Genetic diversity and lifespan of transplanted colonies

Selection may favour traits throughout an individuals lifetime or at a
particular life stage. In many species of social insects, established
colonies that are more genetically diverse outperform less diverse
colonies with respect to a variety of traits that contribute to fitness,
but whether selection favours high diversity in small colonies is unknown.
We tested the hypothesis that selection favours genetically diverse
colonies during the juvenile period using a multi-year field experiment
with the harvester ant, Pogonomyrmex occidentalis. We used controlled
matings to generate colonies that varied in genetic diversity and
transplanted them into the field. We monitored their survival for seven
(the 2015 cohort, N = 149) and six (the 2016 cohort, N = 157) years.
Genetically more diverse colonies had greater survival, resulting in
significant viability selection. However, in both cohorts survival was not
influenced by genetic diversity until colonies were three years old. We
suggest that changes in their internal organization enabled colonies to
use the benefits of multiple genotypes, and discuss possible mechanisms
that can generate this pattern. The accompanying data give the number of
patrilines, the date of transplant and the number of years that the colony
survived.