Temperature-dependent survival, development, and adult longevity of the koinobiont endoparasitoid Venturia canescens (Hymenoptera: Ichneumonidae) parasitizing Plodia interpunctella (Lepidoptera: Pyralidae)

Abstract

The effect of various constant temperatures on survival, development, and adult longevity of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) parasitizing larvae of Plodia interpunctella Hübner (Lepidoptera: Pyralidae) was studied under laboratory conditions. The following temperatures were tested: 15, 17.5, 20, 22.5, 25, 27.5, 30, and 32.5°C. The percentage of parasitoids that completed development at each temperature as well as the days needed for the emergence of the parasitoid's pupa and adult eclosion was measured. Adult longevity was estimated under the same conditions. Survival of V. canescens was significantly higher at 25 and 27.5°C compared to 17.5, 20, 30, and 32.5°C. No individual of V. canescens managed to complete development at 15°C. Overall, developmental time decreased significantly with increasing temperature within the range of 17.5-27.5°C. The lowest developmental time was observed at 27.5°C while the highest at 17.5°C. Upper and lower threshold temperatures for total development were estimated at 36.2 and 13.2°C, respectively. Optimum temperature for development and thermal constant were 30.6°C and 312.5 degree days, respectively. Adult longevity was also affected by temperature, as it was significantly reduced at higher temperatures compared to the lower ones. This information would be useful in determining the potential of using V. canescens as a biological agent in IPM programs, by optimizing mass rearing and release techniques of the parasitoid.

Environmental degradation amplifies species’ responses to temperature variation in a trophic interaction

“…Resource limitation has been shown to increase life span in many taxa (reviewed in Szafranski & Mekhail, ), while, as with development time, temperature fluctuations have been reported to increase, decrease or to have no effect on adult life span in insects (Colinet et al, ). In our experiment, daily temperatures varied between 22.3 and 30.2°C, which exceeds Venturia's adult thermal tolerance (Spanoudis & Andreadis, ). Thermal acclimation during juvenile development could have increased thermal tolerance at the adult stage by reducing the costs of exposure to harmful temperatures in adults (Colinet et al, ; Slotsbo, Schou, Kristensen, Loeschcke, & Sorensen, ), but is unlikely to have prolonged adult life span further than under constant temperature as thermal acclimation is energetically costly (Krebs & Feder, ).…”

“…Resource limitation has been shown to increase life span in many taxa (reviewed in Szafranski & Mekhail, 2014), while, as with development time, temperature fluctuations have been reported to increase, decrease or to have no effect on adult life span in insects (Colinet et al, 2015). In our experiment, daily temperatures varied between 22.3 and 30.2°C, which exceeds Venturia's adult thermal tolerance (Spanoudis & Andreadis, 2012).…”

“…Short‐term temperature fluctuations that remain within the thermal tolerance range often accelerate juvenile development, but can also slow it in some species, or have no effects in others (reviewed in Colinet, Sinclair, Vernon, & Renault, ). Our results suggest that the host and parasitoid species differ in their sensitivity to fluctuating temperatures during the juvenile stage, despite having similar thermal optima and ranges of temperature tolerance (Spanoudis & Andreadis, ).…”

“…Resource degradation increases juvenile development time in both species (Boots, ; Harvey, Harvey, & Thompson, ), which increases the host's window of vulnerability to parasitism (Cronin, Reeve, Xu, Xiao, & Stevens, ), and decreases adult fecundity and the intensity of density‐dependent juvenile mortality, which dampens host and parasitoid generation cycles (Cameron, Wearing, Rohani, & Sait, ; Knell, Begon, & Thompson, ). Juvenile development of both species has similar thermal optima and ranges of thermal tolerance, but adult longevity is more sensitive to high temperatures in Venturia (Spanoudis & Andreadis, ). This model system provides an ideal proxy for trophic interactions in degraded habitats by reproducing dynamics frequently observed in natural populations (e.g.…”

“…Venturia (Spanoudis & Andreadis, 2012). This model system provides an ideal proxy for trophic interactions in degraded habitats by reproducing dynamics frequently observed in natural populations (e.g.…”