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1. Rearing temperature and parasitoid load determine host and parasitoid performance in Manduca sexta and Cotesia congregata

   https://doi.org/10.1111/een.12776  

   Moore, M. Elizabeth ; Kester, Karen M. ; Kingsolver, Joel G. ( July 2019 , Ecological Entomology)

   1. Temperature strongly influences the rates of physiological processes in insects, including the herbivoreManduca sextaand its larval endoparasitoidCotesia congregata. Parasitisation byC. congregatadecreases the growth and consumption of food by larvalM. sexta. However, the effects of temperature on parasitised caterpillars and the developing wasp larvae are largely unknown.

   2. In this study, parasitised and unparasitised caterpillars were reared at three constant temperatures (20, 25 and 30 °C) throughout larval development. Caterpillar mass gain and consumption were monitored daily until wandering (unparasitised control group) or wasp emergence (parasitised group) was observed. Development time and survival to emergence were measured as metrics of parasitoid performance.

   3. ParasitisedM. sextadeveloped more slowly than unparasitised controls, but had similar cumulative consumption until the terminal instar. Parasitised caterpillars with relatively large parasitoid loads had higher rates of consumption and growth than those with smaller loads. Both temperature and parasitoid load strongly affected wasp success. Mean development time to wasp emergence increased with low temperatures and with large loads. The combination of warm temperature and large parasitoid loads greatly reduced wasp survival.

   4. These results demonstrate the interactive effects of rearing temperature and parasitisation on host consumption and growth rates throughout larval development. In addition, wasp performance was affected by the interaction of temperature and parasitoid load size. High temperatures alter the dynamics of the interaction between the parasitoid and its caterpillar host, which could have far‐reaching impacts as the global temperatures continue to rise.

    

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2. Developmental timing of extreme temperature events (heat waves) disrupts host–parasitoid interactions

   https://doi.org/10.1002/ece3.8618  

   Moore, Megan Elizabeth ; Hill, Christina A. ; Kingsolver, Joel G. ( March 2022 , Ecology and Evolution)

   When thermal tolerances differ between interacting species, extreme temperature events (heat waves) will alter the ecological outcomes. The parasitoid waspCotesia congregatasuffers high mortality when reared throughout development at temperatures that are nonstressful for its host,Manduca sexta. However, the effects of short‐term heat stress during parasitoid development are unknown in this host–parasitoid system.

   Here, we investigate how duration of exposure, daily maximum temperature, and the developmental timing of heat waves impact the performance ofC.congregataand its host¸M.sexta. We find that the developmental timing of short‐term heat waves strongly determines parasitoid and host outcomes.

   Heat waves during parasitoid embryonic development resulted in complete wasp mortality and the production of giant, long‐lived hosts. Heat waves during the 1st‐instar had little effect on wasp success, whereas heat waves during the parasitoid's nutritionally and hormonally critical 2nd instar greatly reduced wasp emergence and eclosion. The temperature and duration of heat waves experienced early in development determined what proportion of hosts had complete parasitoid mortality and abnormal phenotypes.

   Our results suggest that the timing of extreme temperature events will be crucial to determining the ecological impacts on this host–parasitoid system. Discrepancies in thermal tolerance between interacting species and across development will have important ramifications on ecosystem responses to climate change.

    

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3. Effects of cold storage on life‐history traits of Aphidius matricariae

   https://doi.org/10.1111/eea.12958  

   Rezaei, Mehran ; Talebi, Ali_A ; Fathipour, Yaghoub ; Karimzadeh, Javad ; Mehrabadi, Mohammad ; Reddy, Gadi_VP ( August 2020 , Entomologia Experimentalis et Applicata)

   Aphidius matricariaeHaliday (Hymenoptera: Braconidae) is a polyphagous solitary endoparasitoid, attacking more than 40 species of aphids. This parasitoid is an important commercial product of many companies that produce biological control agents. Storage at low temperature increases the shelf life of many biocontrol agents, allowing companies to provide a steady and sufficient supply of insects for biocontrol programs. In the current study, the effects of cold storage of 1‐day‐old host mummies withA. matricariaefor various time periods (5, 10, 15, 20, and 30 days) at 5 °C on the parasitoid’s key life‐history traits were investigated. Parameters assessed after storage included adult emergence rate, offspring sex ratio, adult longevity, oviposition period, fecundity, and life‐table parameters (R₀, r, λ, T, and DT). Our results showed that the mummies ofA. matricariaecould be stored at 5 °C for 5 days without loss of quality and for 10–15 days with minimal reduction in quality (e.g., some reduction in adult longevity and R₀). If parasitoids were stored for >15 days, quality was more strongly affected. In conclusion,A. matricariaepupae could be stored at 5 °C for up to 15 days without significant negative post‐storage effects on fitness of the parasitoid. These results could be used to improve the planning of mass rearing and mass release ofA. matricariaein augmentative biological control programs.

