Resource amount and discontinuity influence flight and reproduction in Hippodamia convergens (Coleoptera: Coccinellidae)

Industrial-scale agriculture creates a mosaic of large monocultures in the
landscape, where seasonal cropping cycles generate discontinuous resource
availability for insect predators both spatially and temporally. In this
environment, selection will favor predator movement and reproductive
behaviors that optimize the location and effective utilization of resource
(prey) pulses that are both patchy and ephemeral in nature. Using a model
system to study predator movement and reproduction, we tested how
discontinuous periods of food resource access that mimic fluctuating
resource populations (aphids) would influence flight behavior and
reproduction of a highly mobile predator, Hippodamia convergens
(convergent lady beetle), and possibly modify energetic trade-offs between
these behaviors. Examining how these factors affect reproduction and
movement in a lab context is an important first step toward understanding
their corresponding performance in the field. Adult beetles were provided
either short (3h) or long (6h) food pulses daily (continuous availability)
or short (6h) or long (12h) food pulses every other day (discontinuous
availability). We measured pre-oviposition period, fecundity, and
fertility during an 18-day oviposition period, and female tethered flight
activity (3h) before and after the oviposition period. We found that
discontinuous food access delayed the onset of oviposition in the high
food quantity treatment; fewer females laid eggs overall, and 18-d
fecundity was lower compared to continuous provision of the same food
quantity. A longer pre-oviposition period was associated with fewer
reproductive days and lower fitness. Flight distance and fecundity were
negatively correlated, suggesting that energetic expenditure in flight can
deplete energetic reserves otherwise used for subsequent reproduction. The
negative fitness effects of discontinuous resource access at fine temporal
scales reveal how similar gaps in resource availability could influence
lady beetle population dynamics and their ecosystem services within the
agricultural landscape. Understanding how resource availability patterns
affect lady beetle fitness and behavior can inform agricultural land
management strategies to enhance their biological control services.