Reproductive competition between polygynous parasite queens in colonies Janni Larsen1, Terezinha M. Della Lucia 2, Morten Schiøtt1 and David R. Nash1 1Centre for Social Evolution, Department of Biology, University of Copenhagen, Denmark [email protected] 2Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-000 Viçosa, MG, Brasil Danish National Research Foundation Centre for Social Evolution

Introduction Social parasites are specialized in exploiting a complete society, rather than an individual organism. Among the most specialized social parasites are the inquilines that exploit social colonies. Inquiline social parasites are usually close relatives of their host and they must fully integrate into their host colony in order to reproduce. Most inquiline

have lost their sterile worker caste. Exceptions to this are insinuator and Acromyrmex ameliae,

parasites of fungus-growing ants. Studies have shown that a threshold proportion of parasite workers in the colony is essential for parasite reproduction. Multiple invasions of parasite queens into host colonies suggest that each parasite queen may need to produce fewer parasite workers and that the reproductive phase can be achieved more quickly. Polygyny among parasite queens is expected to select for intraspecific hyperparasitism, where some queens might cheat by only producing sexual offspring, effectively parasitizing the worker force produced by other queens. In this study we investigate hyperparasitism in A. insinuator by genotyping parasite offspring, workers and alates in polygynous nests to investigate any bias in the production of reproductive castes relative to workers. We also investigated infiltration techniques.

Reproductive competition In polygynous colonies intraspecific hyperparasitism may occur, where some queens cheat by only producing sexual offspring thereby effectively parasitizing the worker force produced by other queens. We analysed genotypes of 122 male alates and found intraspecific hyperparasitism between parasite queens where one parasite queen produces the majority of sexual offspring.

Host reproductive

1.0

0.8 oduced 0.6 p r

Parasite workers 0.4 of males Host colony rtion o 0.2 op P r

0.0 Queen 1 Queen 2 Proportion of male alates produced by the parasite queens Parasite queens Parasite reproductive

I nfiltration techniques Parasite queens were individually introduced into different sub-colonies (nestmate, non-nestmate without parasites, non- nestmate with parasites or allospecific) and the level of aggression and acce pt ance wi th which they were met were measured. We found that parasite queens were meet with less aggression and were more accepted in already parasitized colonies. . 2,2 BC ABC A BC 2,0 1.2 1,8 Nestmate Sub-colony 1 1,6

Non-nestmate + P

e 1,4 Non-nestmate - P an c t 0.8 1,2 e p Allospecific

Not accepted ac c 1,0 0.6 of 0,8 A g

r 0,6 0.4 e ss i oportion

on 0,4 P r i 0.2 nde x 0,2 0,0 0 Proportion of winged/wingless parasite gynes and parasite Aggression level of subcolonies (nestmate, non-nestmate + P, non- Accepted queens accepted into sub-colonies (nestmate, non-nestmate nestmate – P and allospecific) when introduced to parasite queens. +P, non-nestmate – P, and allospecific). Different letters indicate a significant difference (p < 0.05)

Conclusion

We found that parasite queens are more likely to be accepted and are met with le ss a ggression in al ready - parasitized colonies and that intraspecific hyperparasitism between parasite queens in pol ygynous c olonies d oes occur and one parasite queen produces the majority of sexual offspring and thereby che ats the other queen.

Acknowledgement: Thanks to all members of the Copenhagen Centre for Social Evolution.