals. Comparison of the primary (egg) and secondary (adult) sex ratios of the parasite and host showed that miniaturization of their sexuals has been accompanied by their ability to develop into sexuals even when the host P. pygmaea actively prevents production of its own sexuals. These results suggest that the inquiline's size and caste threshold have been reduced such that all individuals in a parasite brood will develop into sexuals. We also found that the adult sex ratio of P. xene was heavily female-biased. This bias probably stems from local mate competition that arises from sexuals mating within the nest. There was no significant difference between the proportion of haploid eggs and adult males produced; this observation indicates that a female-biased sex ratio is achieved by queens producing a higher proportion of diploid eggs rather than by a higher mortality of haploid males.
Keywords
social parasitism sex ratio local mate competition size variance caste threshold ant local mate competition argentine ant iridomyrmex-humilis adaptations hymenoptera allocation colonies workers
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Create date
24/01/2008 18:39
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20/08/2019 13:24
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