DOI: 10.5061/dryad.xwdbrv1ms
title: Do maternal allocations towards offspring quality and quantity ameliorate the effects of predators on offspring survival?

description: 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.
description: Using the herbivorous Colorado potato beetle and predaceous
 spined soldier bug system, we tested whether parental reproductive
 allocation shifts could compensate for reductions in the total number of
 eggs laid. In this system, mothers exposed to predators shift their
 reproductive investment to make fewer offspring with higher levels of
 provisioning. We tested 1) the individual and combined effects of larval
 density and condition on the number of offspring surviving to the last
 larval stage and emerging as adults, in the presence and absence of
 predators, 2) whether larval survival is density-dependent in the presence
 and absence of predators, and 3) whether density-dependent survival
 depended on larval condition. Lastly, 4) we measured larval feeding,
 growth, and development midway through the larval period to assess levels
 of competition and effects on plant damage. We placed
 larval beetles from all combinations of density and condition treatments
 in field mesocosms with and without predators. We then measured the number
 of beetles surviving daily throughout larval development and adult
 emergence and assessed beetle growth and plant damage early in the
 experiment. These experiments allowed us to determine the consequences of
 reproductive allocation for the local beetle population (total number
 surviving) and survival during larval development when the offspring were
 reared with or without predators.
description: # Do maternal allocations towards offspring quality and quantity
 ameliorate the effects of predators on offspring survival?
 [https://doi.org/10.5061/dryad.xwdbrv1ms](https://doi.org/10.5061/dryad.xwdbrv1ms) ## File 1: Ugine\_et\_al.\_2024\_1 ### Column headings and their meaning * Trial = two replicate tests of the same hypothesis (Trial 1 and Trial 2) * Cage = identity of the field mesocosm * Initial larval density = the number of first instar potato beetle larvae placed into the cage (larvae/cage) * Provisioning = low are unprovisioned beetles, high were provided sibling eggs to consume * Predator presence = Yes indicates we placed *Podisus maculiventris* in the cage, and No indicates no predators added to the cage. * Day 0, initial mass (grams) = the mass of the initial cohort of beetle larvae placed into the cage (co-variate) * Abundance day 1-9 = number of larvae remaining in the cage via visual inspection (larvae/cage on day n) * Number of 4th instars (d6-d9) = the number of fourth instars we observed on plants in a given cage 6, 7, 8, or 9d post-initiation of the trail. * Number of larvae weighed (4d) = the number of larvae in a group that we used to estimate larval growth over the first 4d of each Trial. * Group mass (4d)(grams) = the mass of the group of larvae from the “Number of larvae weighed (4d)” column * average mass per beetle (4d)(grams) = Group mass dividide by number of larave weighed (4d) * Total damage per cage = estimates of square cm of leaf tissue consumed by larvae during the first 4d of each trial. * Prop., 4ths (d6-d9) = Number of 4th instars divivded by cage total of the same day. * Sum beetle days 1-4 = Sum of larval abundance on days 1-4. * Damage per beetle days (cm^2 damage/sum of beetle days 1-4) = Total damage per cage divided by sum of beetle days * Number of emerged adults = number of new adult beetles emerging within each cage over the three weeks after the last larva was observed on a plant. Notes: * Missing cell values in Group Mass and Average Mass per beetle occur when there are no larvae in the cage to weigh. These cells should be left blank for analyses. * Missing cell values in Prop 4ths (d6-d9) occur when the proportion of 4th instars and the number of larvae in the cage are both 0; 0/0=undefined. These cells should be left blank for analyses. ## File 2: Ugine\_et\_al.\_2024\_2 ### Column headings and their meaning * Trial =two replicate tests of the same hypothesis (Trial 1 and Trial 2) * Cage = identity of the field mesocosm * Density = the number of first instar potato beetle larvae placed into the cage (larvae/cage) * Provisioning = low are unprovisioned beetles, high were provided sibling eggs to consume * Predator presence = Yes indicates we placed *Podisus maculiventris* in the cage, and No indicates no predators added to the cage. * Day 0, initial mass = the mass of the initial cohort of beetle larvae placed into the cage (co-variate) * Beetles per cage = count of live larvae per cage * day = indicates what day the “Beetles per cage” were made on * Proportion surviving = beetles per cage divided by density ## Sharing/Access information NA ## Code/Software We used JMP Pro V.16 to perform all of the statistical analyses. Our statistical approach is outlined in detail in the Statistical Methods section of the manuscript.