Ladybird beetles' life history traits

1. The balance between risk and benefit of exploiting resources drives
life history evolution in organisms. Predators are naturally recognized as
major drivers of the life history evolution of their prey. Although prey
may also influence the life history evolution of their predators in the
context of an evolutionary arms race, there is far more evidence of the
role of predators than of prey.  2. The goal of this study was to
investigate the role of prey in life history evolution of predators using
ladybird beetle predators of aphids and coccids. These particular
ladybirds and their prey were chosen because literature shows that the
pace of life of aphids is faster than that of coccids and this difference
is reflected in the life histories of the ladybirds that specialize on
feeding on aphids or coccids. 3. Thirty-four species of ladybird predators
of aphids and eight of coccids belonging to five different tribes were
collected and reared in the laboratory. The females were weighed as well
as their eggs, and their reproductive investment estimated as the number
of ovarioles. Phylogenetic relatedness was controlled for in the
statistical analyses. 4. Controlling for female mass revealed that
ladybird predators of aphids lay bigger eggs than ladybird predators of
coccids. This difference is not influenced by phylogenetic relatedness but
only by the type of prey eaten. We suggest that ladybird predators of
coccids lay smaller eggs because neonate larvae do not have to search,
catch, and subdue prey. Both types of ladybirds have a similar
reproductive investment relative to their body mass when phylogeny is
controlled for.  5. Recognizing the influence of prey on the life
history evolution of predators is important for understanding food web
dynamics. From an applied perspective, this fine evolutionary tuning of
prey-predator relationships should be used to guide and increase the
efficiency of biological control programmes.