Do maternal allocations towards offspring quality and quantity ameliorate the effects of predators on offspring survival?

Reproductive allocation is often balanced between the quantity and quality
of offspring. Ecological stresses, like exposure to predators, can cause
organisms to shift their allocations along this continuum. While the
consequences of such plastic shifts for offspring performance are often
untested, they are critical to understanding the potential long-term
benefits of manipulating predation risk as an agricultural pest management
technique. Predation risk induces reductions in egg production
and increases in nutritional condition due to maternal provisioning in
Colorado potato beetles (Leptinotarsa decemlineata, CPB). Here we tested
whether reductions in density or increases in offspring condition, which
may increase per-capita larval survival, can compensate for the reduction
in total egg production, especially when offspring are exposed to
predators. In two field trials, we manipulated the density and
condition of larval CPB and measured survival through development to
adulthood in field cages with and without predaceous stink bugs (Podisus
maculiventris). As expected, cages with the higher initial larval
densities had more larvae and adults surviving in the treatments without
predators –about 30-50% survival across densities. When predators were
present this relationship did not hold because of density-dependent
predation. Larval condition interacted with density and impacted larval
survival in both trials albeit in different ways. In Trial 1,
unprovisioned beetles had higher survival at the higher densities, in
Trial 2 provisioned beetles had higher survival across densities.
Synthesis and Applications: Overall, our test of the effects of predation
risk via manipulations of larval density and condition revealed few net
compensatory benefits to the prey of reduced density and higher condition.
Benefits to the prey of shifts in allocation from the quantity to quality
of offspring may depend on factors that influence the strength of density
dependence, including predation intensity. Our results suggest a new
strategy of taking advantage of the reductions in prey density due to the
non-consumptive effects of predators as a pest management approach to
protect plants.