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

Citation

Stowe, Hannah; Michaud, JP; Kim, Tania (2022), Resource amount and discontinuity influence flight and reproduction in Hippodamia convergens (Coleoptera: Coccinellidae), Dryad, Dataset, https://doi.org/10.5061/dryad.7m0cfxpx6

Abstract

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.

Methods

Reproductive data was collected by collecting and counting all eggs laid by participating lady beetle females on each day. Egg clutches were retained and hatch was also quantified. Flight data was collected using an automated infrared sensor with an Arduino and terminal program to collect and store tethered insect flight mill revolution data. The Flight output data was processed from the original text file output into an excel document and processed to remove extraneous lines and rows. Access was used to ensure ease of analysis and to allow for the use of queries. Raw data has then been processed to consist of lists of revolution time stamps rather than binary revolution/no revolution event data.

 

Usage Notes

Microsoft Excel is required, Microsoft Access will be useful. All analysis was done in R studio. 

Funding

U.S. Department of Agriculture, Award: 2018-67013-28060

U.S. Department of Agriculture, Award: 58-3091-6-035