Data from: The price of insurance: costs and benefits of worker production in a facultatively social bee

Kin selection theory is foundational in helping to explain the evolution
of sociality; however, the degree to which indirect fitness benefits may
underlie helping behavior in species of early stage sociality has received
relatively little empirical attention. Facultatively social bees, which
demonstrate multiple forms of social organization, provide prime systems
in which to empirically test hypotheses regarding the evolutionary origins
of sociality. The subsocial small carpenter bee, Ceratina calcarata, may
establish a social nest by manipulating brood provisions to rear a worker
daughter, which then assists in critical late-season alloparental care.
Here, we combine nest demographic and behavioral data with genetic
relatedness estimates to calculate the relative inclusive fitness of both
subsocial and social reproductive strategies in C. calcarata. Social
mothers benefit from improved likelihood of brood survivorship and have
higher fitness than subsocial mothers. Worker daughters have low indirect
fitness on average, and will not produce their own offspring.
Among-sibling relatedness is significantly higher in social nests than
subsocial nests, though mothers of either reproductive strategy may mate
multiply. Though this study corroborates the ultimate role of indirect
fitness and assured fitness returns in the evolution of social traits, it
also offers additional support for maternal manipulation as the proximate
mechanism underlying evolutionary transitions in early stage insect
societies.