Advantages of multiple foundress colonies in Belonogaster juncea juncea L.: greater survival and increased productivity

Abstract.  1. The ecological hypothesis predicts that multiple foundress colonies of social wasps may have a better survival rate and produce more brood per capita than single foundress colonies. With the aim of verifying if these characteristics exist in the primitively eusocial wasp species Belonogaster juncea juncea (L.), we monitored 49 foundations, including 13 single and 36 multiple foundress colonies, in Cameroon.
2. Multiple foundress colonies were significantly more successful than single foundress colonies in producing at least one adult.
3. The total productivity of the colonies increased significantly with the number of associated foundresses, but the productivity per capita did not. No single foundress colony reached the sexual phase, while eight (21.6%) multiple foundress colonies did. Males were produced in only five colonies, so that the sex ratio was biased in favour of females.
4. These results suggest that because of the strong ecological constraints on solitary nesting, survival and high colony productivity are two advantages of multiple foundress colonies in B. j. juncea .
5. The decreasing per capita productivity concomitant with an increasing number of females noted in this study illustrates once again Michener's paradox. The coefficient of variance of the per capita productivity significantly decreased with group size, as Wenzel and Pickering suggested in the model they created to explain the paradox.
6. Ecological factors may act in conjunction with other factors, such as genetic relatedness between associated foundresses, to promote joining behaviour in B. j. juncea .