Egg production and caste allocation in the clonally reproductive ant Vollenhovia emeryi

Sex ratio theories based on relatedness asymmetries among colony members have been tested in eusocial Hymenoptera. The haplodiploid sex determination system leads to differences in optimal sex allocation between queens and workers. Queens should ideally produce sexual eggs in accordance with relatedness asymmetries. One of the methods to test this hypothesis is to examine sex allocation in species where relatedness asymmetries are extremely different between female and males produced by the queens. We investigated sex allocation patterns in the polygynous ant Vollenhovia emeryi where both sexes are produced clonally so that the relatedness of the queens to their female and male offspring is 1.0 and 0, respectively. In this situation, queens invest most of their resources in female production. Furthermore, caste allocation patterns were observed in egg production. This study involved genotype analysis of colony members using genetic polymorphic markers and revealed clonal reproduction in the V. emeryi population. In this population, castes were identified in 1,060 eggs produced by 70 queens in 8 colonies. Queens invested more resources in female sexual eggs, though male eggs were also produced depending on resource availability. In addition, the proportion of female eggs negatively correlated with that of worker eggs, suggesting that this correlation is a trade-off. However, male egg production did not affect the egg production of other castes. This observation indicates that male egg production is independent of that for other castes. This study is the first to document the real primary sex ratio and caste allocation in eusocial Hymenoptera. Copyright 2010, Oxford University Press.