    

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4. Causes and consequences of microbiome formation in mosquito larvae

   https://doi.org/10.1111/een.13360  

   Schwing, Cameron D ; Holmes, Christopher J ; Muturi, Ephantus J ; Dunlap, Christopher ; Holmes, Jessica R ; Cáceres, Carla E ( July 2024 , Ecological Entomology)

   The assembly of host‐associated microbial communities is influenced by multiple factors, but the effect of microbiomes on host phenotypes is often not well understood. To address questions of food‐web effects on host microbiome assembly, we manipulated the resource environment (grass only [G] vs. grass + nutrients [GN]), competition type (intra‐ vs. inter‐specific) and density (high vs. low) forCulex restuans mosquito larvae. We predicted the microbial communities in fourth‐instar larvae would differ between these environmental treatments and that these treatments would translate into differences in the adult phenotype.

   Resource environment and density influenced the larval microbiome. In addition, the larval microbiome exhibited notable differences compared to the free‐living microbial communities.

   Resource‐driven differences in the larval samples can be attributed to Arcobacteraceae being more abundant in larvae reared in the GN treatments relative to those reared in the G treatments and Comamonadaceae being more abundant in the G treatment. Although significant, the difference in community structure between density treatments was difficult to discern. This appears to be driven by Weeksellaceae only being abundant in the high‐density, interspecific, GN treatment.

   Rearing larvae to adulthood under severe food limitation resulted in low survival (<25%) in both resource environments. Approximately 60% of survivors to adulthood were male. Larvae reared in the intraspecific, G treatment had the shortest development time to adulthood and emerged as the smallest adults.

   These results demonstrate how environmental variation can significantly alter the alpha and beta diversity of free‐living microbes, which in turn can significantly affect host phenotype and critical life history traits, such as development time, size at adulthood, and survival. These findings highlight the importance of considering environmental influences on microbiome diversity to understand and predict host outcomes, offering valuable insights for diverse applications in fields such as ecology, public health, and agriculture.

    

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5. Host species differences in the thermal mismatch of host–parasitoid interactions

   https://doi.org/10.1242/jeb.245702  

   Malinski, Katherine H. ; Sorenson, Clyde E. ; Moore, M. Elizabeth ; Willett, Christopher S. ; Kingsolver, Joel G. ( June 2023 , Journal of Experimental Biology)

   ABSTRACT Extreme high temperatures associated with climate change can affect species directly, and indirectly through temperature-mediated species interactions. In most host–parasitoid systems, parasitization inevitably kills the host, but differences in heat tolerance between host and parasitoid, and between different hosts, may alter their interactions. Here, we explored the effects of extreme high temperatures on the ecological outcomes – including, in some rare cases, escape from the developmental disruption of parasitism – of the parasitoid wasp, Cotesia congregata, and two co-occurring congeneric larval hosts, Manduca sexta and M. quinquemaculata. Both host species had higher thermal tolerance than C. congregata, resulting in a thermal mismatch characterized by parasitoid (but not host) mortality under extreme high temperatures. Despite parasitoid death at high temperatures, hosts typically remain developmentally disrupted from parasitism. However, high temperatures resulted in a partial developmental recovery from parasitism (reaching the wandering stage at the end of host larval development) in some host individuals, with a significantly higher frequency of this partial developmental recovery in M. quinquemaculata than in M. sexta. Hosts species also differed in their growth and development in the absence of parasitoids, with M. quinquemaculata developing faster and larger at high temperatures relative to M. sexta. Our results demonstrate that co-occurring congeneric species, despite shared environments and phylogenetic histories, can vary in their responses to temperature, parasitism and their interaction, resulting in altered ecological outcomes. 

